摘要:

The title saponin, 28-O-δ-D-galactopyranoside of oleanolic acid, was prepared stereo- and regio-selectively from oleanolic acid and phenyl β-galactoside, by enzymatic transgalactosidation catalysed by β-galactosidase [EC 3.2.1.23] fromEscherichia coliin an organic solvent at pH 5 and 22°C.

ISSN:1057-5634    

DOI:10.1080/10575639408044917

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Bark ofOcotea foetens, a lauraceous tree from Madeira Island, is shown tootainmyristicinand3˝,5′-dimethoxy-4˝,5˝-methylenedioxy-l,2,3,4-dibenzo–1to contain myrisistcin and 3˝,5′-dimethoxy-4˝,5˝-methylenedioxy-1,2,3,4-dibenzo-1,3,5-cycloheptatriene. The bridged biphenyl system of the latter is shown to enantiomerize with a ΔG‡ = 15.4 kcal/mol.

ISSN:1057-5634    

DOI:10.1080/10575639408044918

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

From the roots of Taxus baccata, two new taxane derivatives, taxa-4(20),11-diene-10β-methoxy-2α,5α-diacetoxy-14β,α-methylbutyrate (1) and taxa-4(20-),11-diene-5α-hydroxy-1β, 7β,9α, 10β-tetraacetate (2) were obtained together with the known diterpenoids taxusin (3) 7β-acetoxytaxusin (4) and 2-deacetoxytaxinin J (5). In addition to these diterpenoids, a compound previously identified as taxa-4 (20), 11-diene, 5α,7β,10β-triacetoxy-2α,α-methylbutyrate was isolated and its structure has been revised as taxa-4(20), 11-diene-2α,5α,10β-triacetoxy-14β, α-methylbutyrate (6).

ISSN:1057-5634    

DOI:10.1080/10575639408044919

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The action of sulfur monochloride on aryltert-butyl disulfides in tetrahydrofuran led directly to benzopentathiepins in good yields. The reaction was applied to the synthesis of two benzopentathiepins10aand10b, varacin1and isolissoclinotoxin A2aderivatives.

ISSN:1057-5634    

DOI:10.1080/10575639408044920

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The synthesis of two natural 1,3,5-triacylbenzenes is reported. Both compounds have previously been isolated from West African medicinal plants (Cochlospermum planchonii, C. angolense and C. tinctorium).

ISSN:1057-5634    

DOI:10.1080/10575639408044921

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

From the inner bark of a specimen ofMyracrodruon urundeuvawere isolated the new chalcone dimers1and2, named urundeuvina A and B, as methyl ether derivatives (1aand2a) obtained by methylation with diazomethane. The structure elucidation of these derivatives involved spectral data analysis, including 2D NMR experiments and NOE difference spectra.

ISSN:1057-5634    

DOI:10.1080/10575639408044922

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The QSAR of a series of 21 nicotinic agonists, anatoxin-a (AnTX) and derivatives, was investigated using multivariate statistical techniques. Physicochemical properties were calculated for the compounds using computational chemistry. In order to model the structures it was necessary to choose a common conformation. This was achieved by comparison of the structure of AnTX to that of (-)-cytisine, a rigid potent nicotinic agonist. The final data set of 32 molecular descriptors was examined using principal components analysis and non-linear mapping. Examination of the plots produced by these techniques demonstrated significant clustering of both chemical and activity classes. The inclusion of 6 test compounds to these models resulted in satisfactory predictions of their activity for 5 of these compounds.

ISSN:1057-5634    

DOI:10.1080/10575639408044923

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Hasakol, an inhibitor against Ba++-induced contraction of smooth muscles, has been synthesized in six steps starting from 7-O-geranylumbelliferoneviaan improved Claisen rearrangement.

ISSN:1057-5634    

DOI:10.1080/10575639408044924

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The reaction of perezone1with 3,4,5,6-tetrahydro-2-pyrimidinethiol11promotes a 1,2-carbonyl transposition in the quinoid ring of1giving rise to isoperezone8, which treated with BF3·Et2O produces dihydroisoperezinone9.

ISSN:1057-5634    

DOI:10.1080/10575639408044925

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The reductive elimination-amination of2(a, b)in the presence of amines3 (a, b)under ultrasound irradiation provides pyrrolidines5 (a,b,g,h)in excellent yield.

ISSN:1057-5634    

DOI:10.1080/10575639408044926

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor