Amino cephem compound (II) was condensed with acid (I) using phosphoryl chloride and pyridine to yield amide (III). After conversion of the chloromethyl group of (III) into the correspondig iodide (IV) upon treatment with NaI in acetone, displacement of the halogen atom with 2-mercaptothiazolo[4,5-c]pyridine (V) in DMF provided sulfide (VI). Quaternization of the pyridine nitrogen atom of (VI) with CH3I, to give pyridinium salt (VII).

Pyridinium salt (VII) was followed by deprotection of the N-trityl and the benzyl ester groups in trifluoroacetic acid containing anisole, to furnish acid (VIII) as the inner salt with the pyridinium group. The remaining carboxylic acid group of (VIII) was finally converted to the sodium salt upon treatment with aqueous NaHCO3, and the target compound was purified by Diaion HP-20 column chromatography.