3 Tetrazolylpyridopyrimidin {HEAD ~ 4 one derivatives} useful as an antiallergy agent are produced by reacting {TAIL ~ a cyano derivative} of pyridopyrimidin 4 one compound with hydrazoic acid, followed by hydrolysis, or with a salt of hydrazoic acid, reacting the resulting product with an acid or a base, followed by hydrolysis 
are produced by reacting
3 Tetrazolylpyridopyrimidin { HEAD ~ 4 one derivatives } useful as an antiallergy agent are produced by reacting { TAIL ~ a cyano derivative } of pyridopyrimidin 4 one compound with hydrazoic acid , followed by hydrolysis , or with a salt of hydrazoic acid , reacting the resulting product with an acid or a base , followed by hydrolysis
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH