Reaction Steps
A solution of 4-methoxybenzyl (6R,7R)-3-[(2RS,5SR)-5-methoxymethyltetrahydrofuran-2-yl]-7-phenoxyacetamidoceph-3-em-4-carboxylate (1.93 g) in dichloromethane (25 ml) was cooled to -15 to -20° C., N-methylmorpholine (0.75 ml) was added followed by a solution of phosphorus pentachloride in dichloromethane (26.5 ml of a solution containing 40 mg·ml-1). The mixture was stirred at the same temperature for 0-5 h and then methanol (6.8 ml) was added and the mixture stirred at room temperature for 0.5 h. Water (10 ml) was then added and the mixture vigorously stirred for 0.5 h. The dichloromethane was then removed on a rotary evaporator and the residue was partitioned between ether and water. The aqueous phase was stirred with ethyl acetate and the pH was adjusted to 6.2 with 1N aqueous ammonia. The organic phase was washed with water and brine, dried over magnesium sulphate and evaporated. The products were separated by column chromatography of the residue using gradient elution (silica gel, 1:1 hexane:ethyl acetate going to neat ethyl acetate). The following were obtained in order of elution 4-methoxybenzyl (6R,7R)-7-amino-3-[(2S,5R)-5-methoxy-methyltetrahydrofuran-2-yl]ceph-3-em-4-carboxylate (388 mg); νmax (CHCl3) 3410, 1776 and 1725 cm-1 ; δH (CDCl3) 1.59-1.78 (2H,m), 1.93-2.08 (1H,m), 2.18-2.32 (1H,m), 2.54 (2H, br s), 3.33-3.54 (3H,m), 3.38 (3H,s), 3.80 (3H,s), 4.00-4.11 (1H,m), 4.76 (1H,d, J 4.99 Hz), 4.90 (1H,d, J 4.97 Hz) 4.96 (1H,t, J 8.23 Hz) 5.17 (2H,s), 6.88 (2H,d, J 8.60 Hz) and 7.33 (2H,d, J 8.61 Hz). [Mass spectrum: M+ (434)]; 4-methoxybenzyl (6R,7R)-7-amino-3-[(2R,5S)-5-methoxymethyltetrahydrofuran-2-yl]ceph-3-em-4-carboxylate (305 mg); νmax (CHCl3) 3409, 1776 and 1725 cm-1 ; δH (CDCl3) 1.60-1.81 (2H, m), 1.85-2.01 (2H, m), 3.30-3.50 (2H, m), 3.38 (3H, s), 3.44 (1H,d, J 17.78 Hz), 3.69 (1H, d, J 17.75 Hz), 3.80 (3H, s), 4.00-4.17 (1H,m), 4.70 (1H, d, J 4.92 Hz), 4.93 (1H, d, J 4.95 Hz), 5.10-5.20 (1H, m), 5.18 (1H, d, J 11.88 Hz), 5.24 (1H, d, J 11.89 Hz), 6.88 (1H,d, J 8.65 Hz) and 7.35 (1H, d, J 8.64 Hz). [Mass spectrum: M+ (434)].
