PROCESS FOR PREPARING CEPHALOSPORIN COMPOUNDS

A process for preparing compounds of the formula I: (I) wherein X is sulphur, oxygen, methylene or sulphinyl (R or S configuration), R3 is hydrogen or methoxy, R4 is an optionally substituted (1-4C)alkyl group, Y is hydrogen or a carboxyl protecting group and Q is an optionally protected amino group or an acylamino group, which comprises reacting a compound of formula (II) (II) with a compound of formula (III) (III) wherein R4 is as defined above and W and Z represent hydrogen atoms or a group or groups removable to yield the compound of formula (I). The compounds of the formula I are useful intermediates in the preparation of cephalosporin antibiotics.