Biocatalysts for ezetimibe synthesis

A method for preparing compound of Formula (Ia) in diastereomeric excess

• wherein,
• X is C or S;
• R1 is selected from —H, —F, —Cl, —Br, or —I;
• R2 is selected from —H, —F, —Cl, —Br, —I, —CN, —OH (optionally protected with a hydroxyl protecting group), —CH2NH2 (optionally protected with a nitrogen protecting group), and any one of the following optionally substituted groups:
• alkyl, alkoxy, alkenyl, alkenoxy, alkynyl, alkynoxy, cycloalkyl, aryl, heteroaryl, or heterocycle;
• R3 is selected from —H, —F, —Cl, —Br, —I, —CN, —OH (optionally protected with a hydroxyl protecting group), —CH2NH2 (optionally protected with a nitrogen protecting group), and any one of the following optionally substituted groups:
• alkyl, alkoxy, alkenyl, alkenoxy, alkynyl, alkynoxy, cycloalkyl, aryl, heteroaryl, or heterocycle;
• R4 is selected from —H, —F, —Cl, —Br, —I, —CN, —OH (optionally protected with a hydroxyl protecting group);
• and
• R5 is selected from —H, —F, —Cl, —Br, —I, —CN, —OH (optionally protected with a hydroxyl protecting group), —CH2NH2 (optionally protected with a nitrogen protecting group), and any one of the following optionally substituted groups:
• alkyl, alkoxy, alkenyl, alkenoxy, alkynyl, alkynoxy, cycloalkyl, aryl, heteroaryl, or heterocycle;
• said method comprising:
• contacting a compound of Formula (IIa), wherein, X, R1, R2, R3, R4, and R5 are as defined above,
• with a non-naturally occurring ketoreductase polypeptide in the presence of cofactor NADPH or NADH under suitable reaction conditions, wherein the polypeptide comprises an amino acid sequence having at least 80% sequence identity to SEQ ID NO:2 and the following amino acid residues:
• R at position X40;
• I or L at position X153;
• A, or P at position X190;
• A, C, N, S, or T at position X196;
• F or W at position X199;
• and I at position X206.