Unexpected Cycloisomerizations of Nonclassical Carbocation Intermediates in Gold(I)-Catalyzed Homo-Rautenstrauch Cyclizations
摘要:
An unexpected gold(I)-catalyzed homo-Rautenstrauch rearrangement of 1-cyclopropyl propargylic esters to cyclohexenones is disclosed. This rearrangement represents new evidence for the recently discussed gold-stabilized non-classical carbocation character of intermediates in gold catalysis. A mechanistic study proved partial chirality transfer from optically active propargyl acetates.
A new NAD-dependent alcohol dehydrogenase with opposite facial selectivity useful for asymmetric reduction and cofactor regeneration
作者:Gwo-Jenn Shen、Yi-Fong Wang、Curt Bradshaw、Chi-Huey Wong
DOI:10.1039/c39900000677
日期:——
A newNAD-dependentalcoholdehydrogenase isolated from a Pseudomonas species catalysed the reduction of many acyclic ketones to optically active alcohols with very high enantioselectivity (90 to >98% enantiomeric excess); the stereochemical course of the reduction was determined to be the transfer of the pro-(R) hydrogen from NADH to the Si face of the carbonyl group, a process different from that
Preparation of Bicyclic 1,2,4-Trioxanes from γ,δ-Unsaturated Ketones
作者:Armando P. Ramirez、Andrew M. Thomas、K. A. Woerpel
DOI:10.1021/ol8022853
日期:2009.2.5
Treatment of γ,δ-unsaturated ketones with hydrogen peroxide and acid provides a rapid entry into the medicinally important 1,2,4-trioxanestructure. Alkene substitution that stabilizes carbocationic intermediates proved to be important for the success of this transformation.
Retinoic acid analogs. Synthesis and potential as cancer chemopreventive agents
作者:Marcia I. Dawson、Peter D. Hobbs、Karl Kuhlmann、Victor A. Fung、C. Tucker Helmes、Wan-Ru Chao
DOI:10.1021/jm00183a010
日期:1980.9
Analogues of retinoic acid have been synthesized as potentialchemopreventiveagents against epithelial cancer. Ethyl (E)-9-(2-norbornenyl)-3,7-dimethylnona-2,4,6,8-tetraenoate (9), (E)-3,7-dimethyl-9-(2-ethyl-6,6-dimethyl-1-cyclohexen-1-yl)nona-2,4,6,8-tetraenoic acid (25), and 2-(2'-methoxyethoxy)ethyl retinoate (26) displayed good activity in the inhibition of tumor promoter-induced mouse epidermal
[EN] SUBSTITUTED CYCLOPENTYL- AND CYCLOHEXYL-DERIVATIVES USEFUL FOR PERFUMERY<br/>[FR] DÉRIVÉS CYCLOPENTYLIQUES ET CYCLOHEXYLIQUES SUBSTITUÉS UTILES POUR LA PARFUMERIE
申请人:GIVAUDAN SA
公开号:WO2017097884A1
公开(公告)日:2017-06-15
The present invention refers to substituted cyclopentyl- and cyclohexyl-derivatives of formula (I) wherein n, R1, R2, R3, R4 and X have the same meaning as given in the description. The invention further refers to fragrance compositions and fragranced articles comprising them.
Synthesis of (Z,E)- and (Z,Z)-α-farnesenes and -homofarnesenes
作者:E. David Morgan、Lorna D. Thompson
DOI:10.1039/p19850000399
日期:——
The ant substance (Z,E)-α-farnesene and its isomer (Z,Z)-α-farnesene have been synthesized in an overall yield of 34% in six stages from methyl cyclopropyl ketone and 6-methylhept-5-en-2-one via a Wittig condensation. A mixture of the corresponding (Z,E)-α-homofarnesene of ants and its (Z,Z) isomer were prepared in much poorer yield by the same method and incompletely characterized. The isomeric identification