Synthesis of 2β-substituted-14-epi-previtamin D3 and testing of its genomic activity

2β-Substituted analogs of 14-epi-previtamin D3 were synthesized for the first time by the thermal isomerization of the corresponding 14-epi-vitamin D3 that were available using coupling reaction between the A-ring phosphine oxide derived from a chiral epoxide and CD-ring cis-hydrindanone. The VDR binding affinity and transactivation activity of osteocalcin promoter in HOS cells were evaluated, and the new analogs were found to be less active, 0.01–0.18% of VDR binding affinity compared with the natural hormone and EC50 1.0–9.1 nM for transactivation activity, than 14-epi-previtamin D3 with 0.5% (VDR) and EC50 0.46 nM, respectively.