(1'R, 3R, 4R)-N-substituted -3-(1'-hydroxyethyl)-4-acetoxy-β- lactams(3), a key intermediate for synthesis of the bapenem and carbapenem, has been efficiently synthesized using inexpensive L - ascorbic acid (4) as the chiral reagent. (S) - glyceraldehyde acetonide (5) was prepared conveniently by three steps from 4, and condensed with amines to give the chiral imines (6). The [2+2]-cycloaddition of diketene with the chiral imines(6) underwent in a highly stereoselective manner to give a series of 3(S)-acetyl-β-lactams(8). The target compound 3a was then obtained through further reactions from 8a.

Key words: ACETOXY GROUP, STEREOSELECTIVITY, CYCLOADDITION REACTION, ASCORBIC ACID, BETA LACTAM, ANTIBIOTICS