Process for preparing optically active hydantoins

摘要

A process for preparing optically active hydantoins having the general formula (II): <IMAGE> (II) wherein R1 and R2, which are different from each other, are independently alkyl group, aralkyl group, aryl group, substituted alkyl group, substituted aralkyl group, or substituted aryl group, or R1 and R2 form an asymmetric cyclic compound, characterized in that one configuration of racemic N-carbamoyl- alpha -amino acid having the general formula (I): <IMAGE> (I) wherein R1 and R2 are as above, is enzymatically converted into the corresponding hydantoins. The present invention provides a process for an optical resolution with a high efficiency which can be used for the synthesis of (S)-6-fluoro-spiro-[chroman-4,4'-imidazolidine]-2',5'-dione (USAN; Sorbinil), which is an optically active hydrantoins attracting public attention as a preventive or a remedy for the particular chronic symptoms of diabetes such as cataract and neuropathy, and (S)- alpha -methyl-3,4-dihydroxyphenylalanine (L-methyldopa), which is an optically active amino acid widely used as antihypertensives. Further, the present invention provides a novel finding that N-carbamoyl- alpha -amino acid having no hydrogen atom on its alpha -carbon atom can be biochemically converted into hydantoins by an enzymatic cyclization reaction.