ORGANIC CHEMISTRY1. INTRODUCTIONSTEADY development is reported this year in many branches of organicchemistry. The use of high-speed computers has facilitated the complexcalculations necessary for progress in applying quantum organic chemistryto complex structures. There has been much interest, both theoreticaland experimental, in the spectroscopic and other properties of carboniumions. Kinetic isotope effects continue to be an extremely important toolin elucidating the nature of the rate- and product-controlling steps ofchemical reactions, and many applications, both to hererolytic and tohomolytic processes, have been noted.An important series of papers has appeared dealing with the mechanismsof nitrosation by the nitrosonium ion and its carriers. Arylpentazoles havebeen obtained by the reaction between aromatic diazonium chlorides andlithium azide, and some of their properties have been studied.Nuclear and proton magnetic resonance spectroscopy continue to havemany applications in organic chemistry; among them is the location ofsubstituents in furan rings and in N-heteroaromatic systems and the deter-mination of the ring fusion of decalins.A new heterocyclic aromaticsystem, containing the -NH:BH- groups in positions 9,10 of phenanthrene,has been described. Important stereospecific syntheses in the yohimbineand reserpine series of alkaloids have been reported, and there has beenmuch progress in the chemistry of the curare alkaloids.Interest in synthetic and naturally occurring polyenes and poly-ynes hascontinued, and a naturally occurring polyene chlorohydrin has beenidentified.There is an increasing emphasis on both the biogenesis and thelaboratory synthesis of terpenes. Partially demethylated triterpenes havebeen discovered and the " biogenetic gap" between the steroids andtriterpenes reduced.Among outstanding advances reported in the field of nucleic acids areincluded the recognition that these substances are generally mixtures ofdifferent species varying in molecular weight and possibly also in nucleotidesequence; the isolation of several purine bases not formerly recognised ascomponents of naturally occurring nucleic acids; and the synthesis of someoligodeoxynucleotides. In the section dealing with carbohydrates themain stress is laid this year on developments in the chemistry of poly-saccharides.+ -T.G. H.P. B. D. DE LA M.2. QUANTUM ORGANIC CHEMISTRYONE of the truisms of quantum chemistry is that, since the fundamentallaws of electron quantum mechanics are known, chemical problems are alCRAIG : QUANTUM ORGANIC CHEMISTRY. 169in principle soluble by calculation, and that nothing stops the solutions’being obtained but the sheer complexity of the equations that have to besolved. Up to the last few years the complexity was almost always avoided,and the equations were drastically altered into simpler ones that could besolved without too much trouble. Simplification of the quantum-mechanicalequations corresponds to making assumptions about the physical characterof the system (such as assuming that nuclear motion does not affect theelectron energies in a molecule), and the calculations, usually empirical, thenrefer to a “ model ” system which has some, but not all, of its properties incommon with the real system.Everything hinges on making the rightsimplifying assumptions to get answers close to the physical ones.It is possible to discern two trends in current attitudes. High-speedcomputing enables very complex calculations to be made quickly, and somakes possible an altogether new range of exact theoretical studies of simplemolecules, as well as approximations (for example by M.O. methods) tolarge ones. Then, in regard to model studies, much more attention is beingpaid to the techniques for incorporating the empirical quantities, such asspectral intervals or ionization potentials, that go into the calculations.This not only leads to better results but also often reduces the amount ofcalculation by which the results are obtained from the starting data; itimproves the illustrative value of the model, allowing one to form a picturemore readily of the physical processes which make the real system behaveas it does.Moreover it lightens the problems of finding answers by theoreti-cal methods to practical problems, such as the colour to be expected of ahitherto unknown hydrocarbon. Although much important progress hasbeen made along these lines of finding the most fruitful and simple ways ofintroducing experimental values of one quantity into the calculation ofanother, much scope remains for similar ingenuity, for example, in calcul-ations of dipole moments and spectral intensities, which are not yet in agood state.Still more remains in the field of reactivity and reaction be-haviour, which are essentially two- or many-system problems and so are ofan altogether greater difficulty. Significant progress in the latter field wasdescribed in the last Rep0rt.lIn the two-year period under review about 350 papers in which quantummechanics are applied to organic molecules have been listed in CurrentChemical Papers. A large majority deal with the properties of aromaticmolecules and other x-electron systems, for example, the electron distri-bution in the ground state and the electronic absorption spectrum.Therehas been important progress in the methods used for hydrocarbons, in theirrapid extension to nitrogen-heterocycles, to the negative and positivearomatic ions, and to the calculation of ionization potentials. Smallergroups of the papers reflect sustained interest in new theories of the electronicstructure of the simplest organic molecules, radicals, and ions, in hyper-conjugation, in the potential harrier in ethane, and in the interpretation ofnuclear magnetic resonance and electron spin resonance spectra. An in-creasing but still small number of papers deal with reactivity and substitutionby employing theories, now having some significant successes, which treatAnn. Reports, 1966, 63, 126170 ORGANIC CHEMISTRY.transition states by means of localization energies or similar concepts, insteadof ground-state properties such as electron densities.In this Report mention will be made of the main fields of enquiry, butsuch is the volume of published work that the individual papers quoted areoften only representative of a large number generally similar in method oroutlook.In the period since thelast Report the development described there concerning semi-empiricaltheories of x-electrons has continued, some new variations of method havebeen described, and many applications have been made to individual mole-cules.When non-empirical calculations (A.S.M.O.) of the spectra ofx-electron systems are properly completed by including configurationalinteraction (C.I.),3,4 they give fairly good agreement with experiment forcertain types of molecular states, but appear to under-estimate the stabilityof others that have a high degree of ionic character, such as the lBlu andlElu states of benzene.W. E. Moffitt concluded that the prime difficultylay in the calculated size of purely intra-atomic energy terms, such as thedifferences of binding energy between trigonally hybridized C+, C, and C-,and he gave a semi-empirical theory (“ atoms in molecules,” A.I.M.) inwhich calculated differences between these quantities were replaced byexperimental values, the other energy terms being obtained non-empiricallyas before. Much subsequent work has confirmed the value of the centraltheme of the A.I.M. method, namely, that the non-empirical element incalculations of this kind should be confined to interatomic effects, but it hasshown also that the results are very sensitive to the way in which the empiri-cal quantities are brought in.Hurley showed that the original techniqueowed its good account of the binding energy of H, to a cancellation of errorsand has investigated some other difficulties. Arai7 has treated the samequestion. Hurley * and Arai have now independently proposed new waysof making the intra-atomic energy correction. Both give better results, ata certain cost in added complication. The “ intra-atomic correlation cor-rection ” (I.C.C.) of Hurley, and the “ deformed atoms in molecules ”(D.A.I.M.) of Arai have been described and critically compared in a recentre vie^.^ ,Of the modified methods, only I.C.C. (in a simplified form) hasso far been applied to a x-electron sy.stem,l0 and the results set against thosefrom A.I.M.and A.S.M.O. with configuration interaction.* In A.I.M. theintra-atomic correction in benzene was found by comparing the differencebetween the ionization potential and the electron affinity of an isolatedcarbon atom in its trigonally hybridized valence state with the differencebetween the same quantities calculated by using Slater orbitals appropriate%-Electron Theory.-Semi-em$iricaZ methods.M. Goeppert-Mayer and A. L. Sklar, J. Chem. Phys., 1938, 6, 645.a D. P. Craig, Proc. Roy. SOC., 1950, A , 200, 474. * R. G. Parr, D. P. Craig, and I. G. Ross, J . Chem. Phys., 1950, 18, 1561.No.49, p. 40.N. Polgar, J., 1958, 430.R. E. Harman, Quart. Rev., 1958, 12, 93WHITHAM : ALIPHATIC COMPOUNDS. 229tram-pentaene chromophore. Mild oxidative degradation has led to aproposal 80 of the partial structure (33). One of the degradation pro-ducts (34) has also been obtained from the pentaene antibiotic fungichromin.slthereby indicating a probable structural similarity. Several other polyeneantifungal antibiotics are known which may well be of related structure.82O-CO-CarH,r-lsO~=~(OH)Me*CH.CH(OH)fCH=CH],*CH=CMe*CH*OH OHC*[CH=C H],*C H=CMe*CHO I(33) (34)Oleandomycin appears to be a macrolide antibiotic of the more conven-tional type , containing glycosidically bound desosamine and ~-0leandrose.~~The lactones heptanolide and octanolide have been prepared by aBaeyer-Villiger reaction of peroxytrifluoroacetic acid with cyclohexanoneand cycloheptanone respectively.@Nitrogen Derivatives.-A novel synthesis of isocyanides involves treat-ment of formamides in pyridine with toluene-$-sulphonyl chloride 85 orphosphorus oxychloride.86 The Beckmann rearrangement of ketoximebenzenesulphonates in the presence of hydrogen sulphide affords thiocarboxy-amides ; these are also obtained from N-substituted carboxyamides byconsecutive treatment with benzenesulphonyl chloride, pyridine , andhydrogen ~ulphide.~~ Further work on naturally occurring isothiocyanatesis reported.=9.HETEROCYCLIC COMPOUNDSReviews.-Naturally occurring furans, the lichen acids, oxygen-hetero-cyclic fungal metabolites ,3 lignans from PodophyZZ~m,~~ hydroxy-flavansand -flavensJ4b brazilin and h~ematoxylin,~ the products obtainable fromketones, ammonia, and sulphur,6 0xazolidine-2,4-diones,~ melamine,*a andrecent work on pyridazines Sb have been reviewed.The proceedings of twosymposia on heterocyclic chemistry have been publi~hed.~General.-Nuclear quadrupole resonance spectroscopy has been applied loto the study of the electronic structures of heterocyclic compounds, andproton magnetic resonance spectroscopy to the detection and location ofsubstituents in furan ringsu In studies of the tautomerisrn of numerousN-heteroaromatic compounds, cc- and y-hydroxy-compounds have beenfound to be predominantly amidic.12Interest in new aromatic systems is illustrated by the synthesis l3 of the9-aza-lO-bora-derivative (1) of phenanthrene and its substitution products107 J.A. Zderic, A. Bowers, H. Carpio, and C. Djerassi, J . Amer. Chem. SOC., 1958,108 R. M. Dodson and R. D. Muir, ibid., 1958, 80, 5004.80, 2596.1 J. Levisalles, Perfumery Essent. Oil Record, 1958, 49, 504, 627.2 C. A. Wachmeister, Svensk kem. Tidskr., 1958, 70, 117.3 W. B. Whalley, Progr. Org. Chem., 1958, 4, 72.4 (a) J. L. Hartwell and A. W. Schrecker, Fortsclzr. Chern. org. Naturstofle, 1958,15,84; (b) K. Freudenberg and K. Weinges, ibid., 1958,16, 1.5 (Sir) R. Robinson, Bull. Soc. chim. Frunci, 1958, 125.F. Asinger and M. Thiel, Angew. Chem., 1958, 70, 667; cf. Ann. Reports, 1957,54, 242.7 J. W. Clark-Lewis, Chern.Rev., 1958, 58, 63.8 (a) B. Bann and S. A. Miller, ibid., 1958, 58, 131; (b) J. Druey, Angew. Chem.,1958, ‘SO, 5.Q “ Current Trends in Heterocyclic Chemistry,’’ ed. by A. Albert, G. M. Badger,and C. W. Shoppee, Buttenvorths, London, 1958; “ Les He’t6rocycles OxygCnCs,”C.N.R.S., Paris, 1947.10 M. J. S. Dewar and E. A. C. Lucken, J., 1958, 2653.l1 E. J. Corey, G. Slomp, S. Dev, S. Tobinaga, and E. R. Glazier, J . Amer. Chew.12 S. F. Mason, J., 1957, 4874, 5010; 1968, 674.13 M. J. S. Dewar, V. P. Kubba, and R. Pettit, J., 1958, 3073, 3076.Soc., 1958, 80, 1204286 ORGANIC CHEMISTRY.and of various five-membered ring systems containing boron. The formerclosely resemble phenanthrenes spectroscopically. In the same connexion,although the compounds are not heterocyclic, the greatest interest attachesto the demonstration that phenylpentazole is formed in the reaction betweenbenzenediazonium chloride and lithium azide. The arylpentazoles areunstable, though some have been obtained crystalline and their ultravioletspectra have been recorded.14Small Rings.-Oxazirans 15a are the initial products of irradiatingnitrones,lbb and have been used as a source of nitrosoalkanes.15" A newmethod for preparing epoxides of +unsaturated ketones,16 and means ofdetermining the stereochemistry of epoxy-ethers and their ring-openedderivatives have been described.17 Structures of the type (2) (from deoxy-benzoin) have been confirmed l8 for the desaurins " formed from ketonesand carbon disulphide in the presence of bases.( 3 )Five-membered Rings.-Pyrroles.Extensive ultraviolet and infraredspectroscopic studies of pyrroles have been presented.lg Diels-Alderaddition occurs between acetylenedicarboxylic acid and l-benzylpyrrole ; 20that between benzyne and l-methylpyrrole 21 gives the bases (3) and finally(4). With ally1 bromide, potassiopyrrole unexpectedly gives 2- rather thanl-allylpyrrole.22 The primary products of reaction between pyrroles andninhydrin, alloxan, or isatin are alcohols such as (5), which acids convertinto dyes. Reaction with two mols. of these reagents produces compoundsin the manner of (6). The yellow product from proline andninhydrin has the structure (7), and the purple-red product is (Q).M 2-Methylpyrrole is responsible for most of the colour produced by Ehrlich'sreagent in the Elson-Morgan assay of hexosamine~.~~ Examination of the14 R.Huisgen and I. Ugi, Chem. Ber., 1957, 90, 2914; I. Ugi and R. Huisgen, ibid.,15 (a) Ann. Reports, 1957, 54, 240;' (b) J. S. Splitter and M. Calvin, J . Org. Chem.,16 N. C. Yang and R. A. Finnegan, J . Amer. Chem. SOC., 1958, 80, 5845.17 C. L. Stevens and T. H. Coffield, J . Org. Chem., 1958, 23, 336; C. L. Stevens and18 P. Yates and D. R. Moore, ibid., p. 5577.19 U. Eisner and P. H. Gore, J., 1958, 922; U. Eisner and R. L. Erskine, ibid., p.20 L. Mandell and W. A. Blanchard, J . Amer. Chem. SOC., 1957, 79, 6198.21 G. Wittig and W. Behnisch, Chem. Ber., 1958, 91, 2358.22 P. A. Cantor and C. A. VanderWerf, J .Amer. Chem. SOC., 1958, 80, 970.23 A. Treibs, E. Herrmann, and E. Meissner, Annulen, 1958, 612, 229.24 A. W. Johnson and D. J. McCaldin, J., 1958, 817.25 J. W. Cornforth and (Mrs.) M. E. Firth, ibid., p. 1091.1958, 91, 531; I. Ugi, H. Perlinger, and L. Behringer, ibid., p. 2324.1958,23, 651; (c) W. D. Emmons, J . Amey. Chem. SOL, 1957, 79, 6522.A. J. Weinheimer, J . Amer. Chem. SOC., 1958, 80, 4072.971SCHOFIELD AND SWAIN : HETEROCYCLIC COMPOUNDS 287diazo-coupling reactions of a range of pyrroles shows an order of reactivityin line with the electronic characters of substituents, greater reactivity in1-methylpyrrole than in pyrrole, and the failure of some a-unsubstitutedpyrroles to react when powerful electron-attracting substituents are0-(7)0present.26 3-Hydroxypyrroles show no ketonic properties and give onlysome hydroxyl reactions; C-acylation occurs more readily than 0-acylation .27In hot, slightly alkaline solution, acetamidoacetaldehyde gives 3-acet-amidopyrrole.28 The Schiff’s bases from p-keto-esters and esters of cc-amino-acids are cyclised to 3-hydroxypyrroles under Dieckmann condition^.^^Tetracyanoethylene reacts with pyrrole to give tricyano-2’-pyrrylethylene,and is a prolific source of pyrroles and other heterocyclic compounds. It isconverted by sodium sulphide into 2,5-diamino-3,4-dicyanothiophen whichundergoes base-catalysed rearrangement to 5-amino-3,4-dicyanopyrrole-2-thiol. Tricyanovinyl compounds R*C(CN)=C(CN), (for example, R = Ph)give, with thiols R’SH, the pyrroles (9).30Pyoluteorin, an antibiotic from Pseudomonas aemginosa, is a pyrrolederivative (lo) .31 X-Ray studies indicate structure (11) for kainic (digenic)acid,32” the chief anthelmintic from the seaweed Digenea simplex Agardh.32b26 A.Treibs and G. Fritz, Annalen, 1958, 611, 162.27 A. Treibs and A. Ohorodnik, ibid., p . 149.28 J. W. Cornforth, J . , 1958, 1174.29 A. Treibs and A. Ohorodnik, Annalen, 1958, 611, 139.30 T. L. Cairns, R. A. Carboni, D. D. Coffman, V. A. Engelhardt, R. E. Heckert,E. L. Little, E. G. McGeer, B. C. McKusick, W. J. Middleton, R. M. Scribner, C. W.Theobald, and H. E. Winberg, J . Amer. Chem. SOC., 1958, 80, 2775 et seq.31 R. Takeda, ibid., p . 4749.32 (a) H. Watase and I. Nitta, Bull. Chem. SOC. Japan, 1957, 30, 889; (b) S.Mura-kami, T. Takemoto, and 2. Shimizu, J . Pharm. SOC. Japan, 1953, 73, 1026; 1954, 74,560288 ORGANIC CHEMISTRY.Furans. Commercially available 2-methylallyl chloride and butane-1,2,4-triol have been used as sources of 3-substituted fur an^.^^Bullatenone from Myrtus buZZata, originally thought to be a y-pyrone, is2,3-dihydro-2,2-dimet hyl-3-oxo-5-phenylfuran .34 Details of the synthesisof (&)-ipomeamarone (12), and discussions of its chemistry,published.35CH2.CHMe2H Hhave been(13)Thiophens. 