Stereoselective acyclic synthesis via allylmetals: vicinal diols from γ-alkoxyallylaluminium compounds and aldehydes or ketones
作者:Masato Koreeda、Yoshio Tanaka
DOI:10.1039/c39820000845
日期:——
The reaction of in situ generated γ-alkoxyallylaluminiumcompounds with aldehydes or ketones at –78 °C leads to the highly diastereoselective formation of mono-protected vicinaldiols; the precursor to exo-brevicomin was efficiently synthesised using this method.
Horseradish Peroxidase-Catalyzed Enantioselective Reduction of Racemic Hydroperoxy Homoallylic Alcohols: A Novel Enzymatic Method for the Preparation of Optically Active, Unsaturated Diols and Hydroperoxy Alcohols
作者:Waldemar Adam、Michael Lazarus、Ute Hoch、Marion N. Korb、Chantu R. Saha-Möller、Peter Schreier
DOI:10.1021/jo980028h
日期:1998.9.1
The kinetic resolution of chiral diastereomeric hydroperoxy homoallylic alcohols 1 by horseradish peroxidase-catalyzed asymmetricreduction affords the opticallyactive (R,R) or (R,S) allylic diols 2 and (S,S) or (S,R) hydroperoxy homoallylic alcohols 1 in high enantiomeric excess (up to 99%).
3-Bromozinc Propenyl Esters: An Experimental and Theoretical Study of the Unique Stereocrossover Observed in Their Addition to Aromatic and Aliphatic Aldehydes
作者:A. Bottoni、M. Lombardo、G. P. Miscione、J. B. Pujol Algué、C. Trombini
DOI:10.1021/jo701661z
日期:2008.1.1
[GRAPHICS]We report the results of a combined experimental and theoretical study on the reaction of 3-bromopropenyl acetate in the presence of zinc with three different aldehydes (i.e., benzaldehyde, 2-methylpropanal, and cyclohexanecarboxaldehyde). A 80% de in favor of the anti product has been experimentally observed. with both saturated aldehydes, while for benzaldehyde, a 1:1 synlanti ratio has been found. DFT computations show the existence of three eta(1)-allylic organozinc complexes [gamma-(Z)-5a, gamma-(E)-5a, and alpha-5a], very close in energy. Only gamma-(Z)-5a and gamma-(E)-5a lead to the observed product. The computational investigation of the reaction of these allylic organozinc complexes with benzaldehyde and 2-methylpropanal demonstrates in both cases the existence of two competitive reaction paths leading to the syn and anti adducts, respectively. An anti preference has been found for 2-methylpropanal with both gamma-(Z)-5a and gamma-(E)-5a species (a diastereoselectivity larger than 80% is predicted), in agreement with the experiment. With benzaldehyde, while the reaction of gamma-(Z)-5a retains an anti-stereopreference (de = 70%), that involving gamma-(E)-5a is characterized by two degenerate transition states. In this case, the agreement between computations and experiments would be satisfactory under the assumption that the initial oxidative addition affords the gamma-(E)-5a zinc complex only. Additional MP2 computations have demonstrated that pi-stacking interactions can play a significant role in determining the relative energy of the transition states leading to the syn and anti products.
Horseradish peroxidase (HRP)-catalysed enantioselective reduction of racemic hydroperoxy homoallylic alcohols: a novel enzymatic method for the preparation of optically active, unsaturated diols and hydroperoxy alcohols
作者:Waldemar Adam、Ute Hoch、Hans-Ulrich Humpf、Chantu R. Saha-Möller、Peter Schreier
DOI:10.1039/cc9960002701
日期:——
The kinetic resolution of chiral diastereoisomeric hydroperoxy homoallylic alcohols by horseradish peroxidase (HRP)-catalysed asymmetric reduction affords the optically active (R,R) or (R,S) allylic diols and (S,S) or (S,R) hydroperoxy homoallylic alcohols in high enantiomeric excess (up to 99%).
Studies on the sharpless asymmetric epoxidation of unsymmetrical divinylmethanols
作者:Toshio Honda、Hirotake Mizutani、Kazuo Kanai
DOI:10.1039/p19960001729
日期:——
A reaction of racemic unsymmetrical divinylmethanol rac-13 under the Sharpless asymmetric epoxidation conditions using stoichiometric amounts of titanium tetraisopropoxide [Ti(OPi)4], D-(–)-diisopropyl tartrate (DIPT) and tert-butyl hydroperoxide (TBHP) afforded R-14 and R-15 in 41 and 43% yield, each with > 99%ee, respectively, where the kinetic resolution and subsequent epoxidation had proceeded