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LAURENT, M.; BELMANS, M.; KEMPS, L.; CERESIAT, M.; MARCHAND-BRYNAERT*, J.; Synthesis 2003, 4, 570-576; Unite Chim. Org. Med., Univ. Cathol. Louvain, B-1348 Louvain-la-Neuve, Belg.; Eng.) -C. Herrmann 30-132

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A mild and efficient procedure for the selective cleavage of N-benzhydryl protecting group of β-lactams is described. The protected 2-azetidinones 4, precursors of carbapenems, were treated with a stoichiometric amount of N-bromosuccinimide and a catalytic amount of bromine under sun light irradiation in CH 2 Cl 2-H 2 O mixture at 20°C for 3 hours. The N-benzhydrol intermediates 6, which could be isolated, were then hydrolyzed with p-TsOH in aqueous acetone to furnish β-lactams 7 and benzophenone quantitatively.