Asymmetric total synthesis of (+)-<i>exo</i>-brevicomin based on enantioconvergent biocatalytic hydrolysis of an alkene-functionalized 2,3-disubstituted epoxide

Abstract

A short total asymmetric synthesis of (+)-exo- and (–)-endo-brevicomin ((+)-exo-3 and (–)-endo-3), which are components of the attracting pheromone system of several bark-beetle species belonging to the genera Dendroctonus and Dryocoetes, was accomplished via a chemoenzymatic protocol. The key step consisted of biocatalytic hydrolysis by bacterial epoxide hydrolases of cis-configured 2,3-disubstituted oxiranes bearing olefinic side chains. This reaction proceeded in an enantioconvergent fashion, by affording a single enantiomeric vic-diol from the rac-epoxide in up to 92% ee and 83% isolated yield.Key words: bacterial epoxide hydrolase, 2,3-disubstituted oxirane, enantioconvergent hydrolysis, (+)-exo-brevicomin, (–)-endo-brevicomin.