Penicillin sulfoxides are converted to 3-halo-3-methyl-cepham-4-carboxylic acid esters and amides or the corresponding cephem derivatives by heating the penicillin sulfoxide precursor in a polyhaloalkane solvent to a temperature between 50.degree. to about 150.degree. C. in the presence of an equimolar amount of a neutral or basic catalyst, respectively. The catalysts employed are bases such as pyridine, picoline, lutidine, quinoline, isoquinoline, dimethylaniline or a quaternary ammonium salt. The 3-halo-cepham intermediates produced with a quaternary ammonium catalyst are dehydrohalogenated to afford known cephem derivatives or converted to the free 4-carboxylic acid and the alkali metal, alkaline earth metal or ammonium salts thereof to afford novel antibacterial agents.
                            青霉素亚
磺酸酯经在多卤代烷溶剂中,在50度至约150度C的温度下,在中性或碱性催化剂的存在下,分别转化为3-卤代-3-甲基-头孢四烯-4-
羧酸酯和酰胺或相应的
头孢菌素衍
生物。所使用的催化剂是碱性物质,如
吡啶、
哌啶、戊啶、
喹啉、
异喹啉、二甲基
苯胺或季
铵盐。用季
铵盐催化剂产生的3-卤代-头孢烯中间体经脱卤化反应,得到已知的
头孢菌素衍
生物或转化为自由的4-
羧酸和碱
金属、碱土
金属或
铵盐,从而得到新的抗菌剂。