Enantioselective synthesis of α-thiocarboxylic acids via nitrilase biocatalysed dynamic kinetic resolution of α-thionitriles.

The enantioselective synthesis of alpha-thiocarboxylic acids by biocatalytic dynamic kinetic resolution (DKR) of nitrile precursors exploiting nitrilase enzymes is described. A panel of 35 nitrilase biocatalysts were screened and enzymes Nit27 and Nit34 were found to catalyse the DKR of racemic alpha-thionitriles under mild conditions, affording the corresponding carboxylic acids with high conversions and good-to-excellentee. The ammonia produced in situ during the biocatalytic transformation favours the racemization of the nitrile enantiomers and, in turn, the DKR without the need of any external additive base.