Electroenzymatic strategies for deracemization, stereoinversion and asymmetric synthesis of amino acids

A combination of a selective enzymatic oxidation with an unselective electrochemical reduction step was applied for deracemization, stereoinversion and asymmetric synthesis of l-leucine (starting from racemic leucine, d-leucine or 4-methyl-2-oxovaleric acid) in a batch reactor. d-Amino acid oxidase (d-AAO) from Trigonopsis variabilis was used as enzyme. Reaction conditions for the electrochemical and enzymatic reactions were investigated separately and finally combined to an electroenzymatic synthesis, yielding 3.5 mmol L−1 d−1 of l-leucine (ee 91%).