2-Vinylthiophen undergoes diene addition with maleicanhydride and benzoquinone, as does 3-vin~lthionaphthen.~~ Derivativesof the type (131, formed by high-dilution cyclisation, can be desulphurised tocyclic hydrocarbons or ketones3' Mono-olefins give not only polysulphideswith sulphur, but also cyclic products.2,6-Dimethylocta-2,6-diene withsulphur at 140" gives several reduced thiophens, and similar compounds (14)arise by cyclising ketones R*CH(SH)*CH2*CH2*COMe.381-Phenyl-5-prop-l-ynylthiophen has been isolated from Coreopsis g r a d -AxoZes. With phosphorus pentachloride 4-nitrosopyrazoles give inter-mediates R*C(Cl)=N*N=C(CN)R, which are cyclised by ammonia to 5-amin0-3,6-disubstituted-1,2,4-triazine~.~~Deuteration of imidazole is pH-controlled, proceeding initially at the4,5-positions in deuterium oxide alone, but at position 2 in the presence ofsodium deuteroxide.4l The blue pigment formed by oxidising glycosin(2,2'di-imidazolyl) with hydrogen peroxide is the di-N-oxide (15) .42 Thehighly reactive carbonyldi-l-imidazole 43a has been used in peptide synthesis,since with carboxylic acids it gives l-acylimidazoles which provide amideswith a m i n e ~ .~ ~ ~33 H. Wynberg, J . Amer. Chem. Soc., 1958, SOj 364; J. W. Cornforth, J . , 1958, 1310.34 W. Parker, R. A. Raphael, and D. I. Wilkinson, J., 1958, 3871.35 T. Kubota and T. Matsuura, J., 1958, 3667; T. Kubota, Tetrahedron, 1958, 4,36 W. Davies and Q. N. Porter, J., 1957, 4958.37 Ya. L. Gol'dfarb, S. 2. Taits, and L. I. Belen'kii, Izvest. Akad. Nauk S.S.S.R.,Otdel. khim. Nauk, 1957, 1262.38 L. Bateman, R. W. Glazebrook, C. G. Moore, M. Porter, G. W. Ross, a i d R. W.SaviIle, J., 1958, 2838; L. Bateman, R. W. Glazebrook, and C. G. Moore, ibid., p.2846; L.Bateman and R. W. Glazebrook, ibid., p. 2834.39 J. S. Sorensen and N. A. Sorensen, Acta Chem. Scand., 1958, 12, 771.40 R. Fusco and S. Rossi, Tetrahedron, 1958, 3, 209.4 1 A. Grimison and J. H. Ridd, PVOC. Chem. SOC., 1958, 256; R. J. Gillespie, A.Grimison, J. H. Ridd, and R. F. M. White, J., 1958, 3228.42 R. Kuhn and W. Blau, Annalen, 1958, 615, 99.43 (a) Ann. Reports, 1957, 54, 243; (b) G. W. Anderson and R. Paul, J . Auner. Chem.~ Z O Y U .3968; T. Kubota and T. Matsuura, Bull. Chem. SOC. Japan, 1958, 31, 491.SOL, 1958, 80, 4423SCHOFIELD AND SWAIN : HETEROCYCLIC COMPOUNDS. 289Six-membered Rings.-Pyridines and piperidines. Infrared data onmany derivatives of pyridine and pyridine 1-oxide are now available.P4Sulphonation of pyridine in presence of mercuric sulphate at 275" givesmainly pyridine-3-sulphonic acid, but at higher temperatures some 4-isomer and 4-hydroxypyridine are also f0rmed.4~ The product obtained 46by oxidising pyridine-4-thiol with nitric acid is not pyridine-4-sulphonicacid, but di-4-pyridyl disulphide dinitrate.47 4-Fluoropyridine is unstable'at ordinary temperatures, rapidly giving a pyridylpyridinium compound.2-Fluoropyridine, unlike the other 2-halogenopyridines, behaves similarly.48Arenesulphonyl chlorides react with 4-methyl- or 4-ethyl-pyridine in thepresence of a tertiary base to give sulphones (16; R = H or Me).49" Azidinium '' salts (17; one form shown) (similar products can be made inthe thiazole, benzothiazole, thiadiazole, and quinoline series), obtained from2-chloro-1-ethylpyridinium borofluoride and azide ions, behave like diazon-ium salts.With dialkylamines they give tetrazens, and with azides givetriazacarbocyanines.m Hydrazinium salts (18), prepared from pyridinequaternary salts containing reactive 4-substituents, undergo oxidativecoupling with phenols in the presence of ferricyanide, and with dialkyl-anilines in an oxidising acidic sol~tion.~l 1,2-Di-(6-brornomethyl-2-pyridy1)ethane is converted in moderate yield by butyl-lithium into di-(pyridine-2,6-dimethylene) (19), which, like di-m-xylylene, may have a" stepped " structure.52 2-Vinylpyridine hydrobromide is converted byheat into the compound (20), which with piperidine forms 1-(2-2'-pyridyl-ethyl) ~iperidine.~~Mercuric acetate causes 2- and 2,6-substitution in pyridine N-oxide, andnot 4-sub~titution.~ The N-oxide quaternary salt (21) is converted byalkali into 2-vinylpyridine and formaldehyde, but the reaction of the lower44 A.R. Katritzky, A. M. Monro, and (in part) J. A. T. Beard, D. P. Dearnaley, andN. J. Earl, J., 1958, 2182; A. R. Katritzky and J. N. Gardner, J., 1958, 2192, 2198;A. R. Katritzky and A. R. Hands, J., 1958, 2195, 2202; A. R. Katritzky, J., 1958,4162.45 H. J. den Hertog, H. C. van der Plas, and D. J. Buurman, Rec. Trav. chim.,1958, 77, 963.46 E. Koenigs and H. Kinne, Bey., 1921, 54, 1357.47 J. Anguli and A. M. Muricio, Chenz. and Ind., 1958, 1175; A. M. Comrie and J. B.4a J.-P. Wibaut and W. J. Holmes-Kamminga, Bull.SOC. chim. France, 1958, 424.413 2. Foldi, Chenz. and Id., 1958, 684.so H. Balli, Angew. Chem., 1958, 70, 442.61 S. Hiinig and G. Kobrich, Annalen, 1958, 617, 181, 216; S. Hunig, Angew. Ckem.,Se W. Baker, K. M. Buggle, J. F. W. McOmie, and (in part) D. A. M. Watkins, J.,63 V. Boekelheide and W. Feely, J . Amer. Chem. Soc., 1958, 80, 2217.54 M. van Ammers and H. J. den Hertog, Rec. Truv. chim., 1958, 77, 340.Stenlake, J., 1958, 1853.1958, 70, 215.1958, 3594.REP.-VOL. LV 290 ORGANIC CHEMISTRY.quaternary homologue is complex.53 2-Phenylpyridine N-oxide is nitrated10-100 times faster than 2-phenylpyridine, and the reaction with this oxideand 4-phenylpyridine N-oxide produces more of the m-nitro-compound thanis the case with the non-oxygenated derivative^.^^ Selenium dioxide reactsmore quickly with 4- than with 2-methylpyridine, and these oxidations areretarded if the picolines are present as quaternary salts or N-oxides.A$methyl group is not attacked.56With ethoxide, hydroxyl, or cyanide ions a number of 3-substitutedpyridinium salts form pseudo-bases, probably at the 6-po~ition.~' Protonmagnetic resonance spectroscopic studies of deuterated dihydro-N-methyl-nicotinamide, formed by reducing nicotinamide methiodide in deuteriumoxide, confirm the 1,4-dihydropyridine structure of these models of diphos-phopyridine nucleo tide.58 Dithionite reduction of 3,5-dicarbamoyl- 1- (2,6-di-chlorobenzy1)pyridinium bromide gives an intermediate formulated as(22; R = CH,*C6H,C1,), which with acid is converted into the correspond-ing 1,4-dihydropyridine; it' is suggested that the formation of 1,4-di-hydro-compounds in natural coenzyme reductions may proceed throughinitial 1,2-additi0n.~~ Nuclear magnetic resonance studies indicate thatthe diethyl dihydro-1,2,6-trimethylpyridine-3,5-dicarboxylate, previouslythought to be a 1,2-dihydro-compound, is in fact the 1,4-isomer: thisevidence throws doubt upon the diagnostic tests believed to distinguish1,2- from 1,4-dihydro-structure~.~~ Methohalides of pyridine and alkyl-pyridines are generally reduced by sodium borohydride to a mixture ofpiperidines and A3-piperideines.62 As well as the expectedcyclopentylamines, piperidines result from the reduction oftertiary nitrocyclopentanes with lithium aluminium h ~ d r i d e .~ ~The antibiotic, fusarinic acid, 5-n-butylpyridine-2-carboxylicacid, has been synthesised from 2,6-lutidine; 64 and baikiain(23), the amino-acid from Rhodesian teak heartwood, byDiaxines. Pyrimidine undergoes 3,4-addition reactions with aryl55 A. R. Hands and A. R. Katritzky, J., 1958, 1754.56 D. Jerchel, J . Heider, and H. Wagner, Annalen, 1958, 613, 153; see also D.57 A. G. Anderson, jun., and G. Berkelhammer, J . Org. Chem., 1958, 23, 1109.58 R. F. Hutton and F. H. Westheimer, Tetrahedron, 1958, 3, 73.59 K. Wallerfels and H. Schiilz, Angew. Chem., 1958, 70, 471.60 A. F. E. Sims and P. W. G. Smith, Proc. Chem. SOC., 1958, 282.61 Ann. Reports, 1957, 54, 245.62 M. Ferles, Coll. Czech. Chem. Comm., 1958, 23, 479.63 G.E. Lee, E. Lunt, W. R. Wragg, and H. J. Barber, Chem. and Ind., 1958, 417;G. E. Lee, W. R. Wragg, S. J. Corne, N. D. Edge, and H. W. Reading, Nature, 1958,181, 1717.64 E. Hardegger and E. Nikles, Helu. Chim. Ada, 1957, 40, 2428.R5 N. A. Dobson and R. A. Raphael, J., 1958, 3642.C02H(23)H 0cyclisation of the cis-olefin BzN*CH,*CH:CH*CH,*CHBrCO,H.~Jerchel and H. E. Heck, ibid., p. 171SCHOFIELD AND SWAIN : HETEROCYCLIC COMPOUNDS. 291Grignard and lithium reagents : hydrolysis and oxidation of the productsgive 4-arylpyrirnidines.66 Some 4-hydroxypyrimidines react with chloralto give, after hydrolysis, 4-hydro~ypyrimidine-5-aldehydes.~~ Pyrazinegives mono- and di-N-oxides, whilst pyrimidine and pyridazine appear toform only mono-derivatives.66y 68Oxygen heterocycles.6-Substituted a-pyrones have been synthesisedfrom 2-chlorovinyl ketones and ethoxymagnesiomalonic ester.69 With N-bromosuccinimide, dihydropyran gives a mixture of 5-bromo-3,4-dihydro-2H-pyran, 2,3-dibromotetrahydropyran, and 3-bromotetrahydro-2-succin-imidopyran.70 A re-investigation of the action of acrylonitrile and p-bromo-propionic acid on kojic acid showed that no new product is formed;potassium cyanide yields the cyanohydrin.71 Monoarylmethylene derivativesof 2,6-dimethyl-4-pyrone are obtained in good yield by using potassiumhydroxide as condensing reagent. Acylation of the pyrone in presenceof zinc chloride in boiling xylene gives 3-acyl or diacyl derivatives,further cyclisation occurring with laevulic acid to yield the bicyclic com-pound (24) .72Anibine (25; R = 3-C5H,N) and 4-rnethoxyparacotoin (25; R = 3,4-CH,O,:C,H,) have been isolated from and the structure of theformer compound confirmed by synthesis.74Large Rings.-Dibenzamil, the compound obtained by decomposingphenyl azide in aniline, has the structure (26) (or a double-bond isomer).',Interest in the chemistry of oxepin (27) is shown by the synthesis of2,3,6,7-, and 2,3,4,7- te trahydro-oxepin , and of dibenz [b, f] oxepin and its2-nitro-derivative.7666 H.Brederick, R. Gompper, and H. Herlinger, Angew. Chem., 1958, 70, 57.67 R. Hull, J., 1957, 4845.68 W. H. Gumprecht, Diss. Abs., 1958, 18, 64.69 N. K. Kochetkov and L. I. Kudryashov, Zhur. obshchei Khim., 1958, 28, 1511.7O J.R. Shelton and C. Cialdella, J . Org. Chem., 1958, 23, 1128.7l C. D. Hurd and S . Trofimenko, J. Amer. Chem. SOC., 1958, 80, 2526.72 L. L. Woods, ibid., p . 1440.7 3 0. R. Gottlieb and W. B. Mors, ibid., p. 2263.74 E. Ziegler and E. Nolken, Monatsh., 1958, 89, 391.75 R. Huisgen, D. Vossius, and M. Appl, Chem. Ber., 1958, 91, 1 ; R. Huisgen andM. Appl, ibid., p . 12.76 J. Meinwald and H. Nozaki, J . Amer. Chem. SOC., 1958, 80, 3132; S. Olsen andR. Bredoch, Chem. Be?., 1958, 91, 1589; J. D. Loudon and L. A. Summers, J., 1957,3809292 ORGANIC CHEMISTRY.Condensation of f uran with ace tone gives oct ame thy1 te traoxaquatereneOxidation of dithiols +-C,H,(O*[CH,],=SH), by air in the presence ofcupric ions gives the cyclic disulphides (29). An interesting attempt tomake “ daisy-chain ” molecules by such cyclisations of the inclusion com-pounds from the dithiols and dextrin failed.78Polypyrroles and Related Compounds.-The use of permanganate oxida-tion in conjunction with paper-chromatographic analysis of the resultingpyrrole acids is a useful degradative tool in the porphyrin field.Thediscovery of the triacid (30) in the oxidation products of phaeophorbide aand mesophEophorbide a is not easily understood in terms of Fischer’ss t r u c t ~ r e s . ~ ~ Application of the method to a number of bile pigments showsthat all the common members of this group possess the “ IX-cc ” structure,being derived from biliverdin.80 Chromic acid oxidation of stercobilin 81provides confirmation for the structure (31 ; P = CH,*CH,*CO,H) suggestedfor this compound by Birch 82 and indicates for durobilin the expression (32).(28; x = 01.77Fischer’s structure for bacteriochlorophyll receives support from dehyd-rogenation studies of the derived bacteriochlorin-e, trimethyl ester and thecopper derivative of the acetyl~hlorin.~~ Treatment of the pyrrole ester (33)with lead tetra-acetate (a reagent which, as would be expected, gives theacetoxymethyl 84385 and not the hydroxymethyl derivative *,), followed byhydrogenolysis and boiling in acetic acid, led to the isolation of copro-porphyrin I11 triethyl ester (as 34) with only traces of isomers.Similarlythe triethyl ester (35) gave uroporphyrin I11 (36) as the chief product.87 Anew mechanism to account for the conversion of 2-(substituted methyl)-SAXTON: ALKALOIDS.306acetate,16 and from the infrared spectrum l6?l7 in the region 2800-2700cm.-l. Dehydrogenation of matrine or allomatrine with mercuric acetategives, in addition to the normal dehydro-base, a hydroxydehydro-derivative(3),16 which can be hydrogenated to a mixture of stereoisomers. One ofthese, sophoranol (4), is a constituent of the roots of SoPhora flavescens.18The position of the hydroxyl group in hydroxylupanine (5) and baptifolinehas been rigorously established by conversion of the former into 13-ax-hydroxysparteine, which was identified by total synthesis. This series oftransformations involved epimerisation of the 13-substituent ; hence in thesealkaloids the hydroxyl group has the equatorial conformation.lgPyridine Group.-The conformations of conhydrine 2oj 21 and pseudo-conhydrine2Z23 have been deduced.The former belongs to the erythro-series, and C(2) corresponds to the L-amino-acids, hence it can be formulatedas (6). In pseudoconhydrine (7), the hydroxylated carbon atom belongsto the DG series, while C(2) corresponds to the D-amino-acids.(-)-Homostachydrine, the methyl betaine of (-) -pipecolic acid, occursin alfalfa (Medicago sativa), and is frequently a contaminant of stachydrineisolated by the usual extraction procedure^.^^Quinoline Group.-Eduleine, the alkaloid of Casimiroa edulis, has beenidentified as 7-methoxy-l-methyl-2-phenyl-4-quinolone, which also occursin Lunasia a m a ~ a .~ ~ Two syntheses of evolitrine, and two further synthesesof dictamnine, have been reported.26Isoquinoline Group.-The Russian contributions to the elucidation andsynthesis of the Ipecacuanha alkaloids are summarised in a recent article.27A further non-stereospecific synthesis of (&)-emetine, similar in principleto the earlier Russian synthesis, has been reported.28 Comparison of anintermediate in this synthesis with material obtained from cincholoipon ethylester, in which the substituents in the piperidine ring are known to be cis,has confirmed that the 10- and ll-substituents are trans oriented in emetine(8).29 The evidence relating to the conformation of the 1’-hydrogen atomhas been variously interpreted,29, 30 but axial hydrogen seems more likelysince emetine is stable to strong bases (Wolff-Kishner conditions), and hydro-genation of the methyl ester corresponding to (9) gives almost exclusivelythe tertiary base possessing the same stereochemistry as emetine.30 Theseconclusions regarding its stereochemistry have been confirmed by the firststereospecific synthesis of (-)-emetine, which also embraces the totall7 F.Bohlmann, Chem. Ber., 1958, 91, 2157.F. Bohlmann, D. Rahtz, and C. Arndt, ibid., p. 2189.F. Bohlmann, E. Winterfeldt, and H. Brackel, ibid., p. 2194.2o J. Sicher and M. Tichy, Chem. and I n d . , 1958, 16.21 R. K. Hill, J . Amer. Chem. SOC., 1958, 80, 1609.22 Idem, ibid., p. 1611.23 K. Balenovic and N. Stimac, Croat. Chem. Acta, 1957, 29, 153.24 G.Wiehler and L. Marion, Canad. J . Chem., 1958, 36, 339.F. Sondheimer and A. Meisels, J . Org. Chem., 1958, 23, 762.26 R. G. Cooke and H. F. Haynes, Austral. J . Chem., 1958, 11, 225; T. Sato and27 R. P. Evstigneeva and N. A. Preobrazhensky, Tetrahedron, 1958, 4, 223.29 A. Brossi, A. Cohen, J. M. Osbond, P. A. Plattner, 0. Schnider, and J. C. Wickens.30 A. R. Battersby, ibid., p. 1324.M. Ohta, Bull. Chem. SOC. Japan, 1957,30, 708; 1958, 31, 161.M. Barash and J. M. Osbond, Chem. and Ind., 1958, 490.ibid., p. 491306 ORGANIC CHEMISTRY.syntheses of psychotrine and ceph~eline.~~ The crucial stages in this synthesisinvolve trans-addition of diethyl malonate to the dihydropyridone [lo; R =CH,*CH,*C,H,(OMe),], hydrogenation of the ester (9) to give the productcontaining axial hydrogen, and hydrogenation of (+)-O-methylpsychotrine(8, with C,l,N double bond), to give mainly (-)-emetine (8), togetherwith some of the l-epimeric (-)-isoemetine.EtSeveral other synthetic investigations in the isoquinoline field have alsobeen completed; syntheses of (-J-)-~tephanine,~% (&)-crebanine,s and( j-)-corydine have been recorded.Indole Group.-The perennial grass, PhaZaris arundinacea L., contains5-metho~y-Nb-rnethyltryptamine.~ Psilocybin, the psychotropic principleof the Mexican fungus, Psdocybe mexicana, and several other Psilocybespecies, has been shown by degradation and synthesis to have structure (11) ;this is the first recorded example of a phosphorylated indole derivative, andthe first 4-hydroxylated tryptamine derivative to be isolated from naturalA Russian synthesis of yohimbine, from the previously synthesisedyohimbone, has been claimed, but little or no confirmatory evidence has beenprovided; infrared spectra and rotations are not quoted, and the meltingpoints of intermediates are not always in close agreement with publishedvalues, where a~ailable.