Synthesis of 7‐[α‐(2‐aminothiazol‐4‐yl)‐α‐(z)‐methoximinoacetamido]‐3‐(1‐[ 14 C]methylpyrrolidinio)‐methyl‐3‐cephem‐4‐carboxylate sulfate

The synthesis of the title compound (6) is described. The reaction of sodium [ 14 C] formate with acetyl chloride produced the mixed anhydride. Treatment with pyrrolidine gave the N‐formyl compound in a 4 to 1 ratio with the N‐acetyl compound. 1 Separation and reduction with lithium aluminum hydride gave N‐[ 14 C]methylpyrrolidine 2 . Reaction with 7‐[α‐(2‐triphenylmethylaminothiazol‐4‐yl)‐α‐(z)‐methoximinoacetamido]‐1‐oxo‐3‐iodomethyl‐3‐cephem‐4‐carboxylate diphenylmethyl ester introduced the label into the cephalosporin. Treatment with acetyl chloride converted the sulfoxide to the sulfide. Formic acid at 39°C removed the protecting groups and treatment with 4N sulfuric acid produced the title compound as a sulfate salt.