Biocatalytic process for preparing eslicarbazepine and analogs thereof

A process for preparing a compound of structural formula (1) in enantiomeric excess,

• wherein
• each ring A and B is independently an optionally substituted monocyclic aryl or heteroaryl,
• R1 is selected from hydrogen, hydroxy, halo, cyano, carboxy, and an optionally substituted alkyl, aminoalkyl, cycloalkyl, heterocycloalkyl, alkyloxycarbonyl, aminocarbonyl, aminothiocarbonyl, aminosulfonyl, and sulfonyl;
• the process comprising contacting the compound of structural formula (2),
• wherein A and B, and R1 are defined above, with a ketoreductase polypeptide comprising an amino acid sequence that has at least 80% sequence identity to the reference polypeptide of SEQ ID NO:
• 10, wherein the amino acid sequence comprises X80 is T;
• X96 is V or R;
• X145 is L;
• X153 is T;
• X190 is P;
• X196 is L or M;
• and X226 is V, wherein the ketoreductase is capable of converting compound (2) to compound (1) in enantiomeric excess, in presence of NADH or NADPH under suitable reaction conditions.