~' An outstanding contribution to indole alkaloidchemistry is the total stereospecific synthesis of pseudoyohimbine by vanTamelen and his collaborators.38 The starting material was the adductfrom 9-benzoquinone and butadiene (12), which was converted into(+)-pseudoyohimbine (13) by the reactions shown in the Chart.Sincepseudoyohimbine has already been converted into yohimbine (14), the total31 A.R. Battersby and J. C. Turner, Chem. aud Ind., 1958, 1324.32 D. H. Hey and A. Husain, J., 1958, 187633 T. R. Govindachari, K. Nagarajan, and C. V. Ramadas, J., 1958, 983.34 D. H. Hey and A. L. Palluel, J., 1957, 2926; N. Arumugam, T. R. Govindachari,35 S. Wilkinson, J., 1958, 2079.36 A. Hofmann, R. Heim, A. Brack, and H. Kobel, Exfierientia, 1958, 14, 107; A.37 L. A. Aksanova and N. A. Preobrazhensky, Doklady Akad. Nawk S.S.S.R.,36 E. E. van Tamelen, M. Shamma, A. W. Burgstahler, J. Wolinsky, R. Tamm,K. Nagarajan, and U. R. Rao, Chem. Ber., 1958, 91, 40.Hofmann, A. Frey, H. Ott, T. Petrzilka, and F. Troxler, ibid., p. 397.1957, 117, 81.and P. E. Aldrich, J . Amer. Chem. SOC., 1958, 80, 6006SAXTON : ALKALOIDS. 307synthesis of the latter is also complete.This synthesis also constitutes aformal synthesis of P-yohimbine (17-epimer of yohimbine), since this can beobtained from yohimbine by several methods, the simplest of which involvesdirect isomerisation of the axial 17-hydroxyl group to the more stable0 H C. H 2 C.'-hOH7,MeO,C*"OH ('3) O*CHOReagents: I , Zn-AcOH, then CI*CH,*CO,Et.KOBut, then saponification, then decarboxylation,then Ag,O. 2 , COCICOCI, then tryptamine. 3, OsO,, then Pt-H,, then HIO,. 4, H,PO,-H,O,then MeOH-HCI, then LiAIH,. 5, Hydrolysis of lactol e t h e r , then acetylation, then eliminationof AcOH. 6 , OsO,, then HIO,. 7, Hydrolysis, then Cr0,-H,SO,-MeOH, then (-)-camphor-sulphonic acid.equatorial conformation by means of potassium t - b ~ t o x i d e .~ ~ Additionof the elements of methanol to apoyohimbine yields p-yohimbine methylether,40 while reduction, by potassium borohydride, of yohimbinone (theOppenauer oxidation product of yohimbine under appropriate conditions)gives p-y~himbine.~~ A novel method proceeds through the previouslyunknown yohimbic acid lactone, obtained by reaction of yohimbic acid withethyl chloroformate ; this on acetolysis furnishes p-yohimbine acetate.41In a memorable communication full details of the synthesis of reserpineby Woodward and his co-workers have been published.42 Two independentA. Le Hir and E. W. Warnhoff, Compt. rend., 1958, 246, 1564.40 W. 0. Godtfredsen and S . Vangedal, A d a Chem. Scand., 1957, 11, 1013.41 P. A. Diassi and C.M. Dylion, J . Amer. Chem. SOC., 1958, 80, 3746.42 R. B. Woodward, F. E. Rader, H. Bickel, A. J. Frey, and R. W. Kierstead, Teira-hedron, 1958, 2, 1308 ORGANIC CHEMISTRY.syntheses of the degraded corynantheine-type alkaloid, flavopereirine, havealso been described.43In relation to the possible mode of biosynthesis of oxygenated yohimbineand deserpidine derivatives, it is noteworthy that the microbiologicaloxidation 44 of certain yohimbine analogues in the presence of cultures ofCunninghamella blakesleana or Streptomyces aureofaciens leads to hydroxyl-ation at position 10 or 18. Mainly on the basis of spectrographic evidence,and on molecular-rotation analogies between a-yohimbine and seredine, thelatter is formulated as 10,11-dimethoxy-a-yohimbine.45The unique a-orientation of the 15-hydrogen atom in ajmalicine andcorynantheine, and of the biogenetically equivalent 4-hydrogen atom incinchonamine has been demonstrated by conversion of ajmalicine intodihydrocorynantheane, and of corynantheine and cinchonamine into thecommon degradation product (15) .& Since dihydrocinchonidine has recentlybeen converted into dihydrocin~honamine,~~ this stereochemical identityalso applies to position 4 of the major Cinchona alkaloids.Re-examination of mitraphylline (16) has confirmed that it is the oxindoleTs = p-C,H4Me-S0,analogue of ajmalicine ; the constitution (16) includes tentative speculationsregarding its stereochemistry.Uncarine-A and -B are regarded as stereo-isomers of mitraphylline.48 Closer investigation of the alkaloids of Taber-nunthe iboga has revealed the presence of three new alkaloids, together withvoacangine; 49 the isolation of the last base confirms the relationship of theTabernanthe and the Voacanga alkaloids, previously demonstrated by theconversion of voacangine into ibogamine.Stemmadenia Donnell-Smithii, the first member of this species to beinvestigated, also contains both Tabernanthe and Voacanga alkaloids,4s A.Le Hir, M.-M. Janot, and D. Van Stolk, Bull. SOC. chim. France, 1958, 551;I<. B. Prasad and G. A. Swan, J., 1958, 2024.44 W. 0. Godtfredsen, G. Korsby, H. Lorck, and S. Vangedal, Experientia, 1958, 14,88; S. C. Pan and F. L. Weisenborn, J . Amer. Chem. Soc., 1958, 80, 4749.45 J.Poisson, N. Neuss, R. Goutarel, and M.-M. Janot, Bull. Soc. chim. France,1958, 1195.46 E. Wenkert and N. V. Bringi, J . Amer. Chem. Soc., 1958, 80, 3484.47 E. Ochiai and M. Ishikawa, Pharm. Bull. (Japan), 1957, 5, 498.48 J. C. Seaton, R. Tondeur, and L. Marion, Canad. J . Chem., 1958, 36, 1031; T.49 D. F. Dickel, C. L. Holden, R. C . Maxfield, L. E. Paszek, and W. I. Taylor, J. Nozoye, Ann. Report ITSUU Lab., 1958, 9, 66.Amer. Chem. SOC., 1958, 80, 123SAXTON : ALKALOIDS. 309together with (+)-quebrachamine and a new base, ~ternmadenine.~~ Afurther new alkaloid from Voacanga africana, voacangarine, is probably ahydroxyvoacangine (17; R = CO,Me, R’ = OH), since saponification,decarboxylation, and treatment with toluene-P-sulphonyl chloride inpyridine gave a hexacyclic quaternary salt (18); reduction of this withsodium and ethanol gave a mixture of bases, among which ibogaine (17;R = R = H) was identified.51 A closely related alkaloid, iboxygaine, hasrecently been extracted from an Iboga species; this could be 21-hydroxy-ibogaine (17; R = H, R’ = OH), but it is formulated as its 20-hydroxy-isomer, since it is reported to contain C-methyl and to give the iodoformreaction. Reaction with toluene-P-sulphonyl chloride gave a quaternarysalt, for which the constitution (18) is also p o s t ~ l a t e d .~ ~Full details are now available of the selenium dehydrogenation ofibogaine, ibogamine, and tabernanthine,53 and of the synthesis of theproducts obtained from ib0garnine.~4 Additional degradations of thesealkaloids have also been described ; a particularly interesting sequenceinvolved preparation of the related indoxyl, e.g., (19) from ibogamine, whichwas then converted into the toluene-9-sulphonyl derivative of its oxime.When this was heated in aqueous pyridine cleavage of the molecule occurredto give anthranilonitrile and the tricyclic ketone (20), which was furtherdegraded to S-ethyl-6-rnethylq~inoline.~~The earlier report that aspidospermine contains an N-methyl group hasbeen shown to be erroneous; this deduction was based on an atypicalnuclear magnetic resonance spectrum, and on an unreliable (in this series)Herzig-Meyer detemination. The formation and cleavage of aspidosper-mine [14C]methiodide to give inactive aspidospermine excludes the presenceof an N-methyl group.The von Braun degradation of this alkaloid is nowinterpreted 55 as indicating that the environment of Nb is (-CH,),N*CH<.Two brief reviews summarise recent work by Schmid,Karrer, and their collaborator^.^^ The progress in this immensely com-plicated group during the current year has been spectacular, and muchclarification has been achieved. The quaternary carboline alkaloidmavacurine has been converted into the related indoxyl, fluorocurine. Theintermediate dihydroxymavacurine has been identified as C-alkaloid Y ,57hence it is also referred to as C-profluorocurine. The shift to longer wave-lengths of the ultraviolet maxima of C-alkaloid Y, calebassine (C-toxiferineII), and other alkaloids, in alkaline solution is now attributed to an N,-carbinolamine, or vinylogous, grouping ; in the case of calebassine, this hasbeen confirmed by the preparation of the corresponding methyl ether.58Curare grozlp.50 F. Walls, 0.Collera, and A. Sandoval, Tetrahedron, 1958, 2, 173.51 D. Stauffacher and E. Seebeck, Helv. Chim. A d a , 1958, 41, 169.52 R. Goutarel, F. Percheron, and M.-M. Janot, Compt. rend., 1958, 246, 279.63 M. F. Bartlett, D. F. Dickel, and W. I. Taylor, J . Amer. Chem. Soc., 1958, 80,54 H. B. MacPhillamy, R. L. Dziemian, R. A. Lucas, and M. E. Kuehne, ibid.,p. 2172.86 H. Conroy, P. R. Brook, M. K. Rout, and N. Silverman, ibid., p. 5178.50 P. Karrer, H. Schmid, K. Bernauer, F. BerIage, and W. von Philipsborn, Angew.Chem., 1958, 70, 644; P.Karrer, Bull. SOC. chim. France, 1958, 99.57 H. Fritz, T. Wieland, and E. Besch, Annalen, 1958, 611, 268.58 K. Bernauer, H. Schmid, and P. Karrer, Helv. Chim. Acta, 1958, 41, 673.1263 10 ORGANIC CHEMISTRY.The identification of caracurine VII with the Wieland-Gumlich aldehyde(21; R = OH) provides the first rigorous proof that the alkaloids of theSouth American Strychnos species belong to the strychnine type, and is ofspecial interest in connection with the role attributed to this aldehyde inthe biosynthesis of these alkaloid^.^^ The Nb-methosalt of (21; R = OH)also occurs in calebash curares,a while C-curarine I11 (C-fluorocurarine) isbelieved to be the corresponding quaternary salt of (21; R = H) with a2,le-double bond. The importance of the Wieland-Gumlich aldehyde inthis series is emphasised by its isolation from the acid degradation ofcaracurine Va (nortoxiferine-I) ; similarly, toxiferine-I gives the corres-ponding Nb-methosalts.60y 62 The re-synthesis of caracurine Va and toxi-ferine-I from these fission products establishes the constitution of these“ dimeric ” alkaloids; caracurine Va is (22; R = OH), and toxiferine-I isthe related bis-quaternary compound.The conversion of ‘* heminor-dihydrotoxiferine ” and the Wieland-Gumlich aldehyde into a commonderivative proves that the former has structure (21 ; R = H) ; consequently,“ nordihydrotoxiferine ” is represented by (22; R = H), and dihydro-toxiferine is the corresponding bis-quaternary compound.62Lochneram, the Nb-methyl quaternary derivative of lochnerine, has beenisolated from Rio Negro curares, and characterised as the tetraphenyl-boronate; it is curious that ozonolysis gives only acetaldehyde, whileauthentic lochnerine, as well as lochnerine prepared from lochneram, giveboth acetaldehyde and f~rmaldehyde.~~Pyrrolizidine Group.-Crotalaria retusa L., a poisonous Australian weed,contains several alkaloids, among which retusine, hitherto unknown, isformulated as (23), since hydrolysis gives the amino-alcohol (24) and twoepimeric acids of structure (25) A related species, Crotalaria spectabilis60 K.Bernauer, S. K. Pavaranam, W. von Philipsborn, H. Schmid, and P. Karrer,8o A. R. Battersby and H. F. Hodson, Proc. Chem. SOC., 1958, 287.61 W.von Philipsborn, H. Meyer, H. Schmid, and P. Karrer, Helv. Chim. Ada,e2 K. Bernauer, H. Schmid, and P. Karrer, ibid., p. 1408; K. Bernauer, F. Berlage,63 W. Arnold, F. Berlage, K. Bernauer, H. Schmid, and P. Karrer, i f i d . , p. 1505.64 C . C. J. Culvenor and L. W. Smith, Austral. J . Chew?., 1957, 10, 464, 474.Helv. Chim. A d a , 1958, 41, 1405.1958, 41, 1257.W. von Philipsborn, H. Schmid, and P. Karrer, ibid., p. 2293SAXTON : ALKALOIDS. 311Roth., contains monocrotaline and spectabiline, which is an acetylmono-crotaline.64(-)-Heliotridane has been converted by successive Hofmanndegradations and hydrogenations into (+)-3-methylheptane. Accordingly,the absolute configuration of (-)-heliotridane is as shown in (26;. R = H),and in isoretronecanol as in (26; R = OH).65 These conclusions arecontrary to those obtained by application of molecular-rotation arguments.66nCH.CH2RRH2f:HCPhenanthridine Group.-Several new alkaloids have been added to thisgroup during the year under review.67 Progress in the structural investig-ations in this field is mainly due to Wildman and his co-workers.De-gradation of hzmanthamine has afforded N- (4,5-methylenedioxy-2-phenyl-benzy1)glycine and 4-4'-methoxycyclohexyl-5-methyl-1,2-methylenedioxy-benzene, identical with the product of hydrogenation of dihydrotazettinemethine. Hence, hzmarithamine has formula (27; R = OMe, R' = H), andthe stereochemistry of ring c is the same as that of tazettine.68 Crinamineis probably its 3-methoxy-epimer.Hzmanthidine, earlier assumed topossess the tazettine skeleton, is now believed to be represented by (27;R = OMe, R' = OH) ; this formulation is in better accord with its properties,e.g., the oxidation of dihydrohaemanthidine to a bridged lactam, which, frompreliminary observations, behaves as an amino-alcohol rather than a normall a ~ t a m . ~ ~ In this series several interesting transformations have beeneffected by means of sodium and pentyl alcohol, which eliminates aryl- orallyl-methoxyl gr0ups.~0 For example, hzmultine, a new base fromHamanthus multiflorus, is formulated as (27; R = R' = H), since it can beobtained by demethoxylation of hzmanthamine and ~rinamine.7~ Similarly,65 F. L. Warren and M. F. von Klemperer, J., 1958, 4574.66 N.J. Leonard, Chem. and I n d . , 1957, 1455.13' H. G. Boit and W. Dopke, Naturwiss., 1958, 45, 85; H. G. Boit, W. Dopke, andW. Stender, ibid., p. 262; L. Paul and H. G. Boit, Chem. Ber., 1958,91, 1968; L. J. Dry,M. Poynton, M. E. Thompson, and F. L. Warren, J., 1958, 4701.68 H. M. FaIes and W. C. Wildman, Chem. and I n d . , 1958, 561.6Q S. Uyeo, H. M. Fales, R. J. Highet, and W. C. Wildman, J . Amer. Chenz. Soc.,1958, 80, 2590.70 H. M. Fales and W. C . Wildman, ibid., p. 4395.'l H. G. Boit and W. Dopke, Chem. Ber., 1958, 91, 1966312 ORGANIC CHEMISTRY.falcatine is an ar-methoxycaranine, while narcissidine probably has structure(28; R = OH, R’ = OMe), since demethoxylation gives, among otherproducts, pluviine (28; R = R’ = H).70The ethanophenanthridine skeleton of crinine has been established byits conversion into crinane (29; R = H), which was also ~ynthesised.~,I(27) R‘RThe position of the hydroxyl group in crinine was confirmed 72 by Hofmanndegradation of oxocrinine, which yielded an optically inactive methinebase (30).Consequently, crinine is represented as (29; R =OH, with a1,2-double bond) ; powelline is an ar-methoxycrinine, and buphanisine andbuphanidrine are the corresponding 3-methyl ethers.72 Finally, undulatinehas been shown to be the epoxide of buphanidrine.73Erythrinu Group.-Synthetic support for the constitution of a-erythroidinehas been provided by the synthesis of two degradation products (31 ; R = 0)and (31; R = :CH*CH-CH,*OH). Since both CC- and p-erythroidine can bedegraded to the same diene, these two alkaloids only differ in the positionof a double bond; in confirmation, it has been shown that a-erythroidine(32) is isomerised to p-erythroidine by hot alkali.74Diterpene Group.-Two reviews, one concerning the Delphinium alkaloids,and another the Aconite-Garrya alkaloids, are welcome additions to alkaloid1iterat~x-e.~~ One of the remaining doubtful structural features of atisineis the position of the ally1 alcohol system; this has now been located as in(33) by elimination of C(7) and the methylene group, to give a 8-keto-acid.The final product (34; R = 0) of this degradation is of interest, since theacid (34; R : H,) should be obtainable from the Garrya alkaloids and thusafford a method for interrelating these two series.76 Further evidence insupport of this structure is provided by the selenium dehydrogenation of anisoatisine derivative, which affords 6-isopropyl-l-methylphenanthrene, andby synthesis of 6-ethyl-l-methyl-3-azaphenanthrene (35), the dehydro-72 W.C. Wildman, J . Amer. Chem. SOL, 1958, 80, 2567.73 E. W. Warnhoff and W. C. Wildman, Chem. and Ind., 1958, 1293.74 V. Boekelheide and G. C . Morrison, J . Amer. Chem. SOL, 1958, 80, 3905.75 L. Marion, X V I t h Internat. Congr. Pure Appl. Chem. ; Experientia, Suppl. VII,76 D. Dvornik and 0. E. Edwards. Chem. and Ind., 1958, 623.1957, 328; K. Wiesner and 2. Valenta, Fortschr. Chem. org. Naturstoffe, 1958, 16, 26SAXTON : ALKALOIDS. 313genation product of ati~ine.~’ The synthesis of compound (35) constitutesthe first unequivocal evidence relating the nitrogen atom to the remainderof the molecule.The alternative location of the ally1 alcohol system(positions lS,19) is excluded by the observation that reduction of related( 3 ‘ )Me0 * 0(33) (34)ketones by sodium borohydride yields a mixture of epimeric alcohols;since position 19 is hindered, reduction of a 19-ketone would be expected toyield only one of the epimeric 19-alcohols.76~ 77 Ajaconine has been identifiedas 9-hydroxyatisine, the 9-hydroxyl group being cis to the heterocyclicbridge and equatorial; this work also determines the position of the carbonylgroup in atidine, and is of particular interest in connection with the proposedbiosynthesis of lycoct~nine.~~Napellonine is now known to be identical with songorine, and this hasresulted in the correction of some anomalies in their ~hemistry.7~ Sincedehydrogenation gives 7-ethyl-1,lO-dimethylphenanthrene and 7-ethyl-l-methy1-3-azaphenanthreneJ and since songorine contains an N-ethyl group,the structure proposed earlierso must be replaced by one containing a10,17-bond, as in (36).79In two independent investigations the relation previously suspectedbetween lycoctonine (37; R = R” = R”’ = Me, R’ = H) and delpheline(38; R = H) has been confirmed.The more direct method involvedmethylation of delpheline with sodium hydride and methyl iodide to givethe ether (38; R = Me), which, on acid hydrolysis, afforded deoxylycoc-tonine.sl In the second approach, demethoxylation of anhydrodeoxyly-coctonam, followed by oxidation with selenium dioxide, gave the diketo-lactam (39), which, as expected, was identical with dehydrodemethylene-77 S.W. Pelletier, Chern. and Ind., 1958, 1116; D. M. Locke and S. W. Pelletier,78 D. Dvornik and 0. E. Edwards, PYOC. Chem. SOC., 1958, 280.79 K. Wiesner, S. Ito, and 2. Valenta, Experientia, 1958, 15, 167.J . Amer. Chem. SOC., 1958, 80, 2588.Ann. Reports, 1957, 54, 261.M. Carmack, J. P. Ferris, J. Harvey, P. L. Magat, E. W. Martin, and D. W. Mayo,J . Amer. Chenz. SOC., 1958, 80, 497314 ORGANIC CHEMISTRY.oxodelpheline pinacone.S2 Deltaline, a new alkaloid from Delphiniumbarbeyi and D. occidentale, has structure (38; R = Ac), with an additionalhydroxyl group; reaction with thionyl chloride, followed by reduction withlithium aluminium hydride, converts it into delpheline.81The structure (37; R = R’ = Me, R” = R”‘ = H) proposed earlier fordelcosine 83 has now been shown to be untenable, since oxidation of oxo-delcosine , the lactam corresponding to delcosine, gives didehydro-oxo-delcosine, which is a diketone containing keto-groups in 5- and 6-memberedrings.Accordingly, delcosine is now formulated as (37; R = R”‘ = H,R’ = R” = Me), and this has been verified by preferential methylation ofthe hydroxyl group in the 5-membered ring, which yields delsoline (37;R = H, R = R” = R”’ = Me).M In these formulgtions for delcosine anddelsoline the stereochemistry is not proved; however, the formation of acarbinolamine ether on permanganate oxidation of delsoline suggests thatthe hydroxyl group in ring A is cis with respect to the nitrogen bridge, i.e.,opposite to the configuration of the corresponding methoxyl group inlycoc tonine .85Miscellaneous.