Asymmetric Reductive Amination of Ketones Catalyzed by Imine Reductases

Biocatalysis employing imine reductases is a promising approach for the one‐step generation of chiral amines from ketones. The enzymes reported for this process suffer from low activity and moderate stereoselectivity. We identified a set of enzymes that facilitate this reaction with high to quantitative conversions from a library of 28 imine reductases. This enabled the conversion of ketones with ammonia, methylamine, or butylamine into the corresponding amines. Most importantly, we performed preparative (>100 mg) scale syntheses of amines such as (1 S ,3 R )‐ N ,3‐dimethylcyclohexylamine and ( R )‐ N ‐methyl‐2‐aminohexane with excellent stereochemical purities (98 %  de , 96 %  ee ) in good yields.