New diphenolic azoles as highly selective estrogen receptor-beta agonists are reported. The more potent and selective analogues of these series have comparable binding affinities for ERbeta as the natural ligand 17beta-estradiol but are >100-fold selective over ERalpha. Our design strategy not only followed a traditional SAR approach but also was supported by X-ray structures of ERbeta cocrystallized with various ligands as well as molecular modeling studies. These strategies enabled us to take advantage of a single conservative residue substitution in the ligand-binding pocket, ERalpha Met(421) --> ERbeta Ile(373), to optimize ERbeta selectivity. The 7-position-substituted benzoxazoles (Table 5) were the most selective ligands of both azole series, with ERB-041 (117) being >200-fold selective for ERbeta. The majority of ERbeta selective agonists tested that were at least approximately 50-fold selective displayed a consistent in vivo profile: they were inactive in several models of classic estrogen action (uterotrophic, osteopenia, and vasomotor instability models) and yet were active in the HLA-B27 transgenic rat model of inflammatory bowel disease. These data suggest that ERbeta-selective agonists are devoid of classic estrogenic effects and may offer a novel therapy to treat certain inflammatory conditions.

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Described in this paper is the synthesis and pharmacological activity of five metabolites of the angiotensin II antagonist tasosartan (1). Of particular interest is the effect of the additional acidic group of the enol metabolite (8) on activity. As suggested by the structural-activity relationship of other angiotensin II antagonist series, a second acidic group can improve receptor binding activity but decrease in vivo activity after oral dosing. The metabolic introduction of a second acidic group in tasosartan bypasses this problem and contributes to the excellent profile of the compound. A molecular modeling study provides a rationale for the role of the enol group of 8 in AT1 receptor binding.