Pyrido[2,3-d]pyrimidine Angiotensin II Antagonists

A series of pyrido[2,3-d]pyrimidine angiotensin II (A II) antagonists was synthesized and tested for antagonism of A II. Compounds with a biphenylyltetrazole pharmacophore and small alkyl groups at the 2- and 4-positions of the pyridopyrimidine ring were found to be the most potent in an AT1 receptor binding assay and in blocking the A II pressor response in anesthetized, ganglion-blocked A II-infused rats. 5,8-Dihydro-2,4-dimethyl-8-[(2'-(1H-tetrazol-5-yl) [1,1'-biphenyl]-4-yl)methyl]pyrido[2,3-d]pyrimidin-7(6H)-one (4a) was one of the more potent compounds in the binding assay and was the most efficacious compound in the A II-infused rat model. Further study of 4a in Goldblatt (2K-1C) rats showed the compound to have oral bioavailability and to be an efficacious and potent compound in a high renin form of hypertension.