| abstract |
Cephalosporin derivatives of the formulae ##STR1## wherein X is sulphur, oxygen, methylene or sulphinyl, R3 is hydrogen or methoxy, R54 is hydrogen or a carboxyl protecting group, R 51 is a (1-4C)alkyl group, R 4 is hydrogen, (1-4C)alkyl, halo(1-4C)alkyl, hydroxy(1-4C)alkyl, (1-4C)alkoxy(1-4C)alkyl, carboxy (1-4C)alkyl, amino (1-4C)alkyl, cyano(1-4C)alkyl, (1-4C)alkanoylamino(1-4C)alkyl, allyl, furfuryl, benzyl or pyridyl(1-4C)alkyl and R 52 is an amino protecting group and salts thereof are useful as intermediates in the preparation of cephalosporin antibiotics. |