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