Process for preparing cephalosporin derivatives

摘要

A process for the manufacture of a cephalosporin derivative of the formula I <IMAGE> I in which X is sulphur, oxygen or sulphinyl; R1 is any one of the C-3 substituents from antibacterially-active cephalosporins known in the art; R2 is hydrogen or 1-6C alkyl; R3 is hydrogen or 1-6C alkyl; and the pharmaceutically-acceptable acid-addition and base-addition salts thereof, characterized by cyclization of a compound of the formula II: <IMAGE> II or a derivative thereof in which the carbonyl group is masked, or an acid-addition salt thereof, in which R4 and R5 individually have one of the values for R2 and R3, R6 is a nitrogen-protecting group and R7 is hydrogen or any one of the cephalosporin 3-carboxylic acid protecting groups known in the art; whereafter when the product from the cyclization retains the protecting group R7 (when R7 is other than hydrogen) the protecting group R7 is replaced by hydrogen by conventional means; and whereafter when the compound of the formula I is obtained in the form of the free base or salt, and a pharmaceutically-acceptable salt or free base respectively is required, any necessary conversion between free base and salt is carried out by conventional means.