Synthesis and antiallergy activity of 4-oxopyrano[3,2-b]indoles

A series of 4-oxopyrano[3,2-b]indole carboxylic acids, tetrazoles, and carboxamidotetrazoles has been prepared and tested for antiallergy potential in the rat passive cutaneous anaphylaxis (PCA) assay. Many of the compounds showed activity comparable or superior to that of cromolyn sodium or doxantrazole. Several compounds were orally active.