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 (1S,3R)‐N,3‐dimethylcyclohexylamine and (R)‐N‐methyl‐2‐aminohexane with excellent stereochemical purities (98 % de, 96 % ee) in good yields.