Development of silicon-containing bis-phenol derivatives as androgen receptor antagonists: Selectivity switching by C/Si exchange

We previously reported that bis-phenol derivatives, including LG190178 (3a), possess not only vitamin D receptor (VDR) agonistic activity, but also androgen receptor (AR) antagonistic activity. Here, we describe the design, synthesis and evaluation of silicon-containing bis-phenol derivatives, with the objective of obtaining increased selectivity toward VDR or AR. We found that replacement of the quaternary carbon in the bis-phenol skeleton with silicon increased AR-antagonistic activity and reduced VDR-agonistic activity, that is, the AR selectivity of the silicon-containing compounds was higher than that of corresponding carbon compounds. To our knowledge, this is the first report of nuclear receptor (NR) selectivity switching by sila-substitution (C/Si exchange). Among the compounds synthesized, AR-selective ligand (S,R)-3b exhibited more potent anti-androgenic activity (IC50 = 0.072 μM) than hydroxyflutamide, a well-known androgen antagonist (IC50 = 1.4 μM), in SC-3 cell proliferation assay. These results suggest that sila-substitution is a useful approach for structural development of selective AR ligands.