A Novel (<i>R</i>)‐Imine Reductase from <i>Paenibacillus lactis</i> for Asymmetric Reduction of 3 <i>H</i>‐Indoles

Abstract

Abstract A novel ( R )‐imine reductase ( Pl RIR) from Paenibacillus lactis was heterologously overexpressed in Escherichia coli , purified and characterized. The purified Pl RIR exhibited relatively high catalytic efficiency ( k cat / K m =1.58 s −1 m m −1 ) towards 2,3,3‐trimethylindolenine. A panel of 3 H ‐indoles and 3 H ‐indole iodides were reduced by Pl RIR to yield the corresponding products with good‐to‐excellent enantioselectivity (66–98 % ee ). In addition, Pl RIR also possesses good activities toward other types of imines such as pyrroline, tetrahydropyridine, and dihydroisoquinoline, indicating a reasonably broad substrate acceptance. In a 100 mg scale preparative reaction, 100 m m 2,3,3‐trimethylindolenine was converted efficiently to afford ( R )‐2,3,3‐trimethylindoline with 96 % ee and 81 % yield.