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Sang Hyup Lee College of Pharmacy, Duksung Women’s University, Seoul 132-714, Korea. E-mail: sanghyup@duksung.ac.krReceived May 16, 2014, Accepted June 15, 2014The studies on design and synthesis of new monocyclic β-lactam esters 4(R/S)-(1'-methoxycarbonylpropyl-2'(R/S)-thio)-3(R)-phenylacetamidoazetidin-2-one (3a) and 4(R/S)-(1'-methoxycarbonyl-2'-methyl-propyl-2'-thio)-3(R)-phenylacetamidoazetidin-2-one (3b) were described. Compounds 3a and 3b were specificallydesigned to retain all penicillin substructures except the bicyclic system, which would be conceived by cleavingthe C(3)–N(4) bond of penicillin G. Compounds 3a and 3b are of particular interest in the context of thestructural elucidation of monocyclic β-lactams originated from penicillin. Key intermediates, β-mercaptoesters 6a and 6b, were synthesized from conjugate acids 4a and 4b using three-step synthetic sequences,respectively, and 4(S)-acetoxy-3(S)-phenylacetamidoazetidin-2-one (7) was obtained from the degradation ofpenicillin G. Reactions of 6a and 6b with 7, thus obtained, provided the target compounds 3a and 3b,respectively.Key Words : Monocyclic β-lactams, 3-mercaptobutanoate, Acetylthio, AzetidinoneIntroductionOf the diverse compounds that display antibacterialactivities, β-lactams are still considered valuable antibiotics.In particular, the monocyclic β-lactam series

Studies on the Design and Synthesis of New Monocyclic β-Lactams Containing Substructures of Penicillin G