摘要:

Synthesis of Protected 1‐Deoxy‐1‐nitroaldosesThe direct oxidation of the oxime1witht‐butyl hydroperoxide and vanadyl acetylacetonate yielding the nitro derivative2(54%,Scheme 1) could not be applied to other oximes. Diastereoselective bromination of the aldonolactone oxims7and10–12according to known procedures gave the corresponding bromonitroso compounds which were oxidized to the bromonitro compounds9, 14, 18and22, respectively. Oxidation of the bromonitroso compound in the D‐mannopyranose series proved difficult, but the corresponding chloronitro derivative23was easily obtained according toCorey&Estreicher(Scheme 2and3). The structure of the bromonitro compound9was determined by an X‐ray analysis, and the configurations of the bromonitro compounds14, 18and22were deduced from their molecular rotations. Reduction of the bromonitro compounds gave the protected 1‐deoxy‐l‐nitroaldoses2,15/16,19/20, and24/25, respectively, in good overall yields. The ribose derivatives15and16were detritylated to give the nitro compound4, and the mannose derivative2was partially deprotected to give the monoisopropylidene compound26. The nitro group shows a normal anomeric effect which is reflected in theIR. spectra of the pyranose derivatives

ISSN:0018-019X    

DOI:10.1002/hlca.19820650302

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractReaction of 9‐methyl‐cis‐decalin‐1,8‐dione (2) and of itstrans‐isomer (3) with (2R,3R)‐2,3‐butanediol (8) gives in both cases the monoacetals in high yield. While no enantiotopic differentiation is found for3, a strong preference for the (9S,10R)‐monoacetal9is found for thecis‐decalin‐dione2.The differentiation, reaching a maximal ratio of 9:1, is found to increase by conditions, which slow down the rate of reaction, e. g. lowering the temperature, the concentration of the acid catalyst, or by using a sterically encumbered catalyst. The use of this procedure for the preparation of optically active compounds is exemplified by the transformation of monoacetal 9 (obtained in 76% yield from2) into (9R, 10R)‐9‐methyl‐1‐decalone (12). The differing behaviour of diketones2and3is discussed in terms of

ISSN:0018-019X    

DOI:10.1002/hlca.19820650303

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractComplexes [MX2(1)] (M = Ni, Pd and Pt; X=Cl and NCS; 1 = 2,11‐bis(dialkyl‐[or diaryl]phosphinomethyl)benzo[c]phenanthrene; alkyl = cyclohexylt‐butyl; aryl =m‐tolyl,p‐anisyl andm‐CF3C6H4) have been synthesized.An NMR. study of the t‐butyl complexes provides evidence for a “fan‐like” motion of the benzo[c]phenanthrene moiety over the p

ISSN:0018-019X    

DOI:10.1002/hlca.19820650304

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractA study relating to the biological detoxification of resin acids is described. Abietic acid was transformed into a number of non‐toxic hydroxylated derivatives byMortierella isabellina.The biotransformation products have been identified and shown to be less toxic than abietic aci

ISSN:0018-019X    

DOI:10.1002/hlca.19820650305

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Technical Procedure for the synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophoroneTeil 4 dieser Reihe: [1].. V. Synthesis of AstaceneStarting from optically inactive astaxanthin intermediates, the highly oxygenated carotenoid astacene was synthesized in seven steps (55% overall yield from 6‐oxo‐isophorone). Key features of the new approach are base‐ and acid‐catalyzed rearrangements of acetylenic intermediates such as those described inSchem

ISSN:0018-019X    

DOI:10.1002/hlca.19820650306

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Steroselective Total Synthesis of Natural Phytol and Derivatives thereof; Use of these Compounds in the Synthesis of Natural Vitamin K1The Li2CuCl4‐catalyzed couplings of the easily accessible bifunctional C5allylic acetates (E)‐18aand (E)‐18bwith racemic hexahydrofarnesylmagnesium bromide ((3RS/RS, 7RS/SR)‐19a) proceed with high chemo‐ and stereoselectivity (≥98% (E)‐retention) to give the (2E, 7RS/RS, 11RS/SR)‐phytol derivatives1aand1b, respectively, in yields of 72–80% (Scheme 5). The same couplings performed with optically active hexahydrofarnesylmagnesium bromide (3R, 7R)‐19ayielded the (E)‐phytol derivatives of the natural series (7R, 11R)‐1aand (7R, 11R)‐1b.Acid‐catalyzed hydrolysis of(2E, 7R, 11R)‐1bgave natural phytol((2E, 7R, 11R)‐1c)Friedel‐Craftsalkylation of ‘menadiol monobenzoate’11bwith (2E, 7R, 11R)‐1aor (2E, 7R, 11R)‐1bgave the dihydrovitamine K1derivative (2E/Z, 7′R, 11′R)‐12b((E/Z)≈︁ 9:l). Conversion of configurationally pure (2E, 7′R, 11′R)‐12b(yield 73%; obtained after chromatographic removal of the (Z)‐isomer) into natural vitamine K1((2E,7′R, 11′R)‐2) was achieved in the usual way by saponification and oxidation with air.Some further investigations of the coupling reactions of bifunctional C5allylic synthons with hexahydrofarnesylmagnesium bromide (3RS/RS, 7RS/SR)‐19ashowed the outcome of these reactions to be critically dependent on the nature of the leaving group, the double‐bond geometry and the nature and concentration of the catalyst. Thus, the Li2CuCl4‐catalyzed couplings of (3RS/RS,7RS/SR)‐19awith the allylic halides29aand29cas well as withp‐toluenesulfonate29byielded besides the phytol derivatives1aand1b‐ also the SN2′‐type products30aand30b(Scheme 8,Table 2); the same result was found for the coupling with thecis‐configurated allylic acetates (Z)‐18aand (Z)‐18b(Table 3). A similar loss of chemo selectivity as well as the loss of stereoselectivity in the coupling reactions of19with the bifunctional (E)‐olefins of type18was observed when the Li2CuCl4‐catalyst concentration was increased from

