5-sulfamoylorthanilic acids, a sulfonamide series with salidiuretic activity

A series of 4,N-disubstituted 5-sulfamoylorthanilic acids was synthesized by nucleophilic substitution reactions starting either from 2,4-dihalogeno-5-sulfamoylbenzenesulfonic acids or, in most cases, from phenyl 2,4-dihalogeno-5-sulfamoylbenzenesulfonates. The latter method is based on the relative stability of the phenoxysulfonyl group to nucleophiles, e.g., amines, phenols, and thiols, and the possibility of smooth hydrolytic or hydrogenolytic cleavage as a final step, with formation of the SO3H group. On evaluation of these compounds for salidiuretic activity in rats orally (po), and in dogs orally and intravenously (iv), a number of highly active substances was found; the best had a threshold dose of 0.02 mg/kg po in dogs. The results are given in tables, and the structure-activity relationships within the series are discussed. Besides the known effect of the phenoxy radical, an outstanding activating effect was shown by the butylsulfonyl and cycloalkylsulfonyl radicals and by the N-methylanilino radical in particular when they were located in the 4-position of the orthanilic acid molecule. The sulfanilic acid isomers corresponding to three of the most active compounds were synthesized and proved to be completely inactive in rats.