2-Aryl-5-benzoxazolealkanoic acid derivatives with notable antiinflammatory activity

The synthesis and antiinflammatory activity of 5-substituted 2-arylbenzoxazoles are described. Initial screening on carrageenin-induced rat paw edema showed that alpha-methylacetic substitution in the 5 position was preferable to substitutions with the equivalent esters, amides, alcohols, amines or tetrazoles. Halogen substitution in the aryl ring led to the most active compounds which were 2-(4-chlorophenyl)-alpha-methyl-5-benzoxazoleacetic acid (14) and 2-(4-fluorophenyl)-alpha-methyl-5-benzoxazoleacetic acid (29). These compounds were three to five times more active than phenylbutazone as assessed from ED30 values determined on rat paw edema 5 hr after single oral doses.