The kinetic resolution of amino acid esters (AAEs) is a useful synthetic strategy for the preparation of single‐enantiomer amino acids. The development of an enzymatic dynamic kinetic resolution (DKR) process… Click to show full abstract
The kinetic resolution of amino acid esters (AAEs) is a useful synthetic strategy for the preparation of single‐enantiomer amino acids. The development of an enzymatic dynamic kinetic resolution (DKR) process for AAEs, which would give a theoretical yield of 100 % of the enantiopure product, would require an amino acid ester racemase (AAER); however, no such enzyme has been described. We have identified low AAER activity of 15 U mg−1 in a homologue of a PLP‐dependent α‐amino ϵ‐caprolactam racemase (ACLR) from Ochrobactrum anthropi. We have determined the structure of this enzyme, OaACLR, to a resolution of 1.87 Å and, by using structure‐guided saturation mutagenesis, in combination with a colorimetric screen for AAER activity, we have identified a mutant, L293C, in which the promiscuous AAER activity of this enzyme towards l‐phenylalanine methyl ester is improved 3.7‐fold.
               
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