Pemirolast potassium (CAS NO.: 100299-08-9), with other name of 4H-Pyrido(1,2-a)pyrimidin-4-one, 9-methyl-3-(1H-tetrazol-5-yl)-, potassium salt, could be produced through many synthetic methods.

Following are some of the synthesis routes:

1) Firstly, 2-Amino-3-methylpyridine (I) is condensed with ethoxymethylenemalonodinitrile (II) to afford the monocyclic intermediate (III), which is in tautomeric equilibrium with the pyridopyrimidine derivative (IV). Next, the reaction of (IV) with aluminum azide (AlCl₃.NaN₃) in refluxing THF yields 4-imino-9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidine (V). Finally, this compound is first hydrolyzed with 1N HCl and then treated with KOH.
2) Compound (IV) can be converted to the final product by a one-pot reaction: (VI) is treated first with NaN₃ in refluxing acetic acid, then hydrolyzed with HCl and finally treated with KOH.