-The chemical evidence relating to the structure ofannotinine has been discussed in details6Further work on the synthesis of muscarine and its stereoisomers hasbeen des~ribed,~~,~* including a new synthesis of (j-)-mu~carine.~~ Twogroups have recorded the resolution of (j-)-muscarine by means of di-p-toluoyltartaric acid, and the isolation of pure (+ )-muscarine, identical withnatural muscarine .88HOMeOR”‘37)CH 2* OR‘H- 0 M e.OMeCO2HICH2ICHHOIC’ ‘CH382 0.E. Edwards, L.Marion, and K. H. Palmer, Canad. J . Chem., 1958, 36, 1097.83 R. Anet, D. W. Clayton, and L. Marion, ibid., 1957, 35, 397; R. Anet and L.84 V. Skaric and L. Marion, J . Amer. Chem. SOC., 1958, 80, 4434.S5 F. Sparatore, R. Greenhalgh, and L. Marion, Tetrahedron, 1958, 4, 157.88 K. Wiesner, 2. Valenta, W. A. Ayer, L. R. Fowler, and J. E. Francis, ibid., p. 87.87 C. H. Eugster, F. Hafliger, R. Denss, and E. Girod, Helv. Chim. A d a , 1958, 41,205, 583, 705.88 Idem, ibid., p. 886; H. C. Cox, E. Hardegger, F. Kogl, P. Liechti, F. Lohse, andC. A. Salemink, ibid., p. 229.a9 T. Matsumoto and H. Maekawa, A?zgcw. Chem., 1958, 70, 507.Marion, ibid., 1958, 36, 766OVEREND: CARBOHYDRATES. 315Chaksine, a monoterpene alkaloid of Cassia absus L., is unusual in thatit contains a guanidine system in the molecule.An important product ofalkali fusion is the tricarboxylic acid (40), which is accompanied by Z-methyl-pimelic acid; the latter can also be obtained by oxidation of chaksine.These properties are best explained by the constitution (41) for c h a k ~ i n e . ~ ~J. E. S.11. CARBOHYDRATESIN last year's Report there was no reference to polysaccharide chemistry.This was not the result of a slackening of interest, and in fact the majority ofchemists who work with carbohydrates are concerned with this aspect ofthe subject. In this Report the emphasis is on oligo- and poly-saccharidesand some of the developments during the past two years will be described.Consideration of the enzymology of polysaccharides is omitted although it isappreciated that important evidence concerning polysaccharide structure isobtained frequently by this approach to the problem.Polysaccharides-An extensive review of cereal carbohydrates has beenpub1ished.lMethods for the fractionation of polysaccharides and detection of theircomponents continue to attract attention.The precipitation of neutralpolysaccharides by cationic detergents,2 the use of barium hydroxide as aselective precipitant for hemicelluloses,3 and the fractionation of alginateswith manganous and ferrous salts4 have been examined and found to beuseful methods for separating polysaccharides. The selective precipitationwith " Cetavlon " (cetyltrimethylammonium bromide) of neutral poly-saccharides which form borate complexes has been s t ~ d i e d .~ Phosphateprecipitation is useful for the isolation of a clinical dextran fraction;fractionation is achieved and schemes can be devised for the separation ofmany neutral polysaccharides. Some advantages accrue if ultrafiltrationis used for fractionation.' The fractionation of potato starch by centrifug-ation in alkali * and the separation of amylose from amylopectin by anextraction-sedimentation procedure have been discussed. Investigationsof the differential thermal analysis lo and electrophoresis on columns l1 andon paper l2 of saccharides have had useful results. While it is possible toseparate polysaccharides which have entirely different structures byO0 K. Wiesner, 2. Valenta, B.S. Hurlbert, F. Bickelhaupt, and L. R. Fowler, J .Amer. Chem. Soc., 1958, 80, 1521; G. Singh, G. V. Nair, K. P. Aggarwal, and S. S.Saksena, J . Sci. Ind. Res., India, 1958, 17, B, 332.I. A. Preece, Roy. Inst. Chem. Lectures, Monographs, and Reports, 1967, No. 2.H. Palmstierna, J. E. Scott, and S. Gardell, Acla Chem. Scand., 1957, 11, 1792.H. Meier, ibid., 1958, 12, 144.R. H. McDowell, Chem. and Ind., 1958, 1401.S . A. Barker, M. Stacey, and G. Zweifel, ibid., 1957, 330.L. Lacko, J. M%lek, and J . DvorAkovA, ibid., 1958, 1553; see also Coll. Czech. Chem.' K. C. B. Wilkie, J. K. N. Jones, B. J. Excell, and R. E. Semple, Canad. J . Chem.,* H. Baum and G. A. Gilbert, J . Colloid Sci., 1956, 11, 428.lo H. Morita, Analyt. Chem., 1957, 29, 1095.l2 E.Eurcik and W. Beutmann, Naturwiss., 1957, 44, 42.Comm., 1958, 23, 361.1957, 35, 795.E. M. Montgomery and F. R. Senti, J . Polymer Sci., 1958, 28, 1.B. J. Hocevar and D. H. Northcote, Nature, 1957, 179, 488316 ORGANIC CHEMISTRY.electrophoresis in a borate buffer,13 the inhomogeneity of a single poly-saccharide cannot be ascertained in this way. Replacement of the boratewith S~-sodium hydroxide gives some improvement and by its use it hasbeen shown that many polysaccharides hitherto assumed to be essentiallyhomogeneous can be separated into two or more components.14 Forexample, a range of amylopectins was found, not only to be hetero-geneous, but also to differ from each other. Glycogens were composed of twofractions and laminarin (from L.digitata and L. cloustoni) was heterogeneous,as was a wide range of gums. Heterogeneity was found in hemicellulosesfrom maize hulls, wheat and flax straw, and ramie grass : the so-called hemi-celluloses from aspen wood, slash pine, loblolly pine, and western hemlockwere heterogeneous. The crystalline xylans produced from beech wood andbarley straw, and the galactomannan of sugar-beet pulp were homogeneous.Fructans from rye flour, perennial rye grass, and dahlia were homogeneousbut the fructans from the ti root and from cocksfoot contained two com-ponents. Carrageenin l5 and agar l6 were mixtures. Heparin, hyaluronicacid, and chondroitin sulphate behaved individually as homogeneouspolymers but were easily separated from each other. The method appearsto be extremely useful for the examination of polysaccharide preparations.A spectrophotometric determination of total carbohydrate l7 and acolorimetric method for the determination of linkage in hexosamine-containing compounds l8 have been described.The carbazole reaction hasbeen adapted for the estimation of glucuronolactone, glucose, and xylose insolutions containing any or all of these compounds in the concentrationrange 10-100 pg./ml. The method has been used successfully with someacidic poly~accharides.~~ An infrared spectrophotometric procedure for theanalysis of cellulose and modified cellulose,2° an infrared microtechnique forthe identification of carbohydrates,21 and the differentiation of y- and6-aldonolactones 22 (in y-lactones carbonyl absorption occurs at 1765-1790 crn.-l, whereas in 8-lactones it is at 1726-1760 cm.-l> have been reported.A new chemical method for the determination of molecular weights ofcertain polysa~charides,~~ a procedure for mi~ro-methylation,~~ and a micro-method for the estimation of cellulose 25 are of interest.The natural occurrence of several new sugars has been recognised.2-O-Methyl-~-fucose has been identified in plum-leaf polysaccharides.26 Thel3 K.W. Fuller and D. H. Northcote, Biochem. J . , 1956, 64, 657.l4 B. A. Lewis and F. Smith, J . Amer. Chem. Soc., 1957, 79, 3929.l5 Cf. D. B. Smith and W. H. Cook, Arch. Biochem. Biophys., 1953, 45, 232.l6 Cf. C. Araki and K. Arai, Bull. Chem. Soc. Japan, 1956, 29, 543.la J.A. Cifonelli and A. Dorfman, J . Biol. Chem., 1958, 231, 11.lo J. M. Bowness, Biochem. J., 1957, 67, 295.2o R. T. O'Connor, E. F. Du PrB, and E. R. McCall, Analyt. Chem., 1957, 29, 998.21 F. E. Resnik, L. S. Harrow, J. C. Holmes, M. E. Bill, and F. L. Greene, ibid.,22 S. A. Barker, E. J. Bourne, R. M. Pinkard, and D. H. Whiffen, Chem. and Ind.,23 A. M. Unrau and F. Smith, ibid., 1957, 330.24 H. S. Isbell, H. L. Frush, B. H. Bruckner, G. N. Kowkabany, and G. Wampler,25 G. G. Dearing, Nature, 1957, 179, 579.26 J. D. Anderson, P. Andrews, and L. Hough, Chem. and Ind., 1957, 1453.B. R. Hewitt, Nature, 1958, 182, 246.p. 1874.1958, 658.Analyt. Chem., 1957, 29, 1523OVEREND: CARBOHYDRATES. 317position of the O-methyl group is of biogenetic interest since other naturallyoccurring deoxy-0-methyl sugars carry the methoxyl substituent a tposition 3 (see Andrews and Hough 27 for experiments on the biosynthesis ofplum-leaf polysaccharides) .An aldoheptose, possibly D-glycero-L-manno-heptose, occurs in lipopolysaccharides of Haemophilus bronchsepticus,H. pertussis, and*H. parapertussis.28 It seems probable that, as in othermembers of the Pasteurella group, aldoheptoses are of general occurrence inlipopolysaccharides from strains of P. sejbti~a.~~ It is confirmed that L-guluronic acid residues exist in alginic acid.30There are several reports of the formation of polysaccharides by poly-condensation of glucose. The polymerisation of D-glucose by hydrogen ionsin dimethyl sulphoxide has been examined.31 Non-crystalline polymers areformed when m-D-glucose is heated in the presence of metaboric acid.32 Theproduct is heterogeneous as to both size and bond structuqe. In the highlybranched polyoses 1,4- and 1,6-linkages predominate.No information isavailable about the precise stereochemistry of these bonds but probably thereis a fairly high ratio of cc- to p-links. The polycondensation of a-D-glucose a t140-170" in a vacuum and in the presence of 0.164% phosphorous acid hasbeen studied.33 Addition of tetrahydrothiophen dioxide prevented formationof insoluble gels in melt polymerisations. Raising the polymerisation tem-perature increases the degree of branching in the polymers, and the fractionsof higher molecular weight also have a higher degree of branching.=The enormous output of research on cellulose chemistry continuesunabated and a wide range of derivatives of the polysaccharide is beinginvestigated. 3-Oxoglucose units exist in oxidised cellulose.% An assess-ment has been made of the reactivity of cellulose in a~etylation,3~ and thepreparation and properties are described of acetates, modified acetates,37and mixed esters.38 A mechanism of interaction of trifluoroacetic acidwith cellulose is outlined.39 Preparation of xanthate esters 4O and nitration,4127 P.Andrews and L. Hough, Biochem. J., 1957, 67, 1 1 ~ .28 A. P. Maclennan, ibid., p. 3 ~ .29 A. P. Maclennan and C. J. M. Rondle, Nature, 1957,180, 1045; cf. D. A. L. Davies,ibid., p. 1129.30 D. W. Drummond, E.L. Hirst, and E. Percival, Chem. and Ind., 1958, 1088;cf. F. G. Fischer and H. Dorfel, Z. physiol. Chem., 1955, 302, 186.31 I;. Micheel and W. Gresser, Chem. Bey., 1958, 91, 1214.32 H. W. Durand, 31. F. Dull, and R. S. Tipson, J . Amer. Chem. Soc., 1958, 80, 3691.33 P. T. Mora and J. W. Wood, ibid., p. 685.34 P. T. Mora, J. W. Wood, P. Maury, and B. G. Young, ibid., p. 693.35 B. Lindberg and 0. Theander, Acta Chem. Scand., 1957, 11, 1355.38 C. J. Malm, K. T. Barkey, J. T. Schmitt, and D. C. May, Ind. Eng. Chem., 1957,49, 763; see also C. J. Malm, L. J. Tanghe, H. M. Herzog, and M. H. Stewart, ibid.,1958, 50, 1061.37 C. J. hfalni, K. T. Barkey, M. Salo, and D. C. May, ibid., 1957, 49, 79; F. A. H.Rice and A. R. Johnson, J . Amer. Chem. SOC., 1957, 79, 5049; J.F. Haskins and G. G.Sundenvirth, ibid., p. 1492.s* W. Voss and H. Reimschussel, Makromol. Chem., 1958, 28, 110.39 A. L. Geddes, J . Polymer Sci., 1956, 22, 31.*O E. G. Adamek and C. B. Purves, Canad. J . Chem., 1957, 35, 960; 2. Rybicki,Przemysl Chem., 1957, 13, 18.*1 T. Urbanski and A. Siemaszko, Bull. Acad. polon. Sci., C1. 111, 1957, 5, 1145;S. Watanabe, J . Chem. SOC. Japan, I n d . Chem. Sect., 1958, 61, 370, 374; T. S. A. Pad-manabham, S. K. Ranganathan, T. N. Rawal, and L. R. Sud, J . Sci. I n d . Res., India,1957, 16, B, 414318 ORGANIC CHEMISTRY.and the location of substituents in the products ( x a n t h a t e ~ , ~ ~ nitrates 43),continue to occupy chemists.c yanomet h yl ,45 carbox yme t h ydrox ye t h yl ,47 hydroxypropyl,48 a-hydr-~xyphenethyl,~~ thi~urethane,~~ ~ h t h a l a t e , ~ ~ methane~ulphonyl,~~ and chloro-compounds.53 The thermal decomposition of cellulose 54 and its acetate 55has been investigated. a-Hydroxy-nitriles have been recognised among thereduced-pressure ignition products of cellulose nitrate.5s The absence ofother non-gaseous nitrogenous substances was demonstrated.By theignition of [14C]cellulose nitrate, labelled at positions 1 and 6 of the anhydro-glucose units, it was demonstrated that C(0 gives mainly carbon dioxide andsmaller amounts of formic acid and glyoxal (from C(l) and C(d), and C(s) givespredominantly formaldehyde with smaller amounts of formic acid andcarbon dioxide.67Attempts a r t being made to determine how the two components ofstarch are incorporated into the granule and how the physical nature of thegranule governs the efficiency and ease of fractionation.Water preferentiallyleaches short-chain linear material from potato-starch granules.58 Itsaction is both inefficient and incomplete in comparison with conventionalmethods involving complete disruption of the granular structure. Theimportance of oxygen-free conditions to prevent amylose degradationin the fractionation of potato starch has been empha~ised.~~ A criticalexamination has been undertaken of the behaviour of oat and wheatstarch on fractionation by dispersion and aqueous leaching.60 The granularstarch in sweet corn (Zea mays) is a typical cereal starchs1 whose pro-perties are unaltered by the coexistence in the grain of water-solubleOther derivatives studied include4a E.P. Swan and C. B. Purves, Canad. J . Chem., 1957, 35, 1522; A. K. Sanyal,E. L. Falconer, D. L. Vincent, and C. B. Purves, ibid., p. 1164; J. K. Miller and J. D.Geerdes, Abs. Amer. Chem. SOC. Meeting, Miami, 1957, 3 ~ .43 E. L. Falconer and C. B. Purves, J . Amer. Chem. SOC., 1957, 79, 5308.44 V. Derevitskaya, M. Prokof’yeva, and 2. Rogovin, Zhur. obshchei Khim., 1958,28, 716; I. Croon, B. Lindberg, and A. Ros, Svensk Papperstidn., 1958, 61, 35.46 N. M. Bikales, A. H. Gruber, and A. L. Rapoport, Abs. Amer. Chem. SOC. Meeting,Miami, 1957, 1 ~ .4~ D. K. Basu and P. K. Choudhury, 7. Indian Chem. Soc., 1958, 35, 173; C.Simionescu and N. Asandei, Chim.analyt., 1958, 40, 204.47 H. H. Brownell and C. B. Purves, Canad. J . Chem., 1957, 35, 677.48 G. Froment, Ind. chim. belge, 1958, 23, 3.48 G. Montegudet, Compt. rend., 1957, 244, 2178.50 A. L. Allewelt and W. R. Watt, Ind. Eng. Chem., 1957, 49, 68.51 C. J. Malm, J. W. Mench, B. Fulkerson, and G. D. Hiatt, ibid., p. 84.52 R. W. Roberts, J . Amer. Chem. Soc., 1957, 79, 1175.53 R. L. Boehm, J . Org. Chem., 1958, 23, 1716.54 A. Pacault and G. Sauret, Compt. rend., 1958, 248, 608; 0. P. Golova and R. G.Krylova, Doklady Akad. Nauk S.S.S.R., 1957, 116,419; 0. P. Golova, A. M. Pakhomov,Ye. A. Andriyevskaya, and R. G. Krylova, ibid., 1957, 115, 1122; 0. P. Golova, A. M.Pakhomov, and Ye. A. Andriyevskaya, Izvest. Akad. Nauk S.S.S.R., Otdel. khim. Nauk,1957, 1499.55 H.Maeda, K. Saito, and T. Kawai, J . Chem. SOC. Japan, Ind. Chem. Sect., 1958,61, 605.56 M. L. Wolfrom, A. Chaney, and P. McWain, J . Amer. Chem. Soc., 1958, 80, 946.57 F. Shafizadeh and M. L. Wolfrom, ibid., p. 1675.58 J. M. G. Cowie and C. T. Greenwood, J., 1957, 2862.59 Idem, J., 1957, 4640; see also G. A. Gilbert, Starke, 1958, 10, 95.6o -4. W. Arbuckle and C. T. Greenwood, J., 1958, 2626.C . T. Greenwood and P. C. Das Gupta, J., 1958, 707OVEREND : CARBOHYDRATES. 310glucosans.62 Apparently acid-treatment preferentially affects the amorphousrather than the crystalline region of the potato-starch granule.63 Althoughboth the amylose and the amylopectin component were degraded, the latterwas broken down preferentially.Similar results were obtained with wheat-starch granules64 but the rate of degradation was less than for potato,probably owing to the more compact structure of wheat starch. Radio-chemical evidence has been provided for heterogeneity in wheat starch.65A comprehensive linkage-analysis of floridean starch (from Dilsea e d d i s )has established that it contains a small proportion of 1,3-~-1inkages.~~ Thedegree of multiple branching in an amylopectin (or glycogen) can beevaluated from the chain lengths of the corresponding muscle-phosphorylaseand P-amylase limit d e x t r i n ~ . ~ ~ A range of glycogens showed small butsignificant differences in degree of multiple branching, and amylopectinsshowed a similar range of values. Accordingly the marked physicochemicaldifferences between glycogen and amylopectin cannot be related todifferences in the degree of multiple branching.The dextrinisation of maize 68 and wheat 69 starch is accompanied byconsiderable transglycosidation and the development of a highly .branchedstructure.The action of O.Fi~-sodium hydroxide at 100" on amylose is oftwo main types : I' degradation " producing mainly D -glucoisosaccharinic,formic, and lactic acid, and a " stopping " reaction affording alkali-stableamylose probably bearing terminal D-glucometasaccharinic acid units.70Glyoxylic and D-erythronic acids are the principal products from the hypo-chlorite oxidation of , maize-starch arnyl~pectin.