Enzymatic synthesis and subsequent racemization rates determination of optically active D-5-phenylhydantoin and D-5-hydroxylphenylhydantoin

A process using immobilized D-hydantoinase for the preparation of optically active hydantoins was developed At basic pH; die racemic hydantoin was hydrolyzed into D-N-carbamoyl-amino acid. The equilibrium constant of the hydrolysis reaction increased with pH. At acidic pH, the D-N-carbamoyl-amino acid was favorably converted to D-hydantoin. Optically active D-phenylhydantoin (D-PH) and D-p hydi hydroxyphenylhydantoin (D-pHPH) were prepared directly from the racemic hydantoins D,L-PH and D,L-pHPH, respectively via corresponding D-N-carbamoylamino acid in one pbt reaction just by adjusting the reaction pH from 8.5 to 5.5. The D-PH and D-pHPH obtained in this mild enzymatic reaction were nearly optically uniform. The racemization rate of these hydantoins increased with pH and temperature. It was more strongly affected at basic than acidic pH. The racemization rate of pHPH was slightly higher than that of PH. (C) 1999 Elsevier Science Inc. All rights reserved.