Design and synthesis of a 1α,25-dihydroxyvitamin D3 dimer as a potential chemical inducer of vitamin D receptor dimerization

A dimer comprising two 1a,25-dihydroxyvitamin D₃ units linked by an alkyl side chain at C-11 was synthesized with a view to the simultaneous binding of two vitamin D receptor (VDR) molecules and the consequent induction of VDR dimerization. The short, convergent synthesis uses a stereoselective cuprate addition to introduce the linking side chain and a key ruthenium olefin metathesis as the dimerization step.