Jz. Crich et al., ENZYMATIC ASYMMETRIC-SYNTHESIS OF ALPHA-AMINO-ACIDS - ENANTIOSELECTIVE CLEAVAGE OF 4-SUBSTITUTED OXAZOLIN-5-ONES AND THIAZOLIN-5-ONES, Journal of organic chemistry, 58(12), 1993, pp. 3252-3258
A general enzymatic asymmetric synthesis of L-alpha-amino acids has be
en developed. This method entails the use of the Pseudomonas cepacia l
ipase (P-30) to catalyze the enantioselective methanolysis of a variet
y of 4-substituted 2-phenyloxazolin-5-one derivatives in a nonpolar or
ganic 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 resol
ution procedures. Two proteases were found to catalyze the enantiosele
ctive hydrolysis of a variety of 4-substituted 2-phenylthiazolin-5-one
derivatives to give N-(thiobenzoyl)-L-alpha-amino acids of high optic
al purity.