Plant-mediated stereoselective biotransformation of phenylglyoxylic acid esters.

Enantioselective reduction of the carbonyl group of three phenylglyoxylic acid esters (methyl, ethyl, and n-propyl esters, 2-4) was conducted using blended plant materials (roots of carrot, beetroot, celeriac and parsley; apple). All used biocatalysts transformed these esters to the corresponding mandelic acid esters with high yield, preferably into the respective R-enantiomer. Butanedione addition improved the enantioselectivity of the reaction.