Stereoselective Biosynthesis of Bichiral Amino Alcohols from Diketone via Difunctionalization

Chiral amino alcohols are vital in many biologically active molecules and natural products and are crucial building blocks for the pharmaceutical industry. However, the chemosynthesis of chiral amino alcohols, particularly bichiral amino alcohols, faces challenges related to chemoselectivity and enantioselectivity. Here, a dual-enzyme cascade pathway for the synthesis of bichiral amino alcohols through difunctionalization, exhibiting both high chemo- and stereoselectivity, was proposed for the first time. Among them, NADPH-dependent <i>meso</i>-diaminopyrimidate dehydrogenase from Proteus vulgaris (<i>Pv</i>DAPDH) exhibited (<i>R</i>)-selective reductive amination activity, converting ketones into chiral amines; natural glucose dehydrogenase from Bacillus megaterium (<i>Bm</i>GDH) not only facilitated NADPH regeneration but also catalyzed the reductive hydroxylation of ketones to chiral alcohols. Second, the rational design of the rate-limiting enzyme <i>Pv</i>DAPDH generated the mutant M4 with increased specific activity and catalytic efficiency (<i>k</i> _cat/<i>K</i> _m) for <b>16a</b> up to 3.2- and 10.3-fold, respectively, compared to the wild type. Additionally, the yield of mutant M4 for <b>1a</b>-<b>16a</b> increased by 1.1- to 37-fold compared to the wild type. Finally, two high-value bichiral amino alcohols (<b>14b</b> and <b>16b</b>) were asymmetrically synthesized from the corresponding bietone via a one-pot dual-enzyme cascade, exhibiting excellent stereoselectivity (dr ≥ 98:2). These findings provide a potential biosynthetic pathway for the green synthesis of bichiral amino alcohols and complement existing synthetic methods.