Radical Cyclization Approach to 4-Oxo-2-azetidineacetic Acids: Synthesis of a Chiral Key Intermediate for Carbapenem Antibiotic PS-5

Hiroyuki Ishibashi; Kazuya Kodama; Chisato Kameoka; Hirotaka Kawanami; Masazumi Ikeda

doi:10.1055/s-1995-5143

Synlett 1995; 1995(9): 912-914
DOI: 10.1055/s-1995-5143

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Radical Cyclization Approach to 4-Oxo-2-azetidineacetic Acids: Synthesis of a Chiral Key Intermediate for Carbapenem Antibiotic PS-5

Hiroyuki Ishibashi^* , Kazuya Kodama, Chisato Kameoka, Hirotaka Kawanami, Masazumi Ikeda¹

^*Kyoto Pharmaceutical University, Misasagi, Yamashina, Kyoto 607, Japan

Abstract

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α-Bromo amide 8 bearing phenyl and phenylthio substituents at the terminus of the N-vinylic bond underwent radical cyclization in a 4-exo-trig manner to give β-lactam 9, which was transformed, via oxidation of its phenyl group, into the key intermediate 14 for the synthesis of (±)-PS-5. The chiral key intermediate 23 for (+)-PS-5 was also obtained via an asymmetric radical cyclization of bromide 16 bearing (S)-1-phenylethyl group on the nitrogen atom.

4-oxo-2-azetidineacetic acid - (S)-(-)-1-phenylethylamine - (+)-PS-5 - radical cyclization - ruthenium tetroxide oxidation

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