In the imidazolyl biphenyl sulfonylurea series, effects of substitution in position 5 of the imidazole ring with enolic ketone moiety were studied on AT(2) binding. beta-ketosulfoxide, beta-ketosulfone and beta-ketoester proved to be highly effective substituents for potent nanomolar binding affinity on both AT(1) and AT(2) receptor subtypes. This led to the identification of beta-ketophenylsulfoxide RU 64276 as a potent and orally active AT(1) antagonist and AT(2) binding inhibitor.