Asymmetric Aerobic Oxidation of α-Hydroxy Acid Derivatives Catalyzed by Reusable, Polystyrene-Supported Chiral N-Salicylidene Oxidovanadium tert-Leucinates
作者:Santosh B. Salunke、N.Seshu Babu、Chien-Tien Chen
DOI:10.1002/adsc.201100062
日期:2011.5
The direct immobilization of two different C‐5‐propargyl ether‐modified, chiral N‐salicylidene vanadyl(V) tert‐leucinates onto 4‐azidomethyl‐substituted polystyrene by clickchemistry was examined. Among the eight different solvents investigated, the resulting polystyrene‐supported catalysts promote the asymmetric, aerobic oxidation of α‐hydroxy (thio)esters and amides with enantioselectivities of
Biocatalytic reduction of α-keto amides to (R)-α-hydroxy amides using Candida parapsilosis ATCC 7330
作者:Selvaraj Stella、Anju Chadha
DOI:10.1016/j.cattod.2012.03.081
日期:2012.12
Biocatalytic reduction of primary and secondary alpha-keto amides was accomplished using whole cells of Candida parapsilosis ATCC 7330. The primary (R)-alpha-hydroxy amides were obtained in good enantiomeric excess (up to 94%) and conversion (88-99%) as compared to the secondary (R)-alpha-hydroxy amides. (C) 2012 Elsevier B.V. All rights reserved.
[GRAPHIC]Hundreds of Lewis acid/ligand combinations have been screened for stereochemical induction in the Passerini multicomponent reaction. The combination of titan tetraisopropylate and (4S,5S)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyidioxolane was found to give enantiomeric excesses between 32% and 42% in several examples. The absolute stereo induction of one example was determined chemically and by means of X-ray crystallography. This comprises the first asymmetric Passerini reaction and the first example of a stereochernical induction in an isocyanide based multicomponent reaction by a chiral Lewis acid.