Synthesis and SAR studies of novel triazolopyrimidine derivatives as potent, orally active angiotensin II receptor antagonists.

The synthesis and pharmacological activity of new nonpeptide angiotensin II (AII) receptor antagonists are presented. These [1,2,4]-triazolo[1,5-c]pyrimidine and 1,2,4-triazolo[4,3-c]pyrimidine derivatives represent a new class of bicyclic antagonists that produced a potent, oral antihypertensive activity in the renal artery-ligated rat model. In vitro, they displayed a high affinity for rat adrenal AII receptors and were found to be specific for the AT1 receptor subtype. A SAR study has shown the importance of the 8-[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl for oral activity and the critical role of alkyl substituents at 5- and 7-positions. No significant differences were found between the [1,5-c] and [4,3-c]series. UP 269-6 (5-methyl-7-n-propyl-8-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl ]- [1,2,4]-triazolo[1,5-c]pyrimidin-2(3H)-one, derivative 29) was selected as the lead compound. It was shown to be a highly potent antihypertensive derivative (decrease in mean arterial pressure of 39.6 +/- 7.2 mmHg at 1 mg/kg po in renal artery-ligated rat) with a long duration of action which displayed a high affinity for adrenal AII receptors with a marked selectivity for the AT1 receptor subtype (Ki AT1 = 24 nM; Ki AT2 = 79,200 nM). This compound is currently undergoing extensive pharmacological and clinical development.