摘要:

AbstractA stereoselective synthesis of tricarbonyl‐[((1RS,2RS,4RS,5RS,6RS)‐C‐5,6,C‐η‐(5,6,7,8,‐tetramethylidenbicyclo[2.2.2]octan‐2‐ol)]iron (11),and of its tosylate12and benzoate13is reported. The bulk of the ‘endo’‐Fe(CO))3moiety and of the ester groups in13renders itsDiels‐Alderadditions to methyl propynoate (15)), butynone (16), and 1‐cyanovinyl acetate highly ‘para’ regioselective. The cycloadditions of diene‐alcohol11are either ‘meta’‐ or ‘para’‐regioselective depending on the nature of the dienophile. In the presence ofBF3.Et2O, the addition of11to methyl vinyl ketone is highly stereo‐ (Alder mode) and ‘para’‐regioselective, giving adduct52(tricarbonyl [((1RS,4RS,8RS,9RS,10RS,12RS)‐C,9,10,C‐η‐(12‐hydroxy‐9,10‐dimethylidenetricyclo[6.2.2.02,7]dodec‐2(7)‐en‐4 yl methyl ketone)]iron) whose

ISSN:0018-019X    

DOI:10.1002/hlca.19870700502

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractA method is described for the preparation of (+)‐(R)‐methyl hydrogen 2‐(tert‐butoxymethyl)‐2‐methyl‐malonate (5e) in synthetically useful amounts from readily available star

ISSN:0018-019X    

DOI:10.1002/hlca.19870700503

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractDiels‐AlderReactions of 2,4‐Bis{[(tert‐Butyl)dimethylsilyl]oxy}‐3‐aza‐‐1,3‐pentadien with HeterodienophilesThe 2,4‐bis{[(tert‐butyl)dimethylsilyl]oxy}‐3‐aza‐1,3‐pentadien(2) reactsviatheDiels‐Alderadducts3,6a‐c, and8a,b, which cannot be isolated, giving the triazines4,7a‐c, and the oxadiazines9a,b. The hydrolysis of4in MeOH affords theN‐acetyl‐acetamid derivative5. The formula of9ais

ISSN:0018-019X    

DOI:10.1002/hlca.19870700504

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe 4‐hydrazinobenzyl alcohol (3was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4‐hydrazinobenzoate (4), whereas LiA1H4or LiBh4reduction of4proceeded further to yield (viaintermediate3) (4‐tolyl)hydrazine (5). The alcohol3was stable under O2‐free conditions and exhibited no tendency to eliminate H2O, neither thermally nor with H+catalysis. Oxidation of3with SeO2yielded 4‐(hydroxymethyl)benzine‐diazonium ion (8), identified by its azo coupling product9with 2‐naphthol. Condensation of3with 1‐benzyl 5‐HydrogenN‐(benzyloxycarbonyl)‐L‐glutamate (10) in presence of dicyclohexylcarbodiimide afforded 81% of N2‐(benzyloxycarbonyl)‐L‐ glutamic acid 1‐(benzyl‐ester) 5‐{2‐[4‐(hydroxymethyl)phenyl]hydrazide} (11) which upon controlled hydrogenolysis (quinoline‐sulfur‐poisoned Pd/C catalyst) gave 82% of L‐Glutamic acid 5‐{2‐[4‐(hydroxymethyl)phenyl] hydrazide} (1), i. e. agaritine, a metabolite ofAgaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of (11) yi

ISSN:0018-019X    

DOI:10.1002/hlca.19870700505

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe thermodynamic effects of the nucleotide coordination on the Co‐C bond strengths in theB12coenzymes were analyzed. Methyl group transfer reactions from methylcob(III)inamides to cob(II)inamides and cob(I)inamides in neutral aqueous solution were used in equilibration experiments to determine the effect fo the intramolecular coordination of the nucleotide function on the Co‐C bond dissociation energies of methylcob(III)alamin (4). In the equilibrium between4, cob(I)inamide (11), cob(I)alamin (10) and methylcob(III)inamide6(Scheme 2),4and11were found to predominate (4+11⇆10+6, equilibrium constantKI/III≈0.004), while the equilibrium between4, cob(II)inamide9, cob(II)alamin (5), and6(Scheme 1) proved to be well balanced (4+9⇄5+6, equilibrium constantKII/III=0.60). These equilibrium values indicate the nucleotide coordination to stabilize the Co–C bond in4both against homolysis (slight effect) and against nucleophilic heterolysis (considerable effect). They reflect a stabilization of the complete corrins4and5by the nucleotide coordination, which is also indicated for4and5by their (nucleotide) basicity. The latter information, where available for other organocobalamins, allows the analysis of the thermodynamicnucleotidetranseffect there as well: e.g. in coenzymeB12(1), the nucleotide coordination is found this way to weaken the Co–C bond towards homolysis byca

