The team of Shushan Gao at the Institute of Microbiology, Chinese Academy of Sciences reported the tuning of imine reductase for the asymmetric synthesis of azetidinium through concise structure-directed engineering. The related research results were published in the leading international academic journal German Applied Chemistry on March 23, 2022.
Although imine reductases (IREDs) are attractive reductive amidases (RedAms), their substrate range is still narrow and rational engineering is rare. In this paper, focusing on hydrogen bond reorganization and cavity expansion, researchers devised a concise strategy combining rational cavity design, combined active center saturation test (CAST), and thermal stability engineering to convert weakly active IR-G36 into a variant M5 with excellent performance for the synthesis of (R)-3-benzyl amino-1-Boc-piperidine with a 4193-fold increase in catalytic efficiency and Tm 16.2 °C and a significant increase in e.e. values from 78% (R) to >99% (R). M5 demonstrates a wide range of substrates for the synthesis of multiple azetidiniums and demonstrates the reaction on a hundred-gram scale under industrially relevant conditions.
This study provides a compelling example of the preparation of versatile and efficient IREDs, with exciting opportunities in medicinal and process chemistry as well as synthetic biology.
The structural analysis aspect of this study was performed by Suzhou ReadCrystal Technology Co.