Synthesis, Crystal Structure Analysis, and Pharmacological Characterization of Disila-bexarotene, a Disila-Analogue of the RXR-Selective Retinoid Agonist Bexarotene

Twofold sila-substitution (C/Si exchange) in the saturated ring of the tetrahydronaphthalene skeleton of the RXR-selective retinoid agonist bexarotene ( 1a ) leads to disila-bexarotene ( 1b ). Compound 1b was synthesized in a multistep synthesis, starting from 1,2-bis(chlorodimethylsilyl)ethane. The identity of 1b was established by elemental analyses and multinuclear NMR studies, and the C/Si analogues 1a and 1b (and an intermediate in the synthesis of 1b ) were structurally characterized by single-crystal X-ray diffraction. Furthermore, 1a and 1b were studied for their interaction with retinoid X receptors. Although the twofold sila-substitution of 1a resulted in significant differences in the molecular structures of 1a and 1b, disila-bexarotene ( 1b ) was shown to be a highly potent RXR agonist.