(R)-N-Benzyl-4-[(methoxycarbonyl)methyl]-2-azetidinone (10) and (S)-4-[(methylcarbonyl)methyl]-2-azetidinone (17) were enantioselectively synthesized from the benzylamino ester 3, which was prepared by the highly stereoselective 1,4-addition of benzylamine to the α,β-unsaturated ester 2 derived from D-glyceraldehyde acetonide (1).