A novel process for preparing cephalosporins, and intermediates which can be used in the process

摘要

A process for the preparation of compounds of formula I wherein R1 represents hydrogen or a hydroxy-proctecting group, R2 represents hydrogen, a cation, the pivaloyloxymethyl group or a carboxy-protecting group and R3 represents hydrogen, the acetoxy group, the carbamoyloxy group, a group S-Y whereby Y represents an unsubstituted or substituted heterocycle, or an optionally substituted pyridinium of formula whereby R4 and R5 are the same or different and each represent hydrogen, halogen, alkyl, hydroxy, carboxamido, alkoxycarbonyl amino, monoalkylamino or di-alkylamino or together represent an optionally substituted 5- or 6-membered carbocyclic ring, characterised by reacting a compound of formula IV wherein R1 represents a hydroxy protecting group and represents a 5- or 6-membered heterocycle which may contain in addition to the nitrogen atom one or two further heteroatoms and which may be substituted or anellated with an optionally sustituted benzene ring with a compound of formula III and if desired deprotecting the obtained end product and optionally converting an obtained product into a salt or vice-versa.