The effect of catechin derivatives on the enantioselectivity of lipase-catalyzed hydrolyses of alkynol benzoate esters
摘要:
Polyphenols. such as (+)-catechin and pyrogallol could be used to enhance stereochemical control in the lipase-catalyzed hydrolysis of alkynol benzoate esters, leading to increased enantioselectivities in the kinetic resolution of alkynols with lipase, Amano AH. (C) 2002 Elsevier Science Ltd. All rights reserved.
An expedient method for the stereoselective preparation of alk-2-yne-1,4-diols has been achieved, based on the addition of chiral alk-1-yn-3-ols (or their protected derivatives) to aldehydes mediated by zinc triflate, Et3N, and (+)- or (–)-N-methylephedrine. In general, the configuration observed at the emergent stereocenter depends on the N-methylephedrine employed resulting in good to excellent
An efficient approach to alk-4-yne-l,2,3,6-tetraols is described by stereoselective addition of terminal 2-alkyn-1-yl esters to Ley's butane-2,3-diacetal-protected glyceraldehyde. The application of this methodology to a convenient synthesis of (-)-polyoxamic acid derivative is disclosed herein.
Ruthenium Hydride-Promoted Dienyl Isomerization: Access to Highly Substituted 1,3-Dienes
作者:Joseph R. Clark、Justin R. Griffiths、Steven T. Diver
DOI:10.1021/ja4011207
日期:2013.3.6
Ruthenium hydrides were found to promote the positional isomerization of 1,3-dienes into more highly substituted 1,3-dienes in a stereoconvergent manner. The reaction can be conducted in one pot starting with terminal alkynes and alkenes by triggering decomposition of the Grubbs catalyst into a ruthenium hydride, which promotes the dienyl isomerization. The presence of an alcohol additive plays a helpful role in the reaction, significantly increasing the chemical yields. Mechanistic studies are consistent with hydrometalation of the geminally substituted alkene of the 1,3-diene and transit of the ruthenium atom across the diene framework via a pi-allylruthenium intermediate.