Patent ID: 7083973

Claim:
A stereoselective process for the preparation of (3S,2R)-1-halo-2-hydroxy-3-(protected)amino-4-substituted butanes represented by the formula I wherein Hal is halogen, R is selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl and R 1 is a protecting group for the amino function comprising contacting a (3S)-1-halo-2-oxo-3-(protected)amino-4-substituted butane represented by formula II wherein Halo, R and R 1 are as defined above with a microorganism capable of catalyzing the stereoselective reduction of the compound represented by formula II wherein said microorganism is selected from the group consisting of Rhodococcus erythropolis ATCC 4277 , Rhodococcus etythropolis DSM 6971 , Rhodococcus sp. ATCC 21227 , Rhodococcus erythropolis ATCC 27854 and Brevibacterium sp. ATCC19653 under conditions such that said reduction is effected, and recovering said compound represented by formula I.