Penicillin sulfoxide derived azetidinone sulfinyl chlorides and related sulfinic acid derivatives are cyclized to 3-methylenecephams by reaction with Friedel-Crafts catalysts or metathetic cation forming agents.
                            青霉素亚砜衍生的氮杂环
丙烯磺酰氯和相关的
磺酸衍
生物通过与弗里德尔-克拉夫茨催化剂或交换阳离子形成剂反应,环化成3-亚甲基
头孢菌素。