THE DISCOVERY OF POTENT NONPEPTIDE ANGIOTENSIN-II RECEPTOR ANTAGONISTS - A NEW CLASS OF POTENT ANTIHYPERTENSIVES

A new class of potent antihypertensives has been discovered that exert their effect through blockade of the angiotensin II (AII) receptor. Most AH antagonists reported so far are peptide mimics of the endogenous vasoconstrictor octapeptide angiotensin II. The compounds of this paper are nonpeptides and therefore constitute a new class of potent All receptor antagonists. Based on the overlap of a conformation of All with literature lead 3, a hypothesis was developed suggesting the need for an additional acidic functionality to increase the lead’s potency. The substitution of an additional carboxylic acid resulted in a 10-fold increase in binding affinity observed for diacid 4. The binding affinities for subsequent compounds were eventually increased 1000-fold over that of the literature leads through a systematic SAR study. Thus the All receptor binding affinity [IC50(µM)] of 15 µM for literature lead 1, for example, was increased to 0.018 and 0.012 for compounds 33 and 53. A structure-affinity relationship has been found requiring the presence of four key elements for good activity: (1) an additional phenyl ring at the N-benzyl para position of the benzylimidazole nucleus, (2) an acidic functionality at the ortho position of the terminal aromatic ring, (3) a lipophilic side chain at the imidazole 2-position of three to five carbon atoms in length, and (4) a group at the imidazole 5-position capable of hydrogen bonding. The synthesis as well as the pharmacological activity of the compounds in this new series of All receptor antagonists are presented. © 1990, American Chemical Society. All rights reserved.