Structure-guided mining of stereoselective reductive aminases for biocatalytic stereodivergent synthesis of chiral piperidinamine and derivatives.

Chiral azacyclic amine derivatives occupy a vital role of nitrogen-containing compounds, due to serve as foundational motifs in numerous pharmaceuticals and bioactive substances. Novel complementary enantioselective reductive aminases IRED9 and IRED11 were unveiled through comprehensive gene mining from Streptomyces viridochromogenes and Micromonospora echinaurantiaca, respectively, which both demonstrated enantiomeric excess (ee) values and conversion ratios of up to 99 % towards N-Boc-3-pyridinone (NBPO) and cyclopropylamine. IRED9 exhibited the highest activity at pH 8.0 and 45 °C，while IRED11 have optimal conditions at pH 8.0 and 50 °C. A variety of amine donors and ketones could be converted by IRED9 and IRED11 for asymmetric synthesis of piperidinamine and derivatives with complementary enantioselectivity. Through preparative-scale synthesis of (S)- and (R)-3-piperidinamine, IRED9 and IRED11 demonstrate substrate loadings of 120 g·L-1 and 40 g·L-1 with 98 % yield and 99 % ee, respectively. The space time yield (STY) reached 142.7 g·L-1d-1 and 47.1 g·L-1d-1 for the S enantiomer and R enantiomer, respectively. Interaction analysis indicated the substrate orientation and strong charge attraction interaction are vital factors for enantioselectivity of IREDs. This study unveils novel enantioselective reductive aminases for stereodivergent synthesis of piperidinamine and derivatives at high substrate loading.