Substrate specificity and enantioselectivity of nitrile hydratase and amidase from R. rhodochrous IFO 15564 has been studied by applying a series of α,α-disubstituted malononitriles and related substrates. The amidase preferentially hydrolyzed the pro-(R) carbamyl group (amide) of the prochiral diamides, an intermediate resulting from the action of nitrile hydratase in a non-enantiotopic group-selective manner. The introduction of a fluorine atom at the α-position caused an inhibitory effect on amidase. By a combination of this microbial transformation and the subsequent Hofmann rearrangement, an important precursor of (S)-methyldopa with 98.4% ee has been prepared. For the enzymatically poor substrate, the action on HO3SONO-H2O on the carbamyl group was effective, leaving the cyano group intact. This conversion is demonstrated as the key step for the expeditious preparation of (±)-α-cyano-α-fluoro-α-phenylacetic acid (CFPA) from diethyl α-fluoro-α-phenylmalonate.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry