1,3,4-Oxadiazol-2-ylbenzenesulfonamides as privileged structures for the inhibition of monoamine oxidase B.

The present study investigates the monoamine oxidase (MAO) inhibition properties of a series of ten 5-aryl-1,3,4-oxadiazol-2-ylbenzenesulfonamides. The target compounds were synthesized by dehydration of the corresponding N,N'-diacylhydrazines with phosphorus oxychloride to yield the 1,3,4-oxadiazole cycle with concomitant transformation of the sulfonamide to the sulfonyl chloride group. Treatment with aqueous ammonia in acetonitrile regenerated the target sulfonamides. The results of the enzymology document that these compounds are potent and specific MAO-B inhibitors with the most potent compound exhibiting an IC50 value of 0.0027 µM. An analysis of the structure-activity relationships shows that the 4-benzenesulfonamides are significantly more potent MAO-B inhibitors than the corresponding 3-benzenesulfonamides, and that the corresponding N,N'-diacylhydrazine synthetic precursors are weak MAO inhibitors. Although MAO inhibition by oxadiazole compounds are known, this is the first report of nanomolar MAO inhibition potencies recorded for sulfonamide derivatives. MAO-B specific inhibitors such as those discovered here may be of interest in the treatment of neurodegenerative disorders such as Parkinson's disease.