Preparation of chiral synthon for HIV protease inhibitor: stereoselective microbial reduction of N-protected α-aminochloroketone

The chiral intermediate (1S,2R) [3-chloro-2-hydroxy-1-(phenylmethyl)propyl] carbamic acid, 1,1-dimethylethyl ester 2a was prepared for the total synthesis of an HIV protease inhibitor, BMS-186318. The stereoselective reduction of (1S) [3-chloro-2-oxo-1-(phenylmethyl)propyl] carbamic acid, 1,1-dimethyl-ethyl ester 1 was carried out using microbial cultures among which Streptomyces nodosus SC 13149 efficiently reduced 1 to 2a . A reaction yield of 80% was obtained. The optical purity of 99.8% and the diastereomeric purity of 99% were obtained for chiral alcohol 2a .