| abstract |
Cephalosporin derivatives of the formulaewherein X is sulphur, oxygen, methylene or sulphinyl, R3 is hydrogen or methoxy, R54 is hydrogen or a carboxyl protecting group, R<sup>51</sup> is a (1-4C)aklyl group, R<sup>4</sup> 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 pyridy(1-4C)alkyl and R<sup>52</sup> is an amino protecting group and salts thereof are useful as intermediates in the preparation of cephalosporin antibiotics. |