3-Trifluoromethylcephalosporins. I. Total synthesis of tert-butyl (.+-.)-7-amino-3-trifluoromethyl-3-cephem-4-carboxylate.
作者:TAIICHIRO WATANABE、YOICHI KAWANO、TERUO TANAKA、TOSHIHIKO HASHIMOTO、TETSUO MIYADERA
DOI:10.1248/cpb.28.62
日期:——
tert-Butyl (±)-7-amino-3-trifluoromethyl-3-cephem-4-carboxylate (16) and the 2-cephem derivative (21) were obtained by total synthesis starting from tert-butyl N-benzylideneglycinate (1). This synthesis is the first example of the reaction of the N-benzylideneglycinate anion with a reactive α-haloketone to give a β-hydroxy-γ-halo-α-aminoester (5a and 5b). The amino esters were treated with ethyl thioformate and then potassium carbonate, leading to the 4, 5-dihydro-6H-1, 3-thiazine derivatives (8a and 8b). After cycloaddition of 8a and 8b with azidoacetyl chloride and catalytic hydrogenation of the azido group, the resulting trans 7-aminocephem compound (12) was converted to the cis isomer (16) by the established method, involving reduction of the o-nitrobenzenesul-fenimino derivative (14).
从叔丁基N-苯亚甲基甘氨酸酯(1)出发,通过全合成获得了叔丁基(±)-7-氨基-3-三氟甲基-3-头孢-4-羧酸酯(16)和2-头孢衍生物(21)。这一合成是N-苯亚甲基甘氨酸酯阴离子与活性α-卤代酮反应生成β-羟基-γ-卤代-α-氨基酯(5a和5b)的首例。氨基酯经乙基硫代甲酸酯和碳酸钾处理,生成4,5-二氢-6H-1,3-噻嗪衍生物(8a和8b)。8a和8b与叠氮乙酰氯发生环加成反应,再用催化氢化还原叠氮基,得到的反式7-氨基头孢化合物(12)通过已建立的方法转化为顺式异构体(16),涉及邻硝基苯磺亚氨基衍生物(14)的还原。