The addition of acyl cyanides to prochiral aldehydes catalyzed by a chiral Lewis acid and an achiral Lewis base produces highly enantioenriched O-acylated cyanohydrins. alpha-Keto esters undergo the same type of addition, although via a different mechanism in which the enantioselectivity originates from a chiral Lewis base. In the presence of a biocatalyst, the minor, undesired enantiomer obtained in the reactions with aldehydes can be selectively hydrolyzed to re-form the starting aldehyde, permitting the reaction to be run in a cyclic manner. The minor-enantiomer recycling results in an essentially enantiopure product. Selective enzymatic hydrolysis is also a key step in high-throughput analysis of conversions and enantiomeric ratios.
2010. no 3, 355-367 p.