~~ Optimum conditionshave been determined for the oxidation by chlorous acid of periodate-oxidised maize starch.72 The extent of formylation of starch is dependentupon the ratio of formic acid to starch and on the water content of thesystem.73 The preparation and properties of mixed esters of amylose havebeen outlined.74The molecular structure of glycogens has been re~iewed.~j A comparisonof the molecular weights of glycogens extracted from rabbit liver by' hotalkali and by cold trichloroacetic acid indicates that the latter methodyields material which approximates most closely to native gly~ogen.'~Ultracentrifugal analysis of 23 glycogens, isolated from various sources,showed that most of the samples were polydisperse : the molecular weightsand P.C. Das Gupta, J., 1958, 703.62 Cf. S. Peat, W. J. Whelan, and J .R. Turvey. J., 1956, 2317; C. T. Greenwood63 J. M. G. Cowie and C. T. Greenwood, J., 1957, 2658.64 A. W. Arbuckle and C. T. Greenwood, J., 1958, 2629.65 A. S. Perlin, Canad. J . Chem., 1958, 36, 810.66 S. Peat, J. R. Turvey, and J. M8n Evans, Nature, 1957, 179, 261.67 A. M. Liddle and D. J. Manners, Biochem. J.. 1955, 61, X I I ; J . , 1957, 4708.68 J. D. Geerdes, B. A. Lewis, and F. Smith, J . Amer. Chem. SOC., 1957, 79, 4209.6Q G. M. Christensen and F. Smith, ibid., p. 4492.70 G. Machell and G. N. Richards, J., 1958, 1199.72 B. T. Hofreiter, I. A. Wolff, and C. L. Mehltretter, ibid., p. 6457.73 I. A. Wolff, D. W. Olds, and G. E. Hilbert, ibid., p. 3860.74 Idem, I n d . Eng. Chem., 1957, 49, 1247.75 D. J. Manners, Adv. Carbohydrate Chem., 1957, 12, 262.76 W.A. J. Bryce, C. T. Greenwood, and I. G. Jones, J . , 1958, 3845; cf. C. T.R. L. Whistler and R. Schweiger, J . Amer. Chem. SOC., 1957, 79, 6460.Greenwood and D. J. Manners, Proc. Chem. SOC., 1957, 26320 ORGANIC CHEMISTRY.of the main components lie in the range 3-9 x lo6. It was concluded 77that it is difficult to avoid degradation during the extraction of glycogen.Further evidence from periodate oxidations confirms that the averagelength of chains in glycogens is normally about 12 glucose residues.78Investigations of the extraction and fracti~nation,~~ and the structure,B* ofbrain glycogen have been reported.The characterisation of dextrans by the optical rotation of theircuprammonium complexes,81 and the relation between specific opticalrotation and branching of dextrans,82 have been examined.Some phos-phoric esters of dextran have been synthe~ised.~~ Experiments with baker’syeast glucan indicate that it is a linear polymer of p-D-glucopyranose unitsin which 1,3- and 1,6-linkages are arranged at random or in sequences suchthat a group of at least three 1,6-linkages is flanked on either side by 1,3-linkages.84 The combined proportion of non-reducing end-groups and1,6-links is 1 per 10 glucose residue^.^^^^^ Warsi and Whelan86 havereinvestigated the structure of pachyman and have shown that it is a polymerof p-glucose containing only 1,3-linkages : Takeda 87 had previouslyerroneously concluded that 1 ,&linkages were present.Purified isolichenin and lichenin from Iceland moss (Cetraria islandica)have been characterised by methylation and periodate oxidationa8 It hasbeen confirmed that lichenin is a linear polymer of p-D-glUCOSe containingboth 1,3- and 1,4-linkages.Chanda et aE.88 consider the ratio of 1,3- to1,4-linkages to be 3 : 7, whereas Peat and his co-workers *9 calculate theratio to lie between 1 : 2 and 1 : 3 and suggest that the lichenin chain is arepeating sequence of p-cellotriose units joined through 1,3-bonds. Iso-lichenin consists solely of D-glucose residues united by cc-1,3- and or-1,4-linkages in the relative proportion 3 : 2. The molecule appears to be linearwith an average chain length of 42-44 glucose units.8*The linkagesin soluble and insoluble laminarin have been analysed by partial hydrolysisand it has been confirmedg0 that the principal bond is of the 1,3-type,between p-D-glucopyranose residues.In a hydrolysate of insolublelaminarin 14 mono-, di-, and tri-saccharide products were identified; 91 ofthese D-glucose, D-mannitol, laminaribiose, gentiobiose, l-O-p-glucosyl-mannitol, laminaritriose, 3-O-gentiobiosylglucose, 6-O-p-laminaribiosyl-glucose, and 1-O-p-laminaribiosylmannitol are considered to be trueImportant papers about laminarin have been published.77 W. A. J. Bryce, C. T. Greenwood, I. G. Jones, and D. J. Manners, J., 1958, 711.78 D. J. Manners and (in part) A. R. Archibald, ibid., 1957, 2205.7s B. I. Khaikina and L. S. Krachko, UKrain. biokhim. Zhur., 1957, 29, 10.so Ye. Ye. Gonchareva, Doklady Akad.Nauk S.S.S.R., 1957, 112, 899.81 T. A. Scott, N. N. Hellman, and F. R. Senti, J . Amer. Chem. SOC., 1957, 79, 1178.82 C. E. Rowe, Chem. and Ind., 1957, 816.83 A. Gallo and A. Vercellone, Chimica e Industria, 1957, 39, 1.84 S. Peat, W. J. Whelan, and T. E. Edwards, J., 1958, 3862.86 S. Peat, J. R. Turvey, and J. M. Evans, J., 1958, 3868.a8 S. A. Warsi and W. J. Whelan, Chem. and Ind., 1957, 1573.89 S. Peat, W. J. Whelan, and J. G. Roberts, J., 1957, 3916.90 S. Peat, W. J. Whelan, and H. G. Lawley, J., 1958, 724.91 Idem, J., 1958, 729.K. Takeda, Mem. Tottori agric. Coll., 1935, 3, 1.N. B. Chanda, E. L. Hirst, and D. J. Manners, J . , 1957, 1951OVEREND CARBOHYDRATES. 321structural fragments of laminarin. The presence of mannitol has beenreported by other workers Peat et aLgl suggest that the laminarinmolecules consist of unbranched chains of @-1,3-linked glucose units oc-casionally interrupted by p-1,6-linkages and that some but not all areterminated by mannitol.It is considered that soluble laminarin probablyhas a similar structure but contains a higher proportion of mannitol and off3-1,6-linkages (cf. Anderson et aLg2). Fig. 1 shows the suggested structureand the di- and tri-saccharides which would be produced by partialhydrolysis.6-0-/3-Larninaribiosyl- 1-O-p-Glucosyl-Laminaribiose Gentiobiose glucose mannitolt t t tJ- J.Laminaritriose 3-O-~-Gentiobiosylglucose 1 -0-P-Laminaribiosyl-mannitolKey: 0 = D-glucopyranose unit; M = mannitol.(N.B. Some of the molecules do not contain mannitol.)FIG.1Peat et uLg1 preferred to leave open the question of branching but Hirstand his colleagues 93 have evidence which supports a branched structure unlessthe 1,6-linkages occur exclusively near the end of the chains. Successiveperiodate oxidation and degradation with phenylhydrazine of laminarin gaveafter three oxidations and two degradations a residual oxopolysaccharide.Polysaccharides derived from timbers, grasses, and cereals continue toattract world-wide attention. Information concerning lignin-carbohydratebonding is discussed in several publication^.^^ Arabogalactans from thewoods of European larch (Larix d e c i d u ~ ) , ~ ~ white spruce [Picea glauca(Moench) VOSS],~~ and Jack pine (Pinus banksiana Lamb) 97 have beenstudied.The material from larch is highly branched: the framework of themolecule consists of chains of 1,3-linked P-D-galactopyranose units, themajority of which carry side chains containing an average of two 1,6-linkedp-D-galactopyranose residues. The majority of the arabinose occurs as 3-0-p-L-arabofuranosyl-L-arabofuranosyl side chains. The structural features ofspruce arabogalactan are generally similar. A unique structure cannot beformulated for Jack pine arabogalactan but it seems that a chain of92 A. M. Unrau and F. Smith, Chem. and Ind., 1957, 1178; F. B. Anderson, E. L.Hirst, and D. J. Manners, ibid., p . 1178; F. B. Anderson, E. L. Hirst, D. J. Manners,and A. G. ROSS, J., 1958, 3233.93 E. L. Hirst, J.J. O’Donnell, and E. Percival, Chem. and Ind., 1958, 834.94 B. 0. Lindgren, Svensk Papperstidn., 1958, 61, 669; R. Nelson and C. Schuerch,J . Polymer Sci., 1956, 22, 435; A. Hayashi and I. Tachi, J . Agric. Chem. SOC. Japan,1956, 30, 442, 791.95 G. 0. Aspinall, E. L. Hirst, and E. Ramstad, J., 1958, 593.s~ G. A. Adams, Caiiad. J . Chem., 1958, 36, 756.97 C. T. Bishop, ibid., 1957, 85, 1010.REP-VOL. LV 322 ORGANIC CHEMISTRY.1,6-linked D-galactopyranose units is terminated a t the non-reducing end byan unsubstituted D-galactopyranose or L-arabofuranose residue. Throughposition 3 of some of the galactose units other 1,6-linked chains of D-galacto-pyranose units are attached and some are terminated by L-arabofuranoseunits. At one point in the molecule branching occurs through positions 3and 4 instead of 3 and 6 of a D-galactopyranose residue.Most of theglycosidic linkages are of the P-configuration. When hydrolysed underconditions sufficiently mild to cleave almost exclusively only furanosidiclinkages an arabogalactan from Larix occidentalis yielded a mixture ofarabinose, galactose, 3-O-p-~-arabopyranosyl-~-arabinose, 6-O-P-~-galacto-pyranosyl-D-galactose, and a trisa~charide.~~ A glucomannan from westernred cedar (Thuja plicata Donn) (glucose : mannose = approx. 1 : 2.5) issimilar to glucomannans from other woods, being a short, predominantlystraight-chain polymer in which the units are linked by 1,4-p-glycosidicbonds. Graded hydrolysis afforded cellobiose, mannobiose, glucosido-mannose, mannosidoglucose, and a mannotrio~e.~~ Similar di- and tri-saccharides were obtained from a glucomannan from western hemlock(Tsuga heterophyZZa) .loo The glucomannan fraction of sitka spruce (Piceasitchensis) hemicellulose contains a t least two essentially linear components,a p-1,4-linked glucan and a p-1,4-linked glucomannan.lo1 Two gluco-mannans from Norwegian spruce (Picea abies) have been studied by themethylation and the periodate oxidation procedure : lo2 they have the samegeneral structure, being composed essentially of a-1,4-linked sugar residues ;each molecule has 3 4 branch points, which are attached to the 3-position ofglucose residues ; the non-reducing end-groups are principally mannoseresidues.Graded hydrolysis indicates that in loblolly pine (Pinus takda)glucose and mannose residues are linked by p-glycosidic bonds in a poly-saccharide (or group of polysaccharides) which is distinct and separablefrom the residual ‘‘ a-cellulose ” of the Pentosan and hexosanfractions of hemicelluloses from aspen wood (Populis tremuloides) have beenexamined.lo4 By conventional methods it has been demonstrated that thehemicellulose of the wood of white elm (Ulmus americana) contains 1851,4-linearly linked p-D-xylopyranose residues, every seventh of whichcarries a single terminal side chain of 4-O-methyl-~-glucuronic acid attachedby an a-glycosidic bond through C(g.lo5 In the hemicellulose of white birch(Betula papyrifera) there is a chain of a minimum of 110 and a maximum of190 p-1 ,&linked D-xylopyranose units.On the average, every eleventhanhydroxylose unit carries a t position 2 a single glycosidically bonded4-O-methyl-~-g~ucuronic acid residue.lo6 The water-soluble hemicellulose9s H. Bouveng and B. Lindberg, Actu Chem. Scand., 1956, 10, 1515.99 J. K. Hamilton and E. V. Partlow, J . Amer. Chem. SOC., 1958, 80, 4880.100 J. K. Hamilton and H. W. Kircher, ibid., p. 4703.101 G. 0. Aspinall, R. A. Laidlaw, and R. B. Rushbrook, J., 1957, 4444; cf. G. G. S.Dutton and K. Hunt, J . Amer. Chem. SOC., 1958, 80, 5697.102 I. Croon and B. Lindberg, Actu Chem. Scand., 1958, 12, 453.103 J. K. N. Jones and T. J. Painter, J., 1957, 669.104 J. K. N. Jones, E. Merler, and L. E. Wise, Canud. J . Chem., 1957, 35, 634.105 J .K. Gillham and T. E. Timell, ibid., 1958, 38, 1465; cf. ibid., p. 410.106 C. P. J. Glaudemans and T. E. Timell, J . Amer. Chem. SOC., 1958, 80, 1309; cf.J. K. Gillham and T. E. Timell, Svensk Pupperstidn., 1958, 81. 540OVEREND CARBOHYDRATES. 323from American beachwood (Fagas grandifolia) differs in some respects fromthat derived from the European variety.lo7 Forty-five p-D-xylopyranoseunits are 1,4-linked and there is a branch point at position 2 of a xylose unit.Five 4-O-methy~-~-g~ucuronic acid residues are joined as single terminal sidechains of the xylose units of the main structure by a-1,2-bonds. Theuronic acid distribution along the chain is unknown but the acids cannot beattached to the units forming the branch points or to the non-reducing end.A brief account of the hemicellulose of Japanese beachwood has appeared.lWEuropean larch (Larix decidua) hemicellulose fractions contain a xylancomprised of unbranched chains of about 100 1,4-linked p-D-xylopyranoseresidues with every fifth or sixth residue carrying a terminal 4-O-methyl-~-glucuronic acid residue linked through position 2, and a smaller proportionof xylose residues carrying, on position 3, side chains terminated by L-arabo-furanose units.log On the present evidence it is impossible to state whetherthe L-arabofuranose residues are attached directly to the backbone of xyloseresidues or whether 1,4-linked D-XylOSe units are interposed with thearabinose residues terminating a longer side chain. By analogy with otherxylans the former alternative is more probable.Examination of jutehemicellulose I by partial acid hydrolysis and methylation leads to thepartial structure (1) for the polysaccharide : approximately every seventhresidue carries a D-G~A group and the degree of branching in the xylosechain is small. Probably in the case of jute hemicellulose, as with otherxylans, a range is present of closely related molecular species of the samegeneral type which differ in their more detailed structures. Formula (2) isI1 I(1) D-G~A D-xylp(u-Xylp = D-xylopyranose ; D - G ~ A = 4-O-methyl-~-glucuronic acid.)A 4 I x-x-x-x-x-I(2) Afavoured for the highly branched barley araboxylan. Barley huskhemicellulose has also been studied and contains many of the structuralfeatures encountered in other xylans.l12 The highly branched araboxylanfrom rye flour is built up of 1,4-linked p-D-xylopyranose residues with ap-proximately every second xylose unit carrying a terminal L-arabofuranoselinked through position 3.113 The xylan chain in the araboxylan from maizecobs is extensively branched with L-arabinose units attached in short, linear107and R,108109110G.A. Adams, Canad. J . Chem., 1957, 35, 566; cf. G. 0. Aspinall, E. L. Hirst,, S. Mahomed, J., 1954, 1734.S. Machida, M. Inano, and Y. Matsumura, Bull. Chem. SOC. Japan, 1957, 30, 201.G. 0. Aspinall and J. E. McKay, J., 1958, 1059.G. 0. Aspinall and P. C. Das Gupta, J., 1958, 3627.111 G. 0. Aspinall and R. J. Ferrier, J., 1958, 638.112 Idem, J., 1957, 4188.113 G.0. Aspinall and R. J. Sturgeon, J., 1957, 4469324 ORGANIC CHEMISTRY.side chains.l14 The wood xylans which have been examined are all charac-terised by the presence of 4-O-methy~-~-g~ucuronic acid residues attached asside chains to D-xylose by 1,2-linkages. The proportions of uronic acidgroups are in general somewhat higher in the xylans from soft woods (15-20%) than in those of hard woods (8-15%). Some of these xylans alsocontain a small proportion of L-arabofuranose residues. In contrast, thexylans from cereals are in general characterised by a higher proportion ofarabinose groups and a lower proportion of uronic acid groups.Increasing attention is being given to the isolation, characterisation, andstructural investigation of polysaccharides derived from micro-organisms.Considering the difficulties involved in this work it is stimulating to note theprogress being made, only a fraction of which can be outlined here.Theglobulin, concanavalin-A,, has been used to ascertain whether certain bacterialglucans are related to glycogen or amyl~pectin.~~~ The glycogen ofEscherichia coli B has been fractionated into portions severally of high andlow molecular weight (molecular weights = 40-90 x lo6 and <2 x 106),116which have been related to the metabolism of the organism. A techniquehas been devised for labelling with 14C the glycogen of these cells withoutlabelling the protein to any appreciable extent.l17 The capsular poly-saccharide of Aerobacter aerogenes (N.C.T.C. 418) has a branched structurecontaining D-glucose and D-mannose residues with some of the formerpresent as non-reducing end-groups.The glucose residues are linkedmainly 1,4- but a few are 1,3-linked. Non-reducing end-groups (ca. 1 in 40)of glucuronic acid are a-1,4-linked to D-mannose residues which in turn arelinked to the remaining sugar units through the 3-po~ition.l~~ The linkageof the remaining mannose residues in the repeating unit has still to bedetermined. An acidic polysaccharide elaborated by A erobacter aerogeneson hydrolysis gives rhamnose, glucose, mannose, glucuronic acid, andaldobiuronic acids in which the major component is glucuronosylmannose.~~~Galactose, N-acetylglucosamine, and N-acetylgalactosamine (molar ratio2 : 1 : 1) are the components of a polysaccharide extractable fromB.s~btiZis.