Synthesis and Pharmacological Characterization of Disila‐AM80 (Disila‐tamibarotene) and Disila‐AM580, Silicon Analogues of the RARα‐Selective Retinoid Agonists AM80 (Tamibarotene) and AM580

C/Si switch: Twofold sila-substitution (C/Si exchange) in the RARα-selective retinoids 1 a (AM80) and 2 a (AM580) leads to 1 b (disila-AM80) and 2 b (disila-AM580), respectively. The chemistry and biology of the C/Si pairs are reported.