Process for the preparation of cephalosporin derivatives

摘要

The invention relates to a novel process for preparing a useful cephalosporin of the general formula (I) in which R1 is a lower alkyl group which may optionally be substituted by a carboxyl or protected carboxyl group; R2 is a hydrogen atom or a carboxyl protective group; and R3 is a nitrogen-containing, substituted or unsubstituted heterocyclic group which is bonded to the exo-methylene group in position 3 of the cephem ring via a carbon- nitrogen bond, which cephalosporin is prepared from a compound of the general formula (II) by a dehydration reaction.