Synthesis and antiinflammatory and analgesic activity of 5-aroyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acids and related compounds

5-Acyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acids and the homologous pyridine and azepine derivatives were synthesized and assayed for antiinflammatory and analgesic activity. 5-Benzoyl-1,2-dihydro-3H-pyrrolo-[1,2-a]pyrrole-1-carboxylic acid and the corresponding p-methoxy compound 74 were selected for evaluation as analgesic agents in humans on the basis of their high potency in the mouse phenylquinone writhing assay as well as on their minimal liability to elicit gastrointestinal erosion in rats on chronic administration. Extensive quantitative structure-activity relationship (QSAR) studies of the benzoylpyrrolopyrrolecarboxylic acids have demonstrated that the analgesic (mouse writhing) and antiinflammatory (rat carrageenan paw) potencies of these compounds are satisfactorily correlated with the steric and hydrogen-bonding properties of the benzoyl substituent(s). The 4-vinylbenzoyl compound 95, which was correctly predicted to be highly active in both assays on this basis, is undergoing advanced pharmacological evaluation in animals as a potential antiinflammatory agent.