Preparing β-blocker (R)-Nifenalol based on enantioconvergent synthesis of (R)-p-nitrophenylglycols in continuous packed bed reactor with epoxide hydrolase

Abstract An engineered epoxide hydrolase from Vigna radiate ( Vr EH2 M263N ) shows near-perfect enantioconvergence in single enzyme mediated hydrolysis of racemic p -nitrostyrene oxide (pNSO). To explore industrial potential of the promising biocatalyst, we tried to immobilize the Vr EH2 variant by covalently linking onto a commercially available amino resin ECR8405F. Then a 5-mL packed bed reactor filled with the immobilized Vr EH2 M263N was connected with macroporous resin NKA-11 for in situ product adsorption, and the product ( R ) -p- nitrophenyl glycol (pNPG) was harvested by methanol elution, with 91% isolated yield and 97% ee . The continuous reactor was operated stably for more than 100 h with a space time yield of 20 g L −1  h −1 . Subsequently, the β -blocker ( R )-Nifenalol was prepared by chemically synthesized from ( R )-pNPG, affording the product in an overall yield of 61.3% (1.5 g) and an enantiopurity of 99.9% ee after recrystallization.