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