Ring nitrogen-substituted non-steroidal estrogens: pyridine and pyrimidine analogs of the phenol in deoxyhexestrol experience resonance constraints on preferred ligand conformation

Synthesis and structure-activity relationships of 1-benzylindane derivatives as selective agonists for estrogen receptor beta

The estrogen receptor beta (ERβ) selective agonist is considered a promising candidate for the treatment of estrogen deficiency symptoms in ERβ-expressing tissues, without the risk of breast cancer, and multiple classes of compounds have been reported as ERβ selective agonists. Among them, 6-6 bicyclic ring-containing structures (e.g., isoflavone phytoestrogens) are regarded as one of the cyclized analogues of isobutestrol 5b, and suggest that other cyclized scaffolds comprising 5-6 bicyclic rings could also act as selective ERβ ligands. In this study, we evaluated the selective ERβ agonistic activity of 1-(4-hydroxybenzyl)indan-5-ol 7a and studied structure-activity relationship (SAR) of its derivatives. Some functional groups improved the properties of 7a; introduction of a nitrile group on the indane-1-position resulted in higher selectivity for ERβ (12a), and further substitution with a fluoro or a methyl group to the pendant phenyl ring was also preferable (12b, d, and e). Subsequent chiral resolution of 12a identified that R-12a has a superior profile over S-12a. This is comparable to diarylpropionitrile (DPN) 5c, one of the promising selective ERβ agonists and indicates that this indane-based scaffold has the potential to provide better ERβ agonistic probes.

Phenethyl pyridines with non-polar internal substituents as selective ligands for estrogen receptor beta

To create estrogen receptor beta (ERbeta)-selective ligands with improved biological characteristics, we have extended our investigations of structurally simple bibenzyl-core ligands by preparing a series of compounds in which one phenol is replaced by a 3-hydroxypyridine ring. These phenethyl pyridines were obtained by picoline anion alkylation, and compounds with different patterns of alkyl substitution on the central two carbon units were prepared. Binding affinities for ERalpha and ERbeta were determined, and ligands with promising affinities and selectivities for ERbeta were further tested for their gene transcriptional activity. Several compounds had high affinity selectivity and good potency selectivity in transcription assays. This study advances our understanding of compounds having ER-subtype selectivity and will help to direct efforts in developing novel ER ligands.

Bibenzyl- and stilbene-core compounds with non-polar linker atom substituents as selective ligands for estrogen receptor beta

A series of structurally simple bibenzyl-diol and stilbene-diol core molecules, structural analogs of the well-known hexestrol and diethylstilbestrol non-steroidal estrogens, were prepared and evaluated as estrogen receptor (ER) subtype-selective ligands. Analysis of their ERalpha and ERbeta binding showed that certain substitution patterns engendered binding affinities that were >100-fold selective for ERbeta. When further investigated in cell-based gene transcription assays, some molecules showed similarly high relative transcriptional potency selectivity in favor of ERbeta. Interestingly, the most ERbeta-selective molecules were those bearing non-polar substituents on one of the internal carbon atoms. These compounds should be useful probes for determining the physiological roles of ERbeta, and they might lead to the development of more selective and thus safer pharmaceuticals.