A new uricosuric diuretic, S-8666, in rats and chimpanzees.

5-Dimethylsulfamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxyli c acid (S-8666) was studied as a possible new uricosuric diuretic agent using rats and chimpanzees. Various new compounds belonging to the 5-sulfamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acids were clearly diuretic with uricosuric activity in intraperitoneally oxonate-treated rats. S-8666 was chosen as a favorable candidate because its uricosuric activity due to the effects of tubular transport of uric acid were apparently more marked than those of known uricosuric agents such as probenecid, benzbromarone, tienilic acid and indacrinone in oxonate-treated rats. S-8666 was also uricosuric in rats not given urate oxidase inhibitor. The diuretic effect of S-8666 in oxonate-treated rats was as high-ceilinged as that of furosemide, while those of tienilic acid, indacrinone and a known compound of a 5-carbonyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acid were rather low-ceilinged. These uricosuric and diuretic activities of S-8666 were manifested by two enantiomers, of which the (+)-enantiomer displayed predominantly uricosuric activity and the (-)-enantiomer, diuretic activity like furosemide. The new compound was also uricosuric and diuretic in chimpanzees, although the potency of the uricosuric activity was similar to that of probenecid and less than that of indacrinone. Thus, it seems that S-8666 is a different type of uricosuric diuretic from known agents which have already been tried in humans.