~~O Pneumococcus-specific polysaccharides have been examined.The type VIII material is a linear polymer of high molecular weight inwhich the repeating unit is -0-P-D-glucopyranosyluronic acid-( 1 --+ 4)-O-p-D-glucopyranosyl-( 1 __+ 4)-O-~-~-glucopyranosyl-( 1 _+ 4)-0 - a-D-galacto -pyranosyl-( 1 + 4)-.121 Recent immunochemical studies 122 indicated thattype XIV polysaccharide contained non-reducing end-groups of D-galactosetogether with D-galactose residues linked P-1,3- or P-l,S-, or involved inp-1,3,6-branch points. These conclusions have been examined by a chemical114 R. L. Whistler and G. E. Lauterbach, J . Amer. Chem. SOL, 1958, 80, 1987.115 J. A. Cifonelli and F.Smith, ibid., 1957, 79, 5055.116 T. Holme, T. Laurent, and H. Palmstierna, Acia Chem. Scand., 1958, 12, 1559.117 T. Holme and H. Palmstierna, ;bid., 1956, 10, 1557.118 S. A. Barker, A. B. Foster, I. R. Siddiqui, and M. Stacey, J., 1958, 2358.119 S. A. Barker, A. B. Foster, S. J. Pirt, I. R. Siddiqui, and M. Stacey, Nature,120 N. Sharon, ibid., 1957, 179, 919.121 J. K. N. Jones and M. B. Perry, J . Amer. Chem. SOC., 1957, 79, 2787.122 M. Heidelberger, S. A. Barker, and B. Bjorklund, ibid., 1958, 80, 113; P. A.Rebers, S . A. Barker, M. Heidelberger, 2. Dische, and E. E. Evans, ibid., p. 1135.1958,181, 999OVEREND : CARBOHYDRATES. 326method.123 Mannans from C. diphtheriae 124 and B. polymyxa 1% have beenstudied. The predominant glycosidic linkage in the branched poly-fructoside produced from sucrose by a Corynebacterium sp.is of the p-2,6-type.126 A lipopolysaccharide from Salmonella paratyehi A containedglucose, galactose, mannose, rhamnose, and a new 3,6-dideoxyaldohexose,for which the name " paratose " has been suggested.127 This compound isidentical with synthetic 3,6-dideoxy-~-ribo-hexose.~~~~Di-, Tri-, and Oligo-saccharides-The widespread use of graded hydrolysisfor the examination of polysaccharides has focused attention on methodsfor the isolation, characterisation, and synthesis of di-, tri-, and oligo-saccharides. Aspects of this subject have been reviewed.128 A semimicro-procedure for the investigation of oligosaccharides has been reported.lZ9Details are available for a preparative method of isolation of isomaltoseand gentiobiose from an acid-reversion mixture of D-glUCOSe.130 Koj ibiose 131and laminaribiose 132 have been isolated from hydrol." Graded acid-hydrolysis of chitosan followed by N-acetylation yields a polymer-homologous series of which the first 7 members have been isolated and~haracterised.l3~ Trehalose has been extracted from Porrocaeccuum decipienslarvae,134 and am-trehalose was isolated from the blood of Antheraeapolyphemzts 135 and was identified as a major blood sugar of insects.It hasbeen shown 136 that 4-0- and not 3-O-methyl-~-glucuronic acid (as claimedby Das Gupta and Sarkar 137) is a component of an aldobiuronic acid fromjute fibre hemicellulose. Montreuil 138 has isolated from human milk13 sugars other than lactose, all of which contain galactose and glucose,and most of them fucose and acetylglucosamine also.There seems littledoubt that these compounds are in many cases identical with a series of sub-stances obtained by Malpress and Hytten 139 from human milk by different123 S. A. Barker, M. Heidelberger, M. Stacey, and D. J. Tipper, J., 1958, 3468.124 0. K. Orlova and Ye. P. Yefimtseva, Biokhimiya, 1956, 21, 505.125 D. Murphy, C. T. Bishop, and G. A. Adams, Canad. J . Biochem. Physiol., 1956,126 G. Avigad and D. S. Feingold, Arch. Biochem. Biofihys., 1957, 70, 178.127 (a) D. A. L. Davies, A. M. Staub, I. Fromme, 0. Luderitz, and 0. Westphal,Nature, 1958, 181, 822; (b) C. Souquey, J. Tolonsky, E. Lederer, 0. Westphal, and 0.Liideritz, ibid., 1958, 182, 944.128 M.G. Blair and W. Pigman, Angew. Chem., 1957, 69, 422; M. Stacey, Bio-khimiya, 1957, 22, 241; R. Kuhn, Bull. Soc. Chim. biol., 1958, 40, 297; Angew. Chern.,1957, 69, 23.129 L. Hough, B. M. Woods, and M. B. Perry, Chem. and Ind., 1957, 1100.130 M. L. Wolfrom, A. Thompson, and A. M. Brownstein, J . Amer. Chem. SOC.,131 A. Sat0 and K. Aso, Nature, 1957, 180, 984.132 A. Sato, K. Watanabe, and K. Aso, Chem. and Ind., 1958, 887.133 S. A. Barker, A. B. Foster, M. Stacey, and J. M. Webber, J., 1958, 2218; Chem.and Ind., 1957, 208; cf. S. T. Horowitz, S. Roseman, and H. J. Blumenthal, J . Amey.Chem. Soc., 1957, 79, 5046.34, 1271.1958, 80, 2015.134 D. Fairbairn, Nature, 1958, 181, 1593.135 G. R. Wyatt and G.F. Kalf, J . Gen. Physiol., 1957, 40, 833.1313 H. C. Srivastava and G. A. Adams, Chem. and Ind., 1958, 920.137 P. C. Das Gupta and B. P. Sarkar, Textile Res. J., 1954, 24, 1071.138 J. Montreuil, Bull. SOC. Chim. biol., 1957, 39, 395.139 F. H. Malpress and F. E. Hytten, Nature, 1957, 180, 1201; Biochem. J., 1958,* Hydro1 is the mother liquor obtained after the separation of glucose froni an acid68, 708.hydrolysate of sweet-potato starch326 ORGANIC CHEMISTRY.fractionation procedures. Lactodifucotetraose and lacto-N-fucopentaoseI1 from human milk have been assigned structures (3) 140 and (4) 141 re-spectively.Enzymic syntheses have been described of 3-0- and 6-0-P-~-galacto-pyranosyl-D-glu~ose,~~~ 6-0-~-~-ga~actopyranosy~-~-ga~actose,~~~ 2-0-a-D-CH-0-C-H I 1 I I f 3HO+H IIIH-C-OHH-C-OHO--THCH,(3)CH,-OHU /7H HO-C-H I H-7-oHH-t-oHO-THICH-OH II H-C-OHB0BH-C- 0CH,-OH I(4) CH3140 R.Kuhn and A. Gauhe, AIznaZen, 1958, 611, 249.1 4 1 R. Kuhn, H. H. Baer, and A. Gauhe, Chem. Bey., 1958, 91, 364.142 J. H. Pazur, C . L. Tipton, T. Budovich, and J. M. Marsh, J . Amer. Chem. SOC.,1958, 80, 119OVEREND CARBOHYDKATES. 327glucopyranosyl-D-glucose (koj ibiose) ,143 O-p-D-gluco(and galacto) pyranosyl-(1 -+ 4)-O-[a-~-glucopyranosyl-( 1 __t 2)]-D-glUCOSe,1u a-lactosyl-p-fructo-furanoside,145 O-a-D-glucopyranosyl-( 1 + 6)-O-a-~-glucopyranosyl-( 1 +2) -p-~-fructofuranoside,~~~ and 3-O-~-~-glucopyranosyl-~-xylose.~~~ Anenzyme from S. fragdis disproportionates 6-O-~-~-galactopyranosy~-D-g~ucoseto glucose, galactose, and O-p-D-galactopyranosyl-( 1 _+ 6)-p-~-galacto-pyranosyl-(1 + 6)-~-glucose.~~~ With acetate as its.sole carbon sourceA . rtiger " 152 " produces mannitol, arabinitol, erythritol, glycerol, maltose,and cca-trehalose e~tracellularly.~~~ Fructose and cello-biose, -triose, and-tetraose, together with oligosaccharides which are not cellodextrins, wereformed when Acetobacter acetigenwn was grown on a defined medium contain-ing glucose.150 A homologous series of oligosaccharides produced byB. arabinosaceous (Birmingham) in a medium containing sucrose and 3-0-methyl-D-glucose is formed by successive addition of glucosyl units ina-1,6-linkage to 3-O-methyl-~-glucose.~~~Chemicalsyntheses have been outlined of 5-0-~-~-xylopyranosyl-~-arabinose,~~~ 2-0-p-D-xylopyranosyl-L-arabinose,l% 5-O-~-D-ga~actopyranosyl-~-arabinose,~~~ 6-0- ~-D-xylopyranosyl-~-gdact ose 3-0- p-D-galact opyranosyl-~-gdactose,1563-O-a-~-glucopyranosyl-~-glucose,~~~ 6-0-~-D-glu~osylmaltose,~~~ methyl[methyl - (4 - 0 - methyl - cc - D - galactopyranosyluronate)] - a - D - galacto-pyranosid~ronate~l59 and l-glyceritol-D-galactopyranosides.160Completion of the unequivocal proof by methylation of the structures ofisomaltose and gentiobiose is reported.130 A direct chemical proof has beenfurnished for the occurrence of the sucrose linkage in raffinose andstachyose.161 Establishment of the configuration a t the anomeric centre ofthe fructose moiety of sucrose completes the proof of its structure by purelychemical means.162 These results, together with previous X-ray evidence,permit the conclusion that the isorotation rules do correlate configurationwith rotation in the case of fructofuranosides. It is likely that the samesituation will apply to other ketofuranosides. The configuration ofA simplified synthesis of oligosaccharides has been rep0rted.15~143 K.Aso, K. Shibasaki, and M. Nakamura, Nature, 1958, 182, 1303.144 R. W. Bailey, S. A. Barker, E. J. Bourne, P. M. Grant, and M. Stacey, J., 1958,145 G. Avigad, J . Biol. Chem., 1957, 229, 121.146 S. A. Barker, E. J. Bourne, and 0. Theander, J., 1957, 2064.147 S. A. Barker, E. J. Bourne, G. C. Hewitt, and M. Stacey, J., 1957, 3541.148 J. H. Pazur, J. M.Marsh, and C. L. Tipton, J . Amer. Chem. SOC., 1958, 80,149 S. A. Barker, A. G6mez-SAnchez, and M. Stacey, J., 1958, 2583.150 T. K. Walker and H. B. Wright, Arch. Biochem. Biofihys., 1957, 69, 362.151 S. A. Barker, E. J. Bourne, P. M. Grant, and M. Stacey, J., 1958, 601.152 H. Bredereck, A. Wagner, and G. Faber, Angew. Chem., 1957, 69, 438.153 D. H. Ball and J, K. N. Jones, J., 1957, 4871.154 G. 0. Aspinall and R. J. Ferrier, J., 1958, 1501; Chem. and Ind., 1957, 819.155 I. J. Goldstein, F. Smith, and H. C. Srivastava, J . Amer. Chem. SOC., 1957,79,3858.158 D. H. Ball and J. K. N. Jones, J., 1958, 905.157 S. Haq and W. J. Whelan, J., 1958, 1342.158 A. Klemer, Angew. Chem., 1957, 69, 638.159 M. Gee, F. T. Jones, and R. M. McCready, J .Org. Chem., 1958, 23, 620.160 B. Wickberg, Acta Chem. Scand., 1958, 12, 1187.161 A. K. Mitra and A. S. Perlin, Canad. J . Chem., 1957, 35, 1079.16% R. U. Lemieux and J. P. Barrette, J . Amer. Chem. SOC., 1958, 80, 2243.1895.1433328 ORGANIC CHEMISTRY.glycosidic linkages in several reducing di- and tri-saccharides has beendetermined by the conversion of each substance into the corresponding2-O-glycosylglycerol, the configuration of which was readily e~tab1ished.l~~Compounds so examined include 3-O-~-~-galactopyranosyl-~-galactose, 3-0-a-D-galactopyranosyl-L-arabinose, 3-O-P-~-arabopyranosyl-~-arabinose, 2-0-p-D-xylopyranosyl-L-arabinose, 3-O-~-~-xylopyranosyl-~-arabinose, and4-O-~-~-xylopyranosyl-~-xylose, all partial hydrolysis products of poly-saccharides. Likewise the configuration in O-a-D-mannopyranosyl-( 1 +2)-O-~t-~-mannopyranosyl-( 1 + 2)-D-mannOSe was established.lM 2-033-D-Xylopyranosyl-L-arabinose (which originally was thought to possess thea-configuration 165) was the sole exception to correlation between theconfigurations now reported and those assigned previously.Owing to its importance in graded hydrolysis serious attention is beinggiven to the acid-reversion of monosaccharides.The major productsformed when glucose is heated in O.33~-sulphuric acid (with or withoutpretreatment with formic acid) are 1,6-anhydro-~-~-gluco-pyranose and-furanose. The remainder of the product consists of a group of glucosedisaccharides in which isomaltose and gentiobiose predominate.166 Theamounts of sugars so formed provide a guide to the quantities of reversionproducts likely to be encountered as artefacts in partial hydrolysates ofpolyglucoses.The acid reversion of D-mannose yields a complex mixtureof di- and oligo-saccharides from which 6-0-a- and 6-O-p-~-mannopyranosyl-D-mannose and (?)-4-O-p-~-mannopyranosyl-~-rnannose have been ob-tained.167 L-Arabinose is converted in part into 3- and 4-O-P-~-arabo-pyranosyl-L-arabinose together with other di- and tri-sa~charides.~~~~ 168Acid-reversion of D-xylose gives a mixture of oligosaccharides, five of whichwere isolated, namely, xylobiose, O-a-D-xylopyranosyl a-D-xylopyranoside,and 3-O-ct-~-xylopyranosyl-~-xylose and its corresponding 2- and 4-0-is0mers.16~ Obviously the isolation of a-linked xylose-containing di-saccharides on hydrolysis of a xylose-containing polymer should be treatedwith reserve.The production of a single disaccharide of this type is anindication that it is not an artefact. Reversion of 2-acetamido-2-deoxy-~-glucose with moist hydrogen chloride yields a series of oligosaccharides fromwhich 2-acetamido-6-0-(2-acetamido-2-deoxy-a- and -p-D-glucopyranosy1)-2-deoxy-~-glucose has been isolated and characteri~ed.~~~Periodate Oxidation.-The sequence in which sodium periodate attacksthe a-glycol groups of monosaccharides was investigated for aldo-hexoses and-pentoses.l71 It was concluded that oxidation of aldoses proceeds ex-clusively by stepwise oxidation from the hemiacetal grouping down the163 A.J. Charlson, P. A. J. Gorin, and A. S. Perlin, Canad. J . Chem., 1956, 34, 1811;1957, 35, 365; cf. P. A. J. Gorin and A. S. Perlin, ibid., 1958, 36, 999.164 P. A. J. Gorin and A. S. Perlin, ibid., 1957, 35, 262.166 R. L. Whistler and D. F. Durso, J . Amer. Chem. SOC., 1950, 72, 677.166 S. Peat, W. J. Whelan, T. E. Edwards, and (Mrs.) 0. Owen, J., 1958, 586.167 J. K. N. Jones and W, H. Nicholson, J., 1958, 27.168 Cf. F. A. H. Rice, J . Amer. Chem. SOG., 1956, 78, 6167; L. Hough and J. B.169 D. H. Ball and J. K. N. Jones, J., 1958, 33.170 A. B. Foster and D. Horton, J., 1958, 1890.171 S. A. Warsi and W. J. Whelan, Chem. and Ind., 1958, 71; cf. F. S. H. Head,Pridham, Chem. and Ind., 1957, 1178.ibid., p. 360OVEREND: CARBOHYDRATES.329molecule. There is further evidence that sugars are oxidised in their cyclicforms, with the formation of intermediary esters.172 Differing rates ofhydrolysis of these esters have been related to the inductive effects of electro-philic groups in the alcohol component (5-8; R = CO,H > CHO >CH,*OH > Me, H). Cyclic acetal structures have been proposed for theRCHO4O--H&O\CHO + OHC HO <>H,OH --+ OHC+ 2H.CO2HOH (6) R 1 (7) A-(5) OHC+OHperiodate-oxidation products of g l y c ~ s i d e s , ~ ~ ~ their 4 : 6-O-benzylidene 174and 6-deoxy-derivatives.l75 A similar situation is found in periodate-oxidised polysac~harides.~~~ A steric effect in the oxidation of glycosideshas been noted.l77Anhydrides.-It has been demonstrated that in the sugar series a neigh-bouring trans-0-acetyl group exerts a directive influence on the scission ofan ethylene oxide by acidic reagents, and carbonium-type intermediateshave been suggested.178 Treatment of methyl 2,3-anhydro-4,6-0-benzyl-idene-a-D-guloside with 0.1N-sulphuric acid gives mainly 3,6-anhydro-~-ga1acto~e.l~~ When the corresponding 2,3-anhydro-alloside, -mannoside,and -taloside were similarly treated some 3,6-anhydro-products were formed.It was shown that loss of the glycosidic methoxyl group precedes anhydrideformation.The formation of 3,6-anhydro-sugars from the 2,3-anhydrideshas hitherto been noted only under alkaline conditions. The productfrom the alkaline treatment of methyl 2,3-di-O-benzoyl-4-0-tosyl-6-0-trityl-a-D-glucoside (9) is a mixture of methyl 3,4-anhydr0-6-0-trityl-a-D-galactoside (10) and methyl 2,3-anhydro-6-0-trityl-a-~-guloside (1 1 ;R = CPh,) .180 The ammonolysis of methyl 2,3-anhydro-~-ribofurano-179 L.Hough, T. G. Taylor, G. H. S. Thomas, and B. M. Woods, J., 1958, 1212.173 I. J. Goldstein and F. Smith, J . Amer. Chem. SOC., 1958, 80, 4681.174 R. D. Guthrie and J. Honeyman, Chem. and I n d . , 1958, 388.175 I. J. Goldstein, B. A. Lewis, and F. Smith, J . Amer. Chem. SOC., 1958, 80, 939.176 I. J. Goldstein and F. Smith, Chem. and I n d . , 1958, 40.177 E. F. Garner, I. J. Goldstein, R. Montgomery, and F. Smith, J . Amer. Chem,179 J. G. Buchanan, J., 1958, 2511.179 Idem, Chem. and Ind., 1958, 654.180 Idem, J., 1958, 995.Soc., 1958, 80, 1206330 ORGANIC CHEMISTRY.side has been reported.lsl Methyl 4,5-0-benzylidene-%O-tosyl-a-~-altro-side shows extreme lability and is converted into methyl 2,3-anhydro-4,6-O-benzylidene- a-D-alloside by acid-washed alumina.la2 4,1’,6’-Tri-0-tosylsucrose penta-acetate is converted by sodium methoxide into 3,6-anhydro-a-~-ga~actopyranosy~-l,4 :3,6-dianhydro-p-~-fructoside 162 (see p.327).The above-mentioned anhydroalloside, on treatment with ammoniaand subsequent N-acetylation, gives methyl 2-acetamido-4,6-O-benzylidene-2-deoxy-a-D-altroside (as monohydrate) which on total hydrolysis affords2-amino-l,6-anhydro-2-deoxy-~-~-altropyranose.~~~ Mechanisms of anhy-dride formation in sugars have been discussed.lWW. G. 0.12. THE NUCLEIC ACIDSIT is the purpose of this Report, covering work carried out mainly duringthe past two years, to give a general indication of the trends in nucleic acidresearch and then to give a more detailed discussion of a few aspects whereprogresss has been considerable.There has been less emphasis on theorganic chemistry of the acids, but the number of papers on physicochemicaland biophysical aspects of the subject has risen.Much work continues to be devoted to the synthesis of analogues of thenaturally occurring heterocyclic bases, nucleosides, and nucleotides and totheir incorporation into the nucleic acids of organisms. These studies are,for the most part, related to questions of cancer chemotherapy and chemicalmutagenesis.l The biosynthesis of nucleotides, or, more generally, theenzymology of nucleic acids, purines, and pyrimidines, continues to receivemuch attention.2 Rapid progress is being made in the study of nucleic acidfunction.The relationship of deoxyribonucleic acids (DNA) to the centralproblems of genetics is now firmly founded. The intense interest in thisfield is made clear in the published proceedings of a symposium on “ TheChemistry of Heredity,’’ where enlightening papers on a wide variety oftopics involving the nucleic acids are collected. The closely related studyof ribonucleic acids (RNA) in protein synthesis is also making rapidh e a d ~ a y . ~Progress has been made, and is reported on below, in the study of thenucleic acids from the point of view of their conformations and hydro-dynamic properties in solution and of the processes involved in theirdenaturation. Much congruous information is being obtained by physico-chemical studies of biosynthetic polyribonucleotides.It is evident that181 C. D. Anderson, L. Goodman, and B. R. Baker, J . Amer. Chem. SOL, 1958, 80,188 K. S. Ennor, J. Honeyman, C. J. G. Shaw, and T. C. Stening, J., 1958, 2921.18s A. B. Foster, M. Stacey, and S. V. Vardheim, Nature, 1957, 180, 247; Acta184 F. Micheel and A. Klemer (with R. F!ftsch), Chem. Bey., 1958, 91, 194.1 Cf. Ciba Foundation Symposium on The Chemistry and Biology of Purines,”2 L. A. Heppel and J. C . Rabinowitz, Ann. Rev. Biochem., 1958, 27, 613.3 “ The Chemistry of Heredity,” Ed. McElroy and Glass, The Johns Hopkins Press,4 R. B.Loftfield, Progr. Biophysics Bio$hys. Chem., 1957, 8, 347.5247.Chem. Scand., 1958, 12, 1605.Churchill and Co., London, 1957.Baltimore, 1957BROWN: THE NUCLEIC ACIDS. 