A suspension of anhydrous toluene-p-sulphonic acid (0.74 g.) and 3-acetoxymethyl-7-aminoceph-3-em-4-carboxylic acid (1.17 g.) in dry DMF (17.5 ml.) was stirred for 15 minutes at room temperature to effect partial solution. One portion of 2-fluoroimidazole (0.74 g.) was then added and the mixture stirred at 90° for 2 hours. The solvent was evaporated at ambient temperature, 2% v/v aqueous HOAc (20 ml.) was added to the residue and the mixture was extracted with EtOAc (20 ml.). The aqueous layer was concentrated to 15 ml., filtered and the filtrate purified by preparative HPLC on Whatman "Partisil 10" using water/MeOH/HOAc 80:20:1 v/v/v as solvent. The product was further purified by trituration with acetone and washing with acetone and ether to give 3-acetoxymethyl-7-(imidazol-2-yl)aminoceph-3-em-4-carboxylic acid (0.42 g.) as a hydrated mixed acetate/toluene-p-sulphonate salt having m.p. >160° (decomp.) and the following n.m.r. in D2O: 2.28 (s, 3H); 3.58 (d, 1H); 3.89 (d, 1H); 4.92 (d, 1H); 5.13 (d, 1H); 5.42 (d, 1H); 5.70 (d, 1H); 7.08 (s, 2H).
