Highly diastereoselective reduction of chiral β-ketosulphoxides under chelation control: application to the synthesis of (R)-(+)-n-hexadecano-1,5-lactone
作者:Hiroshi Kosugi、Hiroshi Konta、Hisashi Uda
DOI:10.1039/c39850000211
日期:——
The presence of zinc chloride in the reduction of chiralβ-ketosulphoxides with di-isobutylaluminium hydride effects high 1,3-asymmetric induction to give β-hydroxysulphoxides; this method can be successfully applied to the synthesis of optically pure 1,4- or 1,5-lactones.
It is shown that reductions of β-ketosulfoxides of identical chirality (R) at sulfur, lead to reduction products of opposite stereochemistry according to the reducing agent used. The high enantiomeric excesses obtained (80 to 100%) provide a general route to bothenantiomers of methylcarbinols from the corresponding esters.
A facile and efficient separation of mixtures of epimeric cc-sulfinyl alcohols 2:3 can be accomplished by selective lipase-catalyzed acylation with neat vinyl acetate. Pseudomonas cepacia and Candida rugosa lipase showed opposite epimer differentiation in the esterification. (C) 1999 Elsevier Science Ltd. All rights reserved.