Reaction of 2-phenoxymethylpyridine (I) with diethyl ethoxymethylenemalonate (II) and n-butyllithium in THF gives ethyl 3-ethoxy-2-(ethoxycarbonyl)-4-phenoxy-4-(2-pyridyl)butyrate (III), which is cyclized to ethyl 4-oxo-1-phenoxy-4H-quinolizine-3-carboxylate (IV) by heating at 250 C in a mixture of diphenyl and diphenyl ether. Ester hydrolysis of (IV) with sodium hydroxide in methanol yields 4-oxo-1-phenoxy-4H-quinolizine-3-carboxylic acid (V), which is converted to 4-oxo-1-phenoxy-N-(1H-tetrazol-5-yl)-4H-quinolizine-3-carboxamide (VII) on treatment with carbonyldiimidazole and 5-amino-1H-tetrazole (VI) in DMF. Finally, the sodium salt of (VII) is formed by means of sodium hydroxide.