摘要:

AbstractThe origin of the carbon skeleton of verrucarin E(1)from acetate as precursor is confirmed. Incorporation studies with [1,2‐13C]‐acetate have demonstrated that two acetoacetate units couple together as shown in patternA(Scheme 2)and not as inB. Analysis of the deuterium distribution in both verrucarin E(1)isolated after the incorporation of [2‐13C,2‐2H3]‐acetate and in sodium acetate obtained afterKuhn‐Rothoxidation of the metabolite demonstrated that C(7) is derived from the starter unit of one of the acetoacetate moieties. The deuterium exchange in verrucarin E(1)occurring during fermentation was i

ISSN:0018-019X    

DOI:10.1002/hlca.19800630402

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Stereospecific 1,2‐Migration of Hydroxyl, Aryl and Alkyl Groups during the Nitrosation of Amino Acids in Hydrogenfluoride/Pyridine Vorläufige MitteilungThe nitrosation of α‐amino acids in hydrogenfluoride/pyridine was reinvestigated. In contrast to recent reports [1] [2]it was found that this reaction takes place either with entire (phenylalanine, tyrosine, threonine) or partial (valine, isoleucine) rearrangement to yield β‐fluorocarboxylic acids. Glycine, alanine and α‐aminobutanoic acid were converted exclusively into the α‐fluorocarboxylic acids. The substitution of the amino group takes place with stereochemical retention as revealed by NMR. examination of the 2‐fluoro‐3‐methylpentanoic acids obtained fromL‐isoleucine andD‐allo

ISSN:0018-019X    

DOI:10.1002/hlca.19800630403

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe photochemical synthesis of the title complex from 1,3‐butadiene and dodecacarbonyltriosmium is described. The1H‐NMR. and H‐coupled13C‐NMR. spectra are analyzed completely and the H, H‐ and C,H‐coupling constants compared with the data of the corresponding Fe‐ and Ru‐complexes. One‐bond13C,13C‐coupling constants are reported for a series of complexed 1,3‐dienes. All data are consistent with an increasing distortion from planarity of the C,H‐skeleton at the terminal diene C‐atoms in

ISSN:0018-019X    

DOI:10.1002/hlca.19800630404

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe pK α*of 11 triarylmethylamines (tritylamines), eight of which are new, and some related bases were measured in methylcellosolve/water 80:20 (MCS); some were also measured in dioxane/water 60:40 (Dx), acetonitrile (An), nitrobenzene (Nb) and acetic acid (Ac). (1) The influence of the aryl groups on the basicity is essentially additive; (2) In different solvents, similar linear free energy relationships were found, with differences inp* characteristic of solvation; (3) The influence on basicity of substituents of the aryl groups followsHammett's relationship. These results indicate a preponderance of inductive effects.N, N‐Dimethyltritylamine(3b)(pK aMCS=3.40) shows a marked crowding effect, absent in the isomeric tertiary amines13and14. Tri‐p‐nitrotritylamine(10a)(pK aMCS=3.10),N, N‐dimethyl‐tri‐p‐nitrotritylamine(10b)(pK aAc=0.50), and3bare particularly weak bases; the base‐weakening effect of the trinitrotrityl group is similar to that of the cyanomethyl a

ISSN:0018-019X    

DOI:10.1002/hlca.19800630405

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractIrradiation of the dienone methyl ether3afurnished the unstable regioisomeric photoadducts4aand5awhich onLewisacid‐catalyzed fragmentation afforded the tricyclic diketones6,7and8. The same mixture was obtained from the isobutyl ether3b(Scheme 2

ISSN:0018-019X    

DOI:10.1002/hlca.19800630406

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Bis‐indolic Alkaloids ofCatharanthus ovalisVindolicine and fourteen bis‐indolic alkaloids of the vinblastine group have been isolated from the aerial parts ofCatharanthus ovalisMGF. Three of them: vincovaline, vincovalinine and vincovalicine had not been previously isolated from aCatharanthusspec

ISSN:0018-019X    

DOI:10.1002/hlca.19800630407

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

The Synthesis of 6exo‐Substituted 2exo‐Norbornylp‐ToluenesulfonatesA number of hitherto unknown 6exo‐substituted 2exo‐norbornanols and theirp‐toluenesulfonates have been prepared by functionalization of intermediate

ISSN:0018-019X    

DOI:10.1002/hlca.19800630408

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

The synthesis of 6exo‐Substituted 2endo‐Norbornylp‐ToluenesulfonatesThe preparation of hitherto unknownp‐toluenesulfonates of 6exo‐substituted 2endo‐norbornanols i

ISSN:0018-019X    

DOI:10.1002/hlca.19800630409

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractL‐Cα‐t‐Butylglycine (Bug), its amide, methyl ester, andNα‐t‐butoxycarbonyl derivative were prepared by an asymmetric synthesis, and theHanschside‐chain hydrophobic (lipophilicity) parameter determined. A new enkephalin analogue, H · Tyr‐D‐Ala‐Gly‐Phe‐Bug · NH2was synthesized which is pharmacologically active in twoin vitroassays and strongly resistant against a

ISSN:0018-019X    

DOI:10.1002/hlca.19800630410

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractReaction of the 1‐substituted‐3‐cyano‐isothioureas6with hydroxylamine gave mixtures of the 5‐amino‐3‐substituted‐amino‐1,2,4‐oxadiazoles1and the isomeric 3‐amino‐5‐substituted‐amino‐1,2,4‐oxadiazoles8in which1usually predominated. The structural assignment of these products is discussed. In a second method, the 2‐hydroxy‐1‐methyl‐1‐phenyl‐guanidine15was converted to the corresponding 3‐disubstituted‐amino‐5‐trichloromethyl‐1,2,4‐oxadiazole16, a precursor to the 5‐amino derivatives17

ISSN:0018-019X    

DOI:10.1002/hlca.19800630411

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY