beta-Carbon stereoselectivity of N-carbamoyl-D-alpha-amino acid amidohydrolase for alpha,beta-diastereomeric amino acids

N-Carbamoyl-D-alpha-amino acid amidohydrolase (D-carbamoylase) was found to distinguish stereochemistry not only at the cl-carbon but also at the beta -carbon of N-carbamoyl-D-alpha-amino acids. The enzyme selectively acted on one of the four stereoisomers of N-carbamoyl-alpha,beta-diastereomeric ami no acids. This simultaneous recognition of two chiral centers by D-carbamoy lase was useful for the fine stereoselective synthesis of alpha,beta-diaste reomeric amino acids such as threonine, isoleucine, 3,4-methylenedioxypheny lserine and beta-methylphenylalanine. The stereoselectivity for the beta-ca rbon was influenced by the pH of the reaction mixture and by the bulk of th e substituent at the beta-carbon.