Separative preparation of the four stereoisomers of β-methylphenylalanine with N-carbamoyl amino acid amidohydrolases

The selective preparation of the four stereoisomers of β-methylphenylalanine (Mphe) from mixtures of the four stereoisomers of N-carbamoyl-β-methylphenylalanine (NCMphe) with N-carbamoyl amino acid amidohydrolases (carbamoylases) was developed. d-Carbamoylase specifically hydrolyzed threo-d-NCMphe with a little side activity toward erythro-d-NCMphe, thus threo-d-Mphe was produced with high optical purity from a mixture of the four stereoisomers of NCMphe. l-Carbamoylase specifically produced threo-l-Mphe from a mixture of the four stereoisomers of NCMphe. The erythro-d-Mphe was obtained from erythro-dl-NCMphe which was prepared through diastereomer resolution by separative crystallization of benzoyl Mphe with a little side activity of d-carbamoylase toward erythro-d-NCMphe and the remaining erythro-l-NCMphe was chemically hydrolyzed to erythro-l-Mphe.