(Acylaryloxy)acetic acid diuretics. 4. Indeno[5,4-b]furan-2-carboxylic acids

Investigation of the chemistry of the potent new uricosuric diuretic indacrinone (MK-196) led to a class of novel annulated derivatives, indeno[5,4-b]furan-2-carboxylic acids. The structural requirements for optimal diuretic and uricosuric activity of the tricyclic analogues differed from those of their (indanyloxy)acetic acids counterparts. Most notably, the tricyclic analogues were two to four times more natriuretic than the corresponding (indanyloxy)acetic acids when administered orally to rats, and in chimpanzees, uricosuria was observed only in those indenofurans having a nuclear aryl substituent.