Optical Resolution of Non-Protein Amino Acids by Lipase-Catalyzed Ester Hydrolysis

Abstract

The enantioselectivity of the lipase-catalyzed hydrolysis of amino acid esters was found to be strongly dependent on the source of the enzyme, the N-protecting group and the alcohol moiety of the ester group. The 2-chloroethyl esters of the N-benzyloxycarbonyl (Z) derivatives of a number of non-protein amino acids, both aliphatic and aromatic, were converted by Aspergillus niger lipase into enantiomerically enriched Z-amino acids with fairly high optical purities, the L-enantiomers being preferentially hydrolyzed. A mammalian lipase from porcine pancreas also catalyzed the highly enantioselective hydrolysis of the 2-chloroethyl or 2,2,2-trifluoroethyl esters of the N-Z derivatives of non-protein amino acids. The results obtained in this work indicate that suitable selection of amino acid derivatives and enzymes allows highly enantioselective hydrolysis with moderate to high reaction rate useful for the optical resolution of non-protein amino acids.

Key Words:

• Optical resolution
• Non-protein amino acids
• Enantioselective hydrolysis
• Microbial lipases
• Porcine pancreatic lipase
• Enantioselectivity