Effect of structural change on acute toxicity and antiinflammatory activity in a series of imidazothiazoles and thiazolobenzimidazoles.

The effect of structural change on the biological activity of a series of imidazothiazoles and thiazolobenzimidazoles is described. It was found that compounds with polar substituents at the 2 or 3 position of the ring system are less acutely toxic while maintaining antiinflammatory activity. Other structural changes, such as the incorporation of a gem-dimethyl substituent in the 6 position, increase acute toxicity and eliminate antiinflammatory activity. The compound with the best activity/toxicity ratio contains an alkyl sulfonyl substituent on the thiazole ring. The thiazolobenzimidazole analogues are more potent than the imidazole analogues.