331with a few possible exceptions the isolated nucleic acids are polydispersemixtures of different molecular species with the same general structure, sothat a direct attack on nucleotide sequence has not been possible. Instead,methods of determining the degree of randomness of distribution have beeninvestigated and the fractionation of isolated nucleic acids and the isolationof nucleic acids from particular cell fractions have received more attention.With the much clearer understanding of nucleic acid structure available,attention is being directed, anew, to the isolation and characterisation ofnucleoprotein~.~ Of these the viruses represent a special case and a greatdeal of structural information is now available, particularly on tobaccomosaic virus, largely through X-ray crystallographic work.6Ribonucleic Acids.-The general structure of RNA as a 3’,5’-linkedpolynucleotide has not been questioned.Branching through phosphotri-ester linkages in a bacterial RNA and in intact tobacco mosaic virus RNAhas been rendered very improbable, in confirmation of earlier work. Ofexceptional interest are the discoveries of bases other than the long-recognised adenine, guanine, cytosine, and uracil. Littlefield and Dunnhave found thymine (1 ; R = Me), 2-methyladenine (Z), 6-methylamino-purine (3; R = H, R’ = Me), and 6-dimethylaminopurine (3; R = R’ =Me) in ribonucleic acids from several sources, including yeast. Liver(1) (2) (3) (4) (5)microsome RNA contains the last two.The methylated guanine derivatives(4; R = H, R = Me; and R = R’ = Me) and (5) are also rather wide-spread.10 They occurin minute quantities, corresponding to 1 4 . 0 5 % of the uracil residues, butappear to be linked into the nucleic acid in the usual manner since, in mostcases, the corresponding nucleosides and nucleotides have been demon-strated after appropriate degradation. The question arises whether thesetrace-components are distributed through all the nucleic acid molecules inthe isolated material or whether they are functional components of particularacids contained in the specimen.Some support for the latter view is foundin the distribution of a new component nucleotide detected in yeast 1 2 9 1 35 J. A. V. Butler and P. F. Davison, Adv. Enzymol., 1957, 18, 161.6 R. E. Franklin and K. C. Holmes, Biochim. Biophys. Actu, 1956, 21, 405; R. E.Franklin in Symposium on “ Protein Structure,” Ed. Neuberger, Methuen, London,1958, p. 271.7 R. A. Cox, A. S. Jones, G. E. Marsh, and A. R. Peacocke, Biochim. Biophys. Aclu,1956, 21, 576. * D. E. Koshland, N. S. Simmons, and J. D. Watson, J . Amer. Chem. SOC., 1958,80, 1005.10 M. Adler, B. Weissman, and A. B. Gutman, J . Biol. Chem., 1958,230, 717; D. B.Dunn and J. D. Smith, Proc. IVth Internat. Congr. Biochem., Vienna, 1958.11 H. Amos and M. Korn, Biochim. Biophys.Acta, 1958, 29, 444.12 E. F. Davis and F. W. Allen, J . Biol. Chem., 1957, 227, 907.13 W. E. Cohn, Fed. PYOG., 1958,17,203: J . Amer. Chem. Sot., 1959,81, in the press.5-Methylcytosine has been found in E. coli RNA.11J. W. Littlefield and D. B. Dunn, Nulure, 1958, 181, 254332 ORGANIC CHEMISTRY.and pancreatic RNA; l4 this is particularly concentrated in the ‘‘ soluble ”RNA fraction.l2, l4 The corresponding nucleoside appears to be uniquelydistinguished from those previously isolated in that its chemistry is indicativeof a C-glycoside; the linkage is not broken by acid. Other evidence suggestsa 5-substituted uracil structure and (1; R = ribofuranosyl) is proposed.13Kemp and Allen l4 also reported other unidentified components in theguanylic acid fraction of hydrolysates of these ribonucleic acids.Several papers have described attempts to fractionate isolated ribo-nucleic acid.Elution from “ ECTEOLA ”-cellulose anion-exchange columnswith phosphate buffer gives different elution patterns for RNA isolated fromdifferent sources and from the same source by different methods;15 allfractions are heterogeneous. Other methods include precipitation withneutral salts l6 and counter-current distribution in 2-methoxy- or 2-butoxy-ethanol-phosphate systems.17 Two nuclear and one cytoplasmic (micro-somal) fraction have been separated from several tissues, and their baseratios and metabolic activity studied.ls The cytoplasmic RNA of cellsappears to be divided between the microsomes and a “ soluble ” fraction ofrelatively low molecular weight of which l0-20% is very activernetab~lically.~~ The “soluble” RNA is a necessary component in theearly stages of protein synthesis.20 Evidence has been given21 that foractivity the terminal nucleotide sequence must be as in (6; R = H) whereA and C represent adenine and cytosine residues ; P-amino-acyl derivativesof adenosine-5’ phosphate 22 then transfer the amino-acidto the residue (6; R = H) to give a 2’- or 3’-ester (6;R = amino-acyl).The evidence for the position of theamino-acid residue rests on the removal by ribonuclease ofan adenosine ester of the amino-acid which is periodate-insensitive until hydroly~ed.~~ The enzymic introductionof the adenine and cytosine nucleotides has been (6)studied.21,24>25 Hoagland 26 has recently reviewed the rapid developments inthis field.It should be realised that, since tracer methods are used,evidence for a terminal sequence as in (6) is not an indication of its presencein all the isolated soluble RNA: the amount may only be a fraction of thetotal.TheAOHOR “P .- J P lMost isolated ribonucleic acids are probably complex mixtures.14 J. w. Kemp and F. W. Allen, Biochim. Biophys. Acta, 1958, 28, 51.15 D. F. Bradley and A. Rich, J . Amer. Chem. SOC., 1956, 78, 5898.16 K. MiUra, T. Kitamura, and Y. Kawade, Biochim. Biophys. Acta, 1958, 27, 420.17 K. S. Kirby, Biochem. J., 1958, 68, 1 3 ~ .18 y. Hotta and S. Osawa, Biochim. Bi0phy.b. A C I Z , 1958, 28, 642.19 H. T. Shigeura and E.Chargaff, ibid., 1958, 30, 434.20 M. B. Hoagland, M. L. Stephenson, J. F. Scott, L. I. Hecht, and P. C. Zamecnik,21 L. I. Hecht, P. C. Zamecnik, M. L. Stephenson, and J. F. Scott, ibid., 1958, 233,22 Symposium on “ Amino Acid Activation,” BOG. Nut. Acad. Sci., U.S.A., 1958,2s H. G. Zachau, G. Acs, and F. Lipmann, ibid., p. 885.24 L. I. Hecht, M. L. Stephenson, and P. C. Zamecnik, Biochim. Biophys. Acta, 1958,2s E. S. Cannellakis, ibid., 1957, 25, 217.26 M. B. Hoagland, Proc. IVth Internat. Congr. Biochem., Vienna, 1958.J . Biol. Chem., 1958, $281, 241.954.44, 67.29, 460BROWN: THE NUCLEIC ACIDS. 333earlier claim that RNA from tobacco mosaic virus had both 3’- and 5’-phos-phate end groups has been reconsidered and there is now no evidence for thelatter type; 27 probably the earlier work was carried out on degradedmaterial. Recent work leads to the belief that there is one nucleic acidmolecule in an infective particle.This should correspond to a calculatedmolecular weight of 2-3 x lo6. A value of 2.1 x lo6 was found bysedimentation studies of RNA isolated by the phenol method.28 Measure-ments of intrinsic viscosity indicate that the RNA is in the form of a flexible,moderately coiled chain several thousand A in length,29J0 which findsconfirmation in electron-micrographical studies.32 The kinetics of chainbreaking by, e.g., ribonuclease30 or heat,31 show that nearly every breakcaused degradation and it is concluded that the molecule, unlike DNA, issingle-stranded. The large drop in optical rotation and increase in ultra-violet absorption consequent on mild degradation are thought to indicate asuperstructure retained by hydrogen bonds between contiguous nucleotideresidues2* Deamination can be effected without chain scission, and alter-ation of only a very few of the residues is sufficient to cause loss of infec-tivity or, possibly, m ~ t a t i o n .~ ~ ~ ~ If the molecular weight of 2 x lo6 isconfirmed the question of a 3’- or 5’-phosphate end group must presumablybe reopened since the earlier methods were insufficiently sensitive to detectone nucleotide in 6000. There is a real possibility that the isolated tobaccomosaic virus RNA which has retained its infectivity is one molecular species;the advantages of this for chemical studies are obvious.Staehelin 35 hasmade a close study of the reaction of the RNA with [14C]formaldehydeunder various conditions.Methods of degradation of RNA which break internucleotide linkagesare now well understood. Little, heretofore, has been done to effectremoval of the purine and pyrimidine residues. Hydrazine, applied earlierto the preparation of ribose phosphates from uridine and cytidine phos-phates, reacts with RNA to give a product almost devoid of pyrimidine basesand with an increased reducing capacity, but no evidence for the molecularweight of the “ ribo-apyrimidinic acid ” was given.36 The reaction ofbromine with nucleosides and nucleotides has received further at tention.37~ 38Purine derivatives are relatively inert but addition of bromine water (2 mol.)causes loss of light absorption in uracil and cytosine derivatives.Theproducts react with mild alkali giving substances, possibly acyclic, which areeasily split by acid, to ribose or ribose phosphate; 38 application to poly-nucleotide degradation may be a possibility.27 K. K. Reddi and C. A. Knight, Nature, 1957, 180, 374; R. E. F. Matthews and28 A. Gierer, Nature, 1957, 179, 1297.29 Idem, 2. Naturforsch., 1958, 13b, 477.30 Idem, ibid., p. 485.31 W. Ginoza, Nature, 1958, 181, 958.32 R. G. Hart, Biochim. Biophys. Acta, 1958, 28, 457.33 A, Gierer and K.-W. Mundry, Nature, 1958, 182, 1457.34 H. Schuster and G. Schramm, Z . Naturforsch., 1958, lsb, 697.35 M. Staehelin, Biochim. Biophys. Acta, 1958, 29, 410.36 S.Takemura, J . Biuchem. (Japan), 1957, 44, 321.37 T. Suzuki and E. Ito, ibid., 1958, 45, 403.38 W. E. Cohn, Biochem. J., 1956, 64, 28 P.J. D. Smith, ibid., p. 375334 ORGANIC CHEMISTRY.The varied effects of radiation, some of which are reversible, on livingorganisms are a continual source of interest and certainly in some of thesethe nucleic acids are involved. Several studies have been based on theoriginal observation by Sinsheimer, that ultraviolet irradiation of uridylicand cytidylic acid 39 in aqueous solutions leads to loss of ultraviolet absorp-tion and that this can be recovered by mild treatment by heat or dilute acid.The reversible photolysis of uracil gives 4,5-dihydro-4-hydroxyuracil (7) ,*Oand that of lJ3-dimethyluracil the corresponding derivative (8),41 bothstructures being confirmed by synthesis.Further irradiation of com-pound (8) gives NN’-dimethylmalonamide (10) via the barbituric acidderivative (9).42 At least three different reactions occur on irradiation ofuracil in aqueous solution, of which the first alone is reversible.& Thesensitivity of bases, especially thymine, to ultraviolet light is different in thefrozen state from that in aqueous solution.44 Shugar and Wierzchowski 45have made a study of quantum yields and reversibility in the photolysisof many pyrimidines. Hydrogen-bonding between the pyrimidine andthe sugar rings in nucleosides seems to play an important part in thereaction. Indirect evidence is obtained for about l0-15% reversibilitywith RNA, but a greater value is obtained with apurinic acid.Irradiationwith X-rays causes the formation of labile phosphate esters from purineand pyrimidine nucleotides in aqueous solution,46 and of guanine and2,4-diamino-5-formamido-6-hydroxypyrimidine from guanylic acid andg~anosine.~’Deoxyribonucleic Acid.-The chemistry of deoxyribonucleosides andnucleotides has been reviewed.@ In addition, this period has seen the firstsyntheses of natural deoxynucleosides, viz. , 2’-deo~yuridine,~~ thymidh1e,4~, 50and 2’-deo~yadenosine.~l 6-Methylaminopurine (3; R = H, R’ = Me)must now be added to the bases found in DNA.5239 R. L. Sinsheimer, Radiation Res., 1957, 6, 121.40 A. M. Moore, Canad. J . Chem., 1958, 36, 281.4 1 S. Y .Wang, M. Apicella, and B. R. Stone, J . Amer. Chem. Soc., 1956, 78, 4180.42 S. Y . Wang, ibid., 1958, 80, 6196.43 A. Rorsch, R. Beukers, J. Ylstra, and W. Berends, Rec. Truv. chim., 1958, 1’7,44 R. Beukers, J. Ylstra, and W. Berends, ibid., p. 729.45 D. Shugar and K. L. Wierzchowski, Biochim. Biophys. Acta, 1957, 23, 657; 1957,46 M. Daniels, G. Scholes, and J. Weiss, J., 1956, 3771.47 G. Hems, Nature, 1958, 181, 1721.48 A. M. Michelson, Tetrahedron, 1958, 2, 333.49 D. M. Brown, D. B. Parihar, C. B. Reese, and (Sir) Alexander Todd, J., 1958, 3035.fO G. Shaw and R. N. Warrener, Proc. Chem. Soc., 1958, 81.5 1 C. D. Anderson, L. Goodman, and B. R. Baker, J . Amer. Chem. Soc., 1958, 80,52 D. B. Dunn and J. D. Smith, Biochem. J . , 1958, 68, 627.423.25, 355.6453BROWN: THE NUCLEIC ACIDS.335As with RNA, it is clear that isolated DNA is a mixture of differentspecies varying in molecular weight 53 and, presumably, in nucleotidesequence. Chromatographic fractionation has been On calc-ium phosphate columns, DNA can be separated from products of deoxy-ribonuclease degradation of high molecular weight. Bendich and hisco-workers 56957 find that * ' ECTEOLA "-cellulose anion-exchange columnshave excellent resolving power, giving extensive fractionation with quantit-ative recovery. They conclude that molecular size and shape are importantfactors in the fractionation and are able to separate DNA from polyadenylicacid and from a DNA of identical source but in which 5-bromouracil partlyreplaces thymine.The results of fractionation of bacterial transformingfactors have been discussed.58 The DNA fractions obtained in this workshow considerable variation in base ratios. While the purine : pyrimidineratio is always close to unity, rather wide variations in the adenine : thymineand guanine : cytosine ratios are noted. This is at variance with the strictbase complementarity usually associated with the base-pairing in the double-helical DNA structure due to Watson and Crick; Donohue and Stent havediscussed other possible base-paired systems.59 One other observationbriefly noted by Bendich et aL5' is of considerable interest although as yetunexplained. Suspensions of " ECTEOLA "-cellulose appear to causepolymerisation of monodeoxyribonucleotides and of dialysable fractionsformed by deoxyribonuclease action on DNA ; non-dialysable products areformed, susceptible to deoxyribonuclease digestion.If, as is currently believed, DNA's have molecular weights of severalmillion and are mixtures, it is not at all clear how chemical end-group andsequence determinations can be made.Several studies take a less ambitiousobjective and attempt to discover whether the overall nucleotide arrange-ment does or does not correspond to a mathematically randomdistribution of the four major component mononucleotides. This involvesbreaking the molecules into smaller fragments and relating the amount ofeach produced to that expected from calculation, or comparing the amountsfrom DNA specimens from diverse sources.In this way Astrachan andVolkin 6o have detected chromatographic differences between two 'phageDNA's when these were degraded by heat to give large polynucleotides, butnot at the level of deoxyribonuclease degradation products ; thus, at higherlevels of organisation differences appear. Jones and Stacey have continuedtheir study of the degradation products derived from apurinic acid thio-acetals, the basis of which was discussed in Ann. Reports, 1956,53,265. Theyconclude that the nucleotides in the DNA of Mycobacterium Phlei are not53 C. Sadron, J. Pouyet, and R. Vendrely, Nature, 1957, 179, 263; J. A. V. Butler,D. J. R. Laurence, A. B. Robins, and K. V. Shooter, ibid., 1957,180, 1340.54 G. Semenza, Arkiv Kemi, 1957, 11, 89.55 R.K. Main and L. J. Cole, Arch. Biochem. Biophys., 1957, 68, 186.56 M. Rosoff, G. di Mayorca, and A. Bendich, Nature, 1957, 180, 1355.57 A. Bendich, H. B. Pahl, G. C. Korngold, H. S. Rosenkranz, and J. R. Fresco,58 A. Bendich, H. B. Pahl, and S. M. Beiser, Cold Spring Harbor Symp. Quant. Biol.,59 J . Donohue and G. S. Stent, Proc. Nat. Acad. Sci., U.S.A., 1956, 42, 734.60 L. Astrachan and E. Volkin, J. A m y . Ckem. SOC., 1957, 79, 130.J . Amer. Chem. SOC., 1958, 80, 3949.1956, 21, 31336 ORGANIC CHEMISTRY.randomly distributed.61 Chargaff and his co-workers have extended theirwork on the acid-degradation of DNA and the chromatographic fraction-ation 62 and estimation of the products.63 In acid, DNA rapidly loses purineresidues, and the apurinic acid formed then breaks down by an eliminationyielding nucleoside-3’,5’ diphosphates and oligonucleotides of the generalform Py(n)*P(n + 1).Some confirmation of this mechanism is afforded bya study of the degradation of a series of dideoxynucleotides. Understandard hydrolytic conditions specimens of DNA from ten sources werefound to give product patterns indicating wide variations in pyrimidinenucleotide distribution; at least 70% of the pyrimidines occurred as oligo-nucleotide tracts containing three or more residues in a row. Generally thearrangement is considered to be far from random. In these experiments,further acid-degradation of the initially produced fragments had to beallowed for, eg., the conversion of nucleoside diphosphates into monophos-phates. In a valuable contribution, Burton and Peterson show that DNAis degraded by 66% formic acid containing 2% of diphenylamine (but not inits absence), with negligible production of monophosphates.The mechanismof this reaction is not clear, but phosphate elimination in the intermediateapurinic acid may be facilitated by enamine formation. They conclude, inagreement with others, that there is a bias against sequences of the type-PUT-Py- p-Pu- in DNA.Results complementary to the above should be obtained by the degrad-ation of “ deoxyribo-apyrimidinic acid.” Takemura 65 claims to haveprepared this material by reaction of DNA with hydrazine; 20-30% of theproduct remains undialysable; this is devoid of pyrimidine bases, and theadenine : guanine ratio remains unaltered.Treatment of this with diluteacid or of apurinic acid with hydrazine is claimed to give material consideredto be poly(deoxyribose phosphate). Further details would be welcome, butit should be noted that titration studies 66 indicate a chain length for dialysedapurinic acid of only ten nucleotide units, considerably smaller than earlierestimates.The purines are more reactive than the pyrimidines of DNA towardsalkylation by methyl sulphate or by “ nitrogen mustard.’’ 