ISSN:0018-019X    

DOI:10.1002/hlca.19870700506

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Synthesis of (–)‐(1R,2S)‐Norephedrine HomologuesThe amino function of esters of some simple natural amino acidsIis blocked in the form of a cyanoenamine by means of 2‐oxocyclopentanecarbonitrile, so that the corresponding cyanoenamino estersIIare obtained. The reaction of a disubstituted lithium amide withIIleeds to the cyanoenamino‐amidesVI. The amide function present inVIis then transformed into an aromatic ketone by means of phenyllithium, to give the (benzoylalkyl)aminocyclopentenecarbonitrilesVII. Reduction of CompoundsVIIwith NaBH4in EtOH −80° affects only the keto function and leads to the [(α‐hydroxybenzyl)alkyl]amino‐cyclopentenecarbonitrilesVIII. The amino function is then deprotected by acid hydrolysis to give the amino‐alcoholsIXwith yields close to 50%; in every amino‐alcoholIX, theerythroisomer, homologous to natural (–)‐(1R,2S)‐norephedrine is the more abundant or the single product. All the polyfunctional compounds prepared conserve optical activity; it has been demonstrated that the amino‐alcoholsIXare pure enantiomers and that no racemisation lakes place a

ISSN:0018-019X    

DOI:10.1002/hlca.19870700507

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractA new, versatile phosphorylating agent, bis[2‐(p‐nitrophenyl)ethyl] phosphorochloridate (3), has been prepared and is used for 3′‐ and/or 5′‐phosphorylations of nucleosides. The resulting bis[2‐(p‐nitrophenyl)ethyl] phosphotriesters are versatile synthons in oligonucleotide synthesis leading finally to 3′‐ and/or 5′‐terminated monophospha

ISSN:0018-019X    

DOI:10.1002/hlca.19870700508

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractReaction of the tricyclic psychotropic drug opipramol (1) with an excess of HNO2affords a product mixture mutagenic forSalmonella typhimurium. The main product is a tetracyclic furoxan2(yieldca.80%), resulting from nitrosation at C(10) and C(11) of1. Compound2is not mutagenic. The essential mutagen is a nitroarene3formedviacontraction of the central ring of1, and nitrosation at C(2). Its yield is extremely low (<0.1%). Nitroarenes have previously not been encountered as mutagenic products of the interaction of drugs with nitrite.

ISSN:0018-019X    

DOI:10.1002/hlca.19870700509

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractA 6‐step synthesis of (±)‐grandisol (1) is presented, which involves dichloroketene addition to 3‐methyl‐3‐butenyl acetate (4), reductive dechlorination of the adduct6to the ketone7and saponification to8, aldolization of7or8with acetone and cyclization to the bicyclic ketone9,Wolff‐kishner, reduction to14, and finally ring opening to1.Since9is a known intermediate of the synthesis of (±)‐lineatin (2), the latter can now be obta

ISSN:0018-019X    

DOI:10.1002/hlca.19870700510

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Synthesis of 3‐(2‐Carboxy‐4‐pyridyl)‐and 3‐(6‐Carboxy‐3‐pyridyl)‐DL‐alanineAs starting materials for potential photochemical approaches to betalaines C(R = COOH) and to muscaflavine F(R = COOH), β‐(2‐carboxy‐4‐pyridyl)‐ and β‐(6(carboxy‐3‐pyridyl))‐DL‐alanine (AandDwithR= COOH or4and11), respectively, were prepared (Scheme 1). The synthesis of4(= A, R = COOH) started with the 2‐[(4‐pyridyl)methyl]malonate1and proceededviatheN‐oxide2, cyanation and hydrolysis (Scheme 2). Amino acid11was obtained from (3‐pyridyl)methyl‐bromide (6)viathe malo

ISSN:0018-019X    

DOI:10.1002/hlca.19870700511

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY