Process för framställning av cephemderivat

摘要

A process for preparing B-lactam derivatives of the formula (I): (I) wherein R1 represents hydrogen or a metal salt; and R2 represents hydrogen, acetoxy methyl, (2,5-dihydro-2-methyl-6-hydroxy-5-oxo-as-triazin-3-yl)thiomethyl or (1-methyl-1-H-tetrazol-5-yl)thiomethyl is disclosed. This process comprises the steps of (a) reacting triphenylphosphine and hexachloroethane or carbon tetrachloride with 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid in an organic solvent to give the corresponding acyloxyphosphonium chloride derivative of the formula: (b) acylating a previously silylated derivative of 7-ACA with this acyloxyphosphonium chloride derivative without its isolation.