Salts in the preparation of cephalosporin antibiotics

A process for the preparation of compound of formula (II),

• wherein R1 represents
• wherein R4 represents hydrogen or —CHO group and R5 represents hydrogen or trityl,
• R2 represents hydrogen or methoxy group,
• R3 represents —CH═CH2 or
• and
• M represents a dialkyl or dicycloalkyl ethylenediamine group selected from N,N′-diisobutylethylenediamine, N,N′-dicyclohexylethylenediamine, and N,N′-dicyclopentylethylenediamine,
• the process comprising:
• i) condensing a compound of formula (VI)
• with a compound of formula (VII) wherein Y is selected from halogens, or a group which forms together with the —C═O group to which Y is attached an active ester, and a group which forms together with the —C═O group to which Y is attached a mixed anhydride in the presence of a base and solvent to produce a compound of formula (VIII);
• and
• ii) treating the compound of formula (VIII) with a compound M selected from N,N′-diisobutylethylenediamine, N,N′-dicyclohexylethylenediamine, and N,N′-dicyclopentylethylenediamine to produce the compound of formula (II).