Sapogenin-Based Molecular Switches: Design and Synthesis of Azobenzene-Linked Steroid Dimers

Herein, we report a mild and effective synthesis of steroid-azobenzene molecular switches from steroid sapogenin precursors. The strategy employs a sequence of stereospecific transformations at the C3 position, starting with an iodine-mediated substitution. A detailed analysis reveals that the reaction pathway-competitive E2 elimination vs SN2 substitution-is strictly controlled by the axial or equatorial orientation of the C3-hydroxyl group associated with the distinct A/B ring junctions. The iodinated intermediates were efficiently converted into azides, followed by the reduction to the corresponding C3 amines employing a one-pot Staudinger protocol. Final assembly with azobenzene-4,4'-dicarbonyl dichloride provided a series of dimeric conjugates. These hybrid architectures, characterized by rigid frameworks, serve as well-defined models for studying light-induced dynamics. The described methodology offers reliable access to photoresponsive steroid dimers with tunable stereochemical properties for supramolecular applications.