The present invention relates to a process for preparing key intermediates for cephalosporin antibiotics substantially free of undesired delta A2 isomer. Thus, 7-aminocephalosporanic acid (7-ACA) is silylated with hexamethyldisilazane in cyclohexane at reflux temperature. (6R,7R)-3-[(Acetyloxy)methyl]-7-(trimethylsilyl)aminoceph-3-em-4-oic acid obtained is reacted with the mixture of N-methylpyrrolidine and trimethylsilyliodide in cyclohexane, desilylated with isopropyl alcohol and treated with hydrochloric acid to obtain [6R-(6a,7b)]-1-[[7-Amino-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl]methyl]-1-methylpyrrolidinium inner salt hydrochloride. [6R-(6a,7b)]-1-[[7-Amino-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl]methyl]-1-methylpyrrolidinium inner salt hydrochloride is N-acylated with syn-2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid 2-benzothiazolyl thioester (MAEM) followed by treatment with hydrochloric acid to give cefepime dihydrochloride monohydrate.
本发明涉及一种制备
头孢菌素抗生素的关键中间体的方法,该方法基本上不含不需要的δA2异构体。因此,7-
氨基头孢菌酸(
7-ACA)在
环己烷中与
六甲基二硅氮烷在回流温度下
硅化。得到的(6R,7R)-3-[(乙酰氧)甲基]-7-(三甲基
硅基)
氨基头孢-3-烯-4-酸与
N-甲基吡咯烷和三甲基
硅碘酸酯的混合物在
环己烷中反应,用
异丙醇脱
硅,然后用
盐酸处理,得到[6R-(6a,7b)]-1-[[7-
氨基-2-羧基-8-氧代-5-
硫代-1-
氮杂双环[4.2.0]辛-2-烯-3-基]甲基]-
1-甲基吡咯烷内盐盐酸盐。[6R-(6a,7b)]-1-[[7-
氨基-2-羧基-8-氧代-5-
硫代-1-
氮杂双环[4.2.0]辛-2-烯-3-基]甲基]-
1-甲基吡咯烷内盐盐酸盐与syn-2-(
2-氨基噻唑-4-基)-2-甲氧基亚
氨基
乙酸2-
苯并噻唑基
硫酯(
MAEM)N-酰化,然后用
盐酸处理,得到
头孢哌酮二盐酸盐一
水合物。