摘要:

Enantioselective Saponification of Diacetates of 2‐Nitro‐1,3‐propanediols by Pig‐Liver Esterase and Preparation of Enantiomerically Pure Derivatives of 2‐Nitro‐allylic Alcohols (Chiral Multiple‐Coupling Reagents)The reproducible enantioselective saponification of open‐chain and cyclic diacetates ofmeso‐2‐nitro‐1,3‐propanediols (see4b–13b) with pig‐liver esterase (PLE) gives monoacetates (see4c–l3c) of>95% enantiomeric excess. TheReenantiotopic acetate group appears to be saponified preferentially, as proved by the X‐ray crystal structure analysis of three camphanoates4d,6d, and7d. Elimination of H2O or AcOH from the hydroxy acetates thus available gives derivatives of nitro‐allylic alcohols (see20–24,27, and29) which are subjected to diastereoselectiveMi

ISSN:0018-019X    

DOI:10.1002/hlca.19880710102

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Stereoisomeric Sinensiaxanthins and Sinensiachromes: Separation and Absolute ConfigurationThe so‐called sinensiaxanthins and sinensiachromes, important apocarotenols from various fruits, have been separated into 2 and 4 stereoisomers, respectively, and their absolute configurations have been determined: (3S,5R,6S)‐5,6‐epoxy‐5,6‐dihydro‐10′‐apo‐β‐carotene‐3,10′‐diol (2), its (9Z)‐stereoisomer 7, the (8R)‐ and (8S)‐epimers of (3S, 5R)‐5,8‐epoxy‐5,8‐dihydro‐ 10′ ‐apo‐β‐carotene‐3, 10′‐diol (4and5), and their (9Z)‐stereoisomers3and probably6.Thus, sinensiaxanthins are cleavage products from (Z/E)‐isomeric antheraxanthins or violaxanthins (scission at C(9′)–C(10′))

ISSN:0018-019X    

DOI:10.1002/hlca.19880710103

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe 5,6:5′,6′‐diepoxy‐5,6:5′,6;‐tetrahydro‐β,β‐carotene, isolated from tubers of a white‐fleshed variety of sweet potato (Ipomoea batatasLAM.) has been assigned the (5R,6S,5′R,6′S)‐chirality on the basis of its

ISSN:0018-019X    

DOI:10.1002/hlca.19880710104

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Halochromic Molecules. Synthesis and Acidobasic Properties of Substituted HeteroarenoquinazolinesWe have synthetized a series of substituted heteroarenoquinazolines. The 90‐MHz FT1H‐NMR spectra of starting and final products supported the postulated structures. Fragmentation in the mass spectra also were consistant with the assumed structures. With acid, the compounds partly from ring‐opened, intensely coloured triphenylcarbenium salts of the Rhoduline‐R type (C. I. 42565). UV/VIS spectra of the salts are discussed on the basis of VEPPP‐CI calculations. The ϵpH*curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex protonation

ISSN:0018-019X    

DOI:10.1002/hlca.19880710105

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe ‘syn’‐1,3‐diols3,4and5with a C7, C6, and C5chain, respectively, were synthesized from methyl hydrogen 3‐hydroxyglutarate (2;Schemes 1and2). The latter is available in (R)‐ and (S)‐configuration. Octyl (3R)‐4‐chloro‐3‐hydroxybutanoate (17) is an alternative starting material for the preparation of5(Scheme 3.) The epoxide20, derived from5in a one‐pot reaction, is a versatile synthon, which selectively reacts with a great number of

ISSN:0018-019X    

DOI:10.1002/hlca.19880710106

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe novel metabolite dendryphiellin A ( = (+)‐(1R,2S,8aR)‐ 1,2,6,7,8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6R*, 2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoate; (+)‐1) is isolated from cultures of the marine deuteromyceteDendryphiella salina. There is no precedent in fungi for trinor‐eremophilanes or for branched C9carboxylic acids, the two classes of compounds constituting (+)‐1. The structure is secured by NMR spectroscopy and hydrolysis of (+)‐1 to give the side‐chain moiety ((6R*,2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoic acid (2)) intact, whilst the trinor‐ermophilane moiety is decomposed. The absolute configuration at the trinor‐eremophilane moiety is established from exciton

ISSN:0018-019X    

DOI:10.1002/hlca.19880710107

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractTwo novel pregnatrienolones isolated in very small amounts from the North‐East‐Atlantic demospongeAxinella agnata(Tetractinomorpha, Axinellida) are unique in having C(2)C(3) (or C(3)C(4)), C(7)C(8), and C(16)C(17) bonds and a 12β‐OH group which, being strongly H‐bonded to a 20‐keto group, resists acylation.1H‐ and13C‐NMR spectroscopy of the steroids and of products of their selective epoxidation or reduction allow us to propose the structures (+)‐12β‐hydroxy‐5α‐pregna‐2,7,16‐trien‐20‐one ( = agnatasterone A, (+)‐1), and (+)‐12β‐hydroxy‐5α‐pregna‐3,7,16‐trien‐20‐one ( = agnatasterone B. (+)‐5),

ISSN:0018-019X    

DOI:10.1002/hlca.19880710108

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractFour new pterocarpinoids, sphenostylin A, B, C, and D (1–4), have been isolated from the CHCl3extract of the root bark ofDolichos marginatassp.erecta(Leguminosae) by preparative liquid chromatography. The structures have been established by spectroscopic methods (UV,1H‐NMR,13C‐NMR, EI‐MS, DCI‐MS, CD) and chemical transformations. The isolated compounds showed weak antifungal activity againstCladosporium cu

ISSN:0018-019X    

DOI:10.1002/hlca.19880710109

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractHomophthalic acid (1) undergoes reaction with 1,2‐, 1,3‐, and 1,4‐diamines to give condensed 1(2H)‐isoquinolinones like2,4,13, and25, which exhibit marked enamine character. These are attacked by electrophiles at the N or C terminus. Some notable reactions of imidazoisoquinolone2are those with maleic and acrylic acids to form the tetracycles48and51, respectively. With propiolic acid,5underwent an interesting reaction to form the benzimidazonaphthyridine53. An equally interesting behaviour was elicited from2in its reaction with formaldehyde, when in addition to the expected methylene‐bridged molecule59, the novel spiro derivative60was formed by the dimerisation of a presumed azadiene inter

ISSN:0018-019X    

DOI:10.1002/hlca.19880710110

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractA study of photo‐induced electron‐transfer reactions in MeCN with 9,10‐dicyanoanthracene as acceptor and 21 electron donors with transient photoconductivity measurements is reported. The free‐ion yield and the rate constant of back electron transfer are determined. For exergonic reactions, the ‘Marcus‐inverted’ region is observed. The fit with the theory is best, when a nearly solvent‐independentCoulombterm is used in the calculation of the

ISSN:0018-019X    

DOI:10.1002/hlca.19880710111

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY