Patent ID: 7605256

Claim:
A process for preparing acid cefoxitin of formula (I) wherein: (A) a compound of formula (II) or a trimethylsilyl derivative thereof is dissolved in methylene chloride and then reacted at a temperature between −80°and −95° C. with at least one positive chlorine donor selected from the group consisting of ethyl dichlorourethane and N-chloro-succinimide, and with sodium methylate dissolved in methanol, to give a compound of formula (IV) (B) the compound of formula (IV) is desacetylated with an aqueous sodium hydroxide solution to give a compound of formula (V) and finally (C) the compound of formula (V) is carbamoylated by reaction with chlorosulphonylisocyanate in tetrahydrofuran at a temperature between −45° and −50° C., to give the aforesaid acid cefoxitin of formula (I), which is isolated in acid form; and wherein said process of preparing acid cefoxitin of formula (I) is carried out without any separation of intermediates.