| abstract |
A process for preparing compounds of the formula I: <CHEM> wherein X is sulphur, oxygen, methylene or sulphinyl (R or S configuration), R<3> is hydrogen or methoxy, R<4> 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) <CHEM> with a compound of formula (III) <CHEM> wherein R<4> 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. |