Enantioselective Cascade Biocatalysis for Deracemization of Racemic β‐Amino Alcohols to Enantiopure (S)‐β‐Amino Alcohols by Employing Cyclohexylamine Oxidase and ω‐Transaminase

Optically active β‐amino alcohols are very useful chiral intermediates frequently used in the preparation of pharmaceutically active substances. Here, a novel cyclohexylamine oxidase (ArCHAO) was identified from the genome sequence of Arthrobacter sp. TYUT010‐15 with the R‐stereoselective deamination activity of β‐amino alcohol. ArCHAO was cloned and successfully expressed in E. coli BL21, purified and characterized. Substrate‐specific analysis revealed that ArCHAO has high activity (4.15 to 6.34 U mg−1 protein) and excellent enantioselectivity toward the tested β‐amino alcohols. By using purified ArCHAO, a wide range of racemic β‐amino alcohols were resolved, (S)‐β‐amino alcohols were obtained in >99 % ee. Deracemization of racemic β‐amino alcohols was conducted by ArCHAO‐catalyzed enantioselective deamination and transaminase‐catalyzed enantioselective amination to afford (S)‐β‐amino alcohols in excellent conversion (78–94 %) and enantiomeric excess (>99 %). Preparative‐scale deracemization was carried out with 50 mM (6.859 g L−1) racemic 2‐amino‐2‐phenylethanol, (S)‐2‐amino‐2‐phenylethanol was obtained in 75 % isolated yield and >99 % ee.