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The synthesis and structure-activity relationship (SAR) studies of a series of 4'-oxazolyl-N-(3,4-dimethyl-5-isoxazolyl)[1, 1'-biphenyl]-2-sulfonamide derivatives as endothelin-A (ET(A)) receptor antagonists are described. The data reveal a remarkable improvement in potency and metabolic stability when the 4'-position of the biphenylsulfonamide is substituted with an oxazole ring. Additional 2'-substitution of an acylaminomethyl group further increased the binding activity and provided one of the first subnanomolar ET(A)-selective antagonists in the biphenylsulfonamide series (17, ET(A) K(i) = 0.2 nM). Among the compounds described, 3 (N-(3,4-dimethyl-5-isoxazolyl)-4'-(2-oxazolyl)[1, 1'-biphenyl]-2-sulfonamide; BMS-193884) had the optimum pharmacological profile and was therefore selected as a clinical candidate for studies in congestive heart failure.

Random screening of compounds in an ETA receptor binding assay led to the discovery of a class of benzenesulfonamide ligands. Optimization led to the development of 5-amino-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesulfonamides which were functional antagonists. Structural features which were important to activity included a 1,5-substitution pattern on the naphthalene ring; a sulfonamide NH with a pK value < 7; an amine, preferably with alkyl substituents, at the 5-position; and methyl groups on both the 3- and 4-positions of the isoxazole.

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