Synthesis and antiallergic activity of some acidic derivatives of 4H-pyrimido[2,1-b]benzazol-4-ones

Reactions of 2-aminobenzothiazole, 2-aminobenzoxazole, and 2-amino-1-methylbenzimidazole with dimethyl aminofumarate (DMAF) or diethyl ethoxymethylenemalonate (DEEM) led to 2- or 3-carboxy-4H-pyrimido[2,1-b]-benzazol-4-ones, respectively. Subsequent derivatization of these carboxylic acids gave the corresponding tetrazolylcarboxamides and tetrazoles. These acidic compounds were tested in the rat passive cutaneous anaphylaxis (PCA) assay as potential antiallergic agents. Many of the compounds displayed activity comparable to that shown by disodium cromoglycate (DSCG) when tested by the intraperitoneal route, and some, unlike DSCG, also showed activity when tested orally.