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 CH2Cl2-H2O 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.
本文描述了一种选择性裂解δ-内酰胺的 N-二苯甲基保护基的温和而高效的方法。受保护的
2-氮杂环丁酮 4 是碳青霉烯类化合物的前体,在 20 °C 的
CH2Cl2-
H2O 混合物中,用等量的 N-
溴代丁二
酰亚胺和催化量的
溴在太阳光照射下处理 3 小时。然后在
丙酮水溶液中用 p-TsOH 进行
水解,定量生成 δ-内酰胺 7 和
二苯甲酮。