ISSN:0018-019X    

DOI:10.1002/hlca.19820650307

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractEinige 7endo‐monosubstituierte Bicyclo[3.2.0]hept‐2‐en‐6‐one and Bicyclo‐[3.2.0]heptan‐6‐one zeigen eine unerwartete thermodynamische Stabilität gegenüber den entsprechenden 7exo‐Isomeren. Die basenkatalysierte Epimerisierung (NaOH oder N(CH2CH3)3) verschiedener 7‐monosubstituierter Bicyclo[3.2.0]‐hept‐2‐en‐6‐one (1‐7) und Bicyclo[3.2.0]heptan‐6‐one (8–10) führt je nach Substituent (R) zu folgenden endo/exo‐Gleichgewichtsgemischen: (a) Bicyclo[3.2.0]‐hept‐2‐en‐6‐one: R = F: 89/11, R = C1: 87/13, R = CH3: 76/24, R = CH2CH3: 65/35, R = CH (CH3)2: 57/43, R= C (CH3)3: 10/90, R= C6H5: 66/34; (b) Bicyclo[3.2.0]‐heptan‐6‐one: R = C1: 85/15, R = CH3: 45/55, R= C (CH3)3: 0,4/99,6. In jedem Fall wurde das gleiche Epimerengemisch erhalten, ausgehend sowohl vom endo‐ wie auch vom exo‐Isomeren.Die bemerkenswerte endo‐Stabilität wird einer Bevorzugung der Konformation 11 des Cyclobutanonringes zugeschrieben, verursacht durch geringere Pitzer‐Spannung. So kann ein endo‐Substituent an C(7) eine pseudoäquatoriale Lage am Cyclobutanonring einnehmen. Bei sehr sperrigen Substituenten mit zunehmender Raumerfüllung nimmt eine 1,2‐abstossende Wechselwirkung langsam überhand, bis im Falle des t‐Butylsubstituenten die exo‐Konfiguration die stabilere wird.Die Dehalogenierung von 7‐Halo‐substituierten Bicyclo [3.2.0]hept‐2‐en‐6‐onen (15 bis 21) mit Zink und Eisessig und mit Tributylzinnhydrid führte zu den folgenden endo/exo‐Epimerengemischen der entsprechenden 7‐monosubstituierten Bicyclo [3.2.0]hept‐2‐en‐6‐one (2 bis 7): R = C1: 92/8, R = CH3: 93/7, R = CH2CH3: 93/7, R = CH(CH3)2: 92/8, R = C(CH3)3: 93/7, R = C6H5: 93/7. In allen Fällen, also unabhängig vom Substituenten R, war das endo‐isomere stark bevorzugt. Es muss sich also um eine kinetische Kontrolle im isomerenbestimmenden Schritt handeln: Die Reduktion verläft über das Enolat, bzw. über eine Radikalspezies mit trigonal‐planarer Anordnung am C(7

ISSN:0018-019X    

DOI:10.1002/hlca.19820650308

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractActivation parameters have been determined for the intramolecular site exchange of the carbonyl groups in tricarbonyliron complexes of 1,4‐ and 2,3‐disubstituted 1,3‐butadienes, of 1,3‐cycloalkadienes and of 1,2‐dimethylidene‐cycloalkanes by temperature‐dependent13C‐NMR. spectroscopy (seeTable 1). The variations of the activation parameters are discussed in terms of a turnstile‐type mechanism for the exchange process and of the differences in the ground state and transition state stability of the complexes. A VB‐model of the complexes is used to explain the difference

ISSN:0018-019X    

DOI:10.1002/hlca.19820650309

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractReaction of the nitrone1with α‐chloroacrylonitrile (4) as ketene equivalent yields the 5‐isoxazolidinone2aand the α‐chloroimine5. The mechanism of the reaction is discussed. The compound2ais useful for the synthesis of hindered pyrrol

ISSN:0018-019X    

DOI:10.1002/hlca.19820650310

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Crystal and Molecular Structure of Macrocyclic MUSKS. II.trans‐Civetone and its 2, 4‐DinitrophenylhydrazoneThetransandcisisomers of civetone (C17H30O) crystallize in isomorphous systems and form plastic crystals (tetragonal, space groupI41a=9.95 (4),c= 32.79 (1) Å,Z= 8). Mixed crystals were prepared withcis‐civetone as second component. Accordingly the diffuse structural model obtained for the disordered phase of thecis‐isomer [1] is also regarded as representative of that oftrans‐civetone.The crystal structure oftrans‐civetone 2,4‐dinitrophenylhydrazone (DNPHTC; C23H34N4, Monoclinic, Space groupP21/c,a=8.364(2),b=7.971(1),c=36.025(8) Å, β=91.44 (2)°) was solved by direct methods and refined to a finalRof 0.09 (Rw= 0.021). The macrocycle adopts a sexangular conformation [23*434*44*], and its mean plane is approximatively perpendicular to that of the aromatic substituent. Empirical force field calculations have shown that the DNPH substituent has very little influence on the macrocycle conformation. The intermolecular interactions take place essentially between groups of the same type: macrocycle…macro

ISSN:0018-019X    

DOI:10.1002/hlca.19820650311

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY