Sprouted green peas have been used for the first time as biocatalysts for enantioselective reduction of prochiral ketones. The reactions are highly enantioselective to furnish chiral alcohols in good yields. The sprouted peas as biocatalysts are a cheap and easy way for generating some interesting chiral alcohols. This process is efficient and convenient to produce chiral secondary alcohols in water.
Enzymatickineticresolution of (±)-hydroxytetrahydropyrans has been achieved for the first time by means of lipase-mediated transesterification to afford optically active (2S,4R)-tetrahydropyranyl acetates and (2R,4S)-tetrahydropyranols in excellent yields with high enantioselectivity. Absolute configurations of the tetrahydropyranyl acetates were assigned as (S) by chemical correlation.
Phosphomolybdic acid (H3PMo12O40, a heteropoly acid) is found to catalyze efficiently the Prins cyclization of homoallylic alcohols with aldehydes in water at room temperature to provide tetrahydropyran-4-ol derivatives in high yields with all cis-selectivity. Only cyclic ketones can give spirocyclic products. The use of phosphomolybdic acid in water makes this procedure simple, more convenient, cost-effective, and environmentally friendly.
Diastereoselective Synthesis of 2,4-Disubstituted Tetrahydropyranols and Ethers via a Prins-Type Cyclization Catalyzed by Scandium Triflate
作者:Wen-Chun Zhang、Chao-Jun Li
DOI:10.1016/s0040-4020(00)00152-6
日期:2000.4
The reaction of aldehydes with homoallylic alcohols catalyzed by scandium triflate gives rise to the formation of 2-substituted tetrahydropyran-4-ols and ethers in good overall yields and with ‘all-cis’ configurations and high diastereoselectivities. The stereochemistries of these products were assigned with the assistance of coupling constants and NOE. Factors affecting the reaction have been examined