Ketoreductase-catalyzed dynamic reductive kinetic resolution of sterically hindered 2-aryl-1,5-benzothiazepin-3,4(2H,5H)-diones: asymmetric synthesis of a key diltiazem precursor and its analogues

An efficient, green, and stereoselective synthesis of cis -(2 S ,3 S )-2,3-dihydro-3-hydroxy-2-aryl-1,5-benzothiazepin-4(5 H )-ones was developed via ketoreductase-catalyzed dynamic reductive kinetic resolution.