67768 Reactionat the 7-position is demonstrated by the isolation of 7-methylguanine 68after alkylation of deoxyguanylic acid ; the glycosidic linkage in theintermediate is very labile. X-Irradiation of DNA has been studiedf urt her.69Kornberg and his co-workers have achieved, for the first time, the61 A.S. Jones, M. Stacey, and B. E. Watson, J., 1957, 2454; A. S. Jones and62 W. E. Cohn and E. Volkin, Biochim. Biophys. Acta, 1957, 24, 359.63 H. S. Shapiro and E. Chargaff, ibid., 1957, 23, 451; 26, 596, 608.64 K. Burton and G. B. Peterson, ibid., 1957, 26, 667.65 S. Takemura, ibid., 1958, 29, 447.66 E. Hurlen, S. G. Laland, R. A. Cox, and A. R. Peacocke, Act& Chem. Scand.,67 B. Reiner and S. Zamenhof, J . Biol. Chem., 1957, 228, 475.68 P. D. Lawley, Biochim. Biophys. Acta, 1957, 26, 450; Proc. Chem. SOC., 1957,69 M. Daniels, G. Scholes, J. Weiss, and C. M. Wheeler, J . , 1957, 226.M. Stacey, Chem. SOC. Special Publ., 1957, No. 9, p. 129.1956, 10, 793.290BROWN: THE NUCLEIC ACIDS.337biosynthesis of DNA in a cell-free An enzyme from E. coliextracts has been purified over 2000-fold and has been shown to catalysethe conversion of a mixture of the four deoxynucleoside-5’ triphosphates toa material behaving like DNA, with concomitant release of pyro-ph~sphate.~O Highly polymerised DNA and Mg++ must be present.Omission of any one component reduces the rate of synthesis to 0.5%.A net synthesis of more than ten times the weight of DNA primer addedhas been obtained and the new DNA has the natural 3’,5’-internucleotidelinkage.71 Substitution of substrate analogues for the natural nucleosidetriphosphates allows their incorporation and, for example, deoxyuridinetriphosphate incorporates uracil specifically in place of thymine,72 givingadditional support for Watson and Crick’s base-pairing hypothesis.Theenzymic reaction between DNA and a single deoxynucleoside triphosphateleads, apparently, to the addition of one or, a t the most, a very few nucledtideresidues to the end of the DNA chain; it is pointed out that this may be ofvalue in end-group determination^.^^ Davidson and his co-workers haveshown the incorporation of rHlthymidine into DNA-like material inextracts of mammalian cells, increased by addition of DNA to the system.740 T T T T T THO-7-HO. .-( ‘ I )The chemical synthesis of DNA-like molecules is far from sight, butKhorana et al. have devised methods for the preparation of oligodeoxy-nucleotides. Basically, they effect the condensation between a monoalkylphosphate and an alcohol by means of toluene-9-sulphonyl chloride orpreferably, dicyclohexyl carbodi-imide in anhydrous pyridine.In this waythey have prepared several dideoxynucleotides by condensation of protectedintermediate^.^^ The reaction with thymidine-5’ phosphate (1 1) alone ledto polymerisation, and oligomers (12; n = 0-3) were separated from thereaction mixture by chromatography on cellulose anion-exchangers and~haracterised.~~ Cyclic oligonucleotides (13) were formed concurrently andthese too were isolated.In many discussions of the conformational aspects of the DNA macro-molecule, the hydrogen-bonded double-helical structure is a basic tenet.70 I. R. Lehman, M. J. Bessman, E. S. Simms, and A. Kornberg, J .B i d Chem.,1958, 233, 163.71 M. J. Bessman, I. R. Lehman, E. S. Simms, and A. Kornberg, ibid., p. 171.72 &I. J. Bessman, I. R. Lehman, J. Adler, S. B. Zimmerman, E. S. Simms, and73 J. Adler, I. R. Lehman, M. J. Bessman, E. S. Simms, and A. Kornberg, ibid., p.74 J. N. Davidson, R. M. S. Smellie, H. M. Keir, and A. H. McArdle, Nature, 1958,75 P. T. Gilham and H. G. Khorana, J . Amer. Chem. SOC., 1958, 80, 6212.713 G. M. Tener, H. G. Khorana, R. Markham, and E. H. Pol, ibid., 1958, 80, 6223;A. Kornberg, Proc. Nat. Acad. Sci., U.S.A., 1958, 44, 633.641.182, 589.W. E. Razzell and H. G. Khorana, ibid., p. 1770338 ORGANIC CHEMISTRY.More detailed descriptions of the A and the B form based on refined X-raystudies have been given 77 and a newly discovered (C) form of the lithiumsalt, formed reversibly from the B form, has been described.78 A modelconsistent with the X-ray data is related to the B form by moving the basepairs 2 A away from the helical axis and tilting them by about 5", and thereare 9.3 base pairs per turn of the helix.A detailed infrared-spectral studyof the sodium salt of DNA gives results regarding molecular configurationsin accord with those from X-ray work.79 Of exceptional interest are experi-ments by Meselson and Stahl,80 who observed the distribution of 15N amongmolecules of bacterial DNA by density gradient centrifugation followingtransfer of a uniformly 15N-substituted E. coli population to a 14N-medium.They find: " (1) that the nitrogen of a DNA molecule is divided equallybetween two subunits which remain intact through many generations ;(2) that, following replication, each daughter molecule has received oneparental subunit; and (3) that the replicative act results in moleculardoubling." Thus the theory of DNA replication receives confirmation,although the mechanism remains a mystery.Shooter has reviewed the physical chemistry of DNA.*l The conform-ation of the DNA molecules in saline solution has been variously described,as, for example, that it is highly extended, although not rod-like, but gentlycoiled in a random fashion.82 More attention has been paid recently to theprocess of " denaturation " of DNA which results from changes in pH,ionic strength, and temperature, singly and in combination, and the actionof other reagent^.^^-^^ Denaturation occurs when a critical number of theintramolecular hydrogen-bonds are irreversibly broken, leading to apermanent loss of the helical configuration.It can be followed titrimetricallyand by changes in optical density and in molecular dimensions as determinedby, inter alia, sedimentation, viscosity, and light-scattering measurements.Reduction of the ionic strength of DNA solutions to low values causesd e n a t u r a t i ~ n , ~ ~ , ~ ~ a fact which vitiates some earlier studies. It is wellknown that when a saline solution of DNA is titrated from neutrality to77 R. Langridge, W. E. Seeds, M. R. Wilson, W. C. Hooper, M. F. H. Wilkins, and78 D. A. Marvin, M. Spencer, M. H. F. Wilkins, and L.D. Hamilton, Naturc, 1958,70 G. B. B. M. Sutherland and M. Tsuboi, Proc. Roy. Soc., 1957, A , 239, 446.80 M. Meselson and F. W. Stahl, Proc. Nat. Acad. Sci., U.S.A., 1958, 44, 671.81 K. V. Shooter, Prop. Biophysics Biophys. Chem., 1957, 8, 309.82 P. Doty, B. B. McGill, and S. A. Rice, Proc. Nut. Acad. Sci., U.S.A., 1958,44, 432.83 L. F. Cavalieri, M. Rosoff, and B. H. Rosenberg, J . Amer. Chem. SOC., 1956, 78,84 A. R. Peacocke, Chem. SOC. Special Publ., 1957, No. 8, p. 163.85 A. R. Matheson and S . Matty, J . Polymer Sci., 1957, 23, 747.86 R. A. Cox and A. R. Peacocky, ibid., p. 765.87 Idem, J., 1958, 4117.88 E. P. Geiduschek, J . Polymer Sci., 1958, 31, 67.8Q G. Zubay, Biochim. Biophys. Acta, 1958, 28, 644.QO P. Ehrlich and P. Doty, J .Amer. Chem. Soc., 1958, 80, 4251.91 S. A. Rice and P. Doty, ibid., 1957, 79, 3937.92 E. L. Duggan, V. L. Stevens, and B. W. Grunbaum, ibid., p. 4859.09 L. F. Cavalieri and B. H. Rosenberg, ibid., p. 5352.94 J. Hermans and A. M. Freund, J . PoZymer Sci., 1958, 28, 229.95 V. L. Stevens and E. L. Duggan, J . A m y . Chem. SOC., 1957, 79, 5703.L. D. Hamilton, J . Biophys. Biochem. Cytol., 1957, 3, 767.182, 387.5239BROWN: THE NUCLEIC ACIDS. 339pH 2-6 and back at 25", a hysteresis in the curve is noted, due to liberationof titratable basic groups, and the molecule becomes irreversibly collapsed.Titration to intermediate pH values leads to a family of backward-titrationcurves from which the degree of denaturation can be calculated, but if only10-15y0 of the hydrogen-bonds are broken these are re-formed on returnto neutrality.If 75% are broken the structure becomes unstable and rapiddisorganisation then leads to the completely denatured form.84@, 8'Hydrogen-bond breaking, it is supposed,89 involves protonation on N(l) of theadenine and cytosine residues. If the titration is carried out at orbelow 0" the curve becomes reversible and the DNA is not denat~red.8~988Geiduschek 88 comments that if, as is generally supposed, titration to pH 2.6involves the rupture of the hydrogen-bonds then the major contribution tothe stabilisation of the double-helix secondary structure is made by otherforces. Nucleates from different sources, it may be noted, also show stabilitydifferences,m the origins of which are unresolved.Denaturation by alkali is essentially similar to that caused by a~id.~OThere is a sharp transition a t pH 11.7-11.9, marked by a ten-fold loweringin intrinsic viscosity and a three-fold reduction in the radius of gyration with-out change in molecular weight.It is concluded that the denatured DNAconsists of randomly coiled, highly flexible chains that remain paired andhighly contracted owing to substantial numbers of non-periodically arrangedintramolecular hydrogen-bonds. This picture is also drawn of heat-denaturedDNA 91-94 in which the changes appear to be due to " melting out " of tractsof hydrogen bonds, i.e., a co-operative breakdown of the highly organisednative structure over a small temperature range.g1 Heat-deformed DNA canbe separated from unheated material by precipitation with lead ions.95DNA molecules can apparently be fragmented, with double chain-scission, leaving hydrogen-bonds intact, by sonic waves 82 and by passingsolutions through an a t ~ m i s e r , ~ ~ the latter method being claimed to giveessentially monodisperse material; y-rays appear to break both inter-nucleotide and hydrogen bondsg7Synthetic Polyribonuc1eotides.-The advantages of having availableoligo- and poly-nucleotides in which the nature of the constituent mono-nucleotides is controlled are obvious.In consequence a considerablevolume of work has appeared since the demonstration by Grunberg-Managoand Ochoa that an enzyme from Axotobacter vinelandii can catalyse thereversible formation of polynucleotides from nucleoside-5' diphosphates withloss of orthophosphate [viz., n nucleoside-5' PP =z+ (nucleoside-P)n + %PI.Similar enzymes have been detected in M .Zysodeikticus,98 in E. coZi,99 and inliver nuclei.100 The Azotobacter enzyme has been extensively purified 101and with this fraction a lag period in its action is noted which can beabolished by addition of polynucleotides lol or oligonucleotides 102 to the913 L. F. Cavalieri, J . Amer. Chem. SOC., 1957, 79, 5319.97 A. R. Peacocke and B. N. Preston, J . Polymer Sci., 1958, 31, 1.98 R. F. Beers, jun., Arch. Biochem. Biophys., 1958, 75, 497.99 U. 2. Littauer and A. Kornberg, J . Biol. Chem., 1957, 226, 1077.100 R. J. Hilmoe and L. A. Heppel, J . Amer. Chem.SOC., 1957, 79, 4810.101 S. Mii and S. Ochoa, Biochim. Biophys. Ada, 1957, 26, 445.102 M. F. Singer, L. A. Heppel, and R. J. Hilmoe, ibid., p. 447340 ORGANIC CHEMISTRY.system and, at least in the latter case, the primer becomes incorporated intothe polymer. Full details have now been given of the structures of thepolynucleotides containing one base and a mixture of bases.lo3 They areall 3',5'-linked polymers and by controlled degradation, mainly withenzymes, a valuable array of different oligonucleotides can be prepared(e.g., those represented by the symbols (14-18), and the correspondingA A A A A A A A U A A U~ p ~ p ~ p (18)dimers and tetramers). Phosphorolysis of these,lM and of a variety ofribonucleic acids,105 has been studied.Poly(rib0thymidine phosphate) hasbeen prepared from the synthetic 5-methyluridine-5' pyrophosphate.lWMichelson 107 has made substantial progress in chemical synthesis andhas obtained polymers containing one or more monomer types with averagechain lengths of up to twenty units, but in which both 2',5'- and 3',5'-inter-nucleotidic linkages are present. Nucleoside-2',3' phosphates (19) wereconverted into mixed anhydrides (20) by means of diphenylphosphoro-chloridate and, with base, polymerisation occurred. Hydrolysis of theintermediate (21) by water then gave the polynucleotide (22).B B B BThe biosynthetic polynucleotides have been extensively studied byphysicochemical methods ; changes in pH, ionic strength, metallic ions, and103 L. A. Heppel, P. J. Ortiz, and S. Ochoa, J . Biol. Chem., 1958, 229, 679, 695.lo4 M. F. Singer, ibid., 1958, 232, 211.105 S. Ochoa, Arch. Biochem. Biophys., 1957, 69, 119; P. Lengyel and S. Ochoa,106 B. E. Griffin, (Sir) Alexander Todd, and A. Rich, Proc. Nat:Acad. Sci., U.S.A.,10' A. M. Michelson, Nature, 1958, 181, 303.Biochim. Biophys. Acta, 1958, 28, 200.1958, 44, 1123BROWN: THE NUCLEIC ACIDS. 341temperature often have profound and inter-related effects on their structuresand interactions in solution. Thus polyadenylic acid in aqueous saltsolution consists of flexible, randomly coiled molecules .lo8 Reduction of thepH to below 5 causes an abrupt transition. Changes in the sedimentationconstant and viscosity occur and A,,, changes from 257 to 252 mp withincrease in optical density. The evidence suggests that a rigid, interruptedmultiple-helical structure has been formed composed of various numbers ofpolyadenylic acid mole~ules.~0~~~0~ It is suggested loS that the lowering ofthe electrostatic energy by titration of about half of the adenine groups isresponsible for the stability of the structure; no intermediate states are noted.The transition of this ordered structure to a random coil over a narrowtemperature range (near 75") is reminiscent of the similar behaviour of DNA,accounted for by co-operative breakdown of the inter-base hydrogen-bonds.X-Ray diffraction diagrams from polyadenylic acid fibres and two possiblemodels which find some agreement with them have been discussed.ll0Further work on the interaction between polyadenylic acid and poly-uridylic acid has appeared.ll1-ll6 By using a continuous variation techniquea 1 : 1 complex can be observed, stable a t pH 7.4 in salt solution and charac-terised by a lowered optical density. In presence of Mg++ or Mn++ anothercomplex, containing uracil and adenine in the ratio 2 : 1, can be discerned,less stable than the 1 : 1 complex.1119112 The hypochromic effect, infraredmeasurements,lf5 the breakdown of the complex at high and low pHvalues,l14 and the prevention of its formation by formaldehyde114 areconsistent with hydrogen-bonding between adenine and uracil residues inadjacent polynucleotide chains. Felsenfeld, Davies, and Rich 111,112 thinkthat the first complex is an interrupted double helix in which very few " gaps,''or non-hydrogen-bonded regions, are left 113 and that the second complex is atriple helix. Zubay 116 has discussed the need for Mgff in the formation ofthe latter and has proposed a model for the three-stranded molecule whichis consistent with preliminary X-ray diffraction results. Beers andSteiner 114 consider that the linear variation of optical density withadenine : uracil ratio would appear to make any abrupt transition from adoubly- to a triply-stranded structure unlikely.Thesubstance a t 66% humidity has an organised helical structure and a three-chain model seems to fit the crystallographic data best. A 1 : 1 and a 2 : 1complex between polyinosinic and polyadenylic acids is formed and opticaldensity changes (hypochromic effect) together with ultracentrifugation andPolyinosinic acid has been studied as fibres and in solution.117108 J. R. Fresco and P. Doty, J . Amer. Chem. Soc., 1957, 79, 3928.109 R. F. Steiner and R. F. Beers, jun., Biochirn. Biophys. A d a , 1957, 26, 336;R. F. Beers, jun., and R. F. Steiner, Nature, 1957, 179, 1076; R. F. Steiner and R. F.Beers, jun., J . Polymer Sci., 1958,31, 53; R. C. Warner, J . Biol. Chem., 1958, 229, 711.110 R. S. Morgan and R. S. Bear, Science, 1958, 127, 81.111 G. Felsenfeld and A. Rich, Biochirn. Biophys. Acta, 1957, 26, 457.112 G. Felsenfeld, D. R. Davies, and A. Rich, J . Amer. Chem. Soc., 1957, 79, 2023.11s G. Felsenfeld, Biochim. Biophys. Acta, 1958, 29, 133.114 R. F. Beers, jun., and R. F. Steiner, Nature, 1958, 131, 30.116 H. T. Miles, Chem. and Ind., 1958, 591; Biochim. Biophys. Acta, 1958, 27, 46.118 G. Zubay, Nature, 1958, 182, 388.117 A. Rich, Biochim. Biophys. Acta, 1958, 29, 502342 ORGANIC CHEMISTRY.X-ray studies are taken to indicate two- and three-stranded helicalstructures.ll* A helical complex is also formed between polyinosinic andpolycytidylic acids.llg The importance of these triple-helical structures tocurrent views on genetic information transfer has been stressed.112J20Michelson 121 has discussed the basis of the hyperchromic effect i.e. theincrease in optical density observed when polynucleotides (even di-nucleotides) 122 are hydrolysed or when organised structures such as DNAare denatured.D. M. B.D. M. BROWN.C. A. BUNTON.D. P. CRAIG.A. G. DAVIES.P. B. D. DE LA MARE.J. ELKS.T. G. HALSALL.W. D. OLLIS.W. G. OVEREND.J. E. SAXTON.K. SCHOFIELD.T. SWAIN.G. H. WHITHAM.G. H. WILLIAMS.11* A. Rich, Nature, 1958, 181, 521.119 D. R. Davies and A. Rich, J. Amer. Chem. SOC., 1958, 80, 1003.120 G. Zubay, Nature, 1958, 182, 1290.121 A. M. Michelson, ibid., p. 1502.122 M. Privat de Garilhe and M. Laskowski, J. B i d . Chem., 1956, 223, 661