Nitrogen bridgehead compounds. 33. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 2.

A series of 9-hydrazono-4H-pyrido[1,2-a]pyrimidin-4-ones was prepared. The compounds were evaluated in the rat passive cutaneous anaphylaxis test for antiallergic activity. Structure-activity relationship studies revealed that the presence of a monosubstituted hydrazone moiety in position 9 and an unsubstituted 2-position are necessary for the intravenous activity.