ENZYMATIC ASYMMETRIC-SYNTHESIS OF ALPHA-AMINO-ACIDS - ENANTIOSELECTIVE CLEAVAGE OF 4-SUBSTITUTED OXAZOLIN-5-ONES AND THIAZOLIN-5-ONES

A general enzymatic asymmetric synthesis of L-alpha-amino acids has been developed. This method entails the use of the Pseudomonas cepacia lipase (P-30) to catalyze the enantioselective methanolysis of a variety of 4-substituted 2-phenyloxazolin-5-one derivatives in a nonpolar organic solvent to furnish optically-active N-benzoyl-L-alpha-amino acid methyl esters (ee = 66-98%), which in turn is subjected to a protease-catalyzed kinetic resolution yielding enantiomerically-pure N-benzoyl-L-alpha-amino acids. This synergistic coupling of two enzymes allows the ready preparation of L-alpha-amino acids of high enantiopurity in yields greater than 50%, an inherent advantage over conventional resolution procedures. Two proteases were found to catalyze the enantioselective hydrolysis of a variety of 4-substituted 2-phenylthiazolin-5-one derivatives to give N-(thiobenzoyl)-L-alpha-amino acids of high optical purity.