Etodolic acid and related compounds. Chemistry and antiinflammatory actions of some potent di- and trisubstituted 1, 3, 4, 9-tetrahydropyrano[3, 4-b]indole-1-acetic acids.

A series of 37 1-ethyl- and 1-n-propyl-1, 3, 4, 9-tetrahydropyrano[3, 4-b]indole-1-acetic acids bearing one, or two, substituents on the benzene ring has been synthesized via the acid-catalyzed condensation of a substituted tryptophol with ethyl propionylacetate or ethyl butyrylacetate. Antiinflammatory and ulcerogenic effects were examined and the results show that 1, 8-diethyl-1, 3, 4, 9-tetrahydropyrano[3, 4-b]indole-1-acetic acid (etodolic acid, USAN) is a potent agent, particularly active against a chronic rat model of inflammation (ED50 0.7 + 1-0.1 mg/kg po in the adjuvant arthritis model) and which has a relatively low acute ulcerogenic potential in the same species.