1α,20S-Dihydroxyvitamin D₃ Interacts with Vitamin D Receptor: Crystal Structure and Route of Chemical Synthesis

1α,20S-Dihydroxyvitamin D3 [1,20S(OH)₂D₃], a natural and bioactive vitamin D3 metabolite, was chemically synthesized for the first time. X-ray crystallography analysis of intermediate 15 confirmed its 1α-OH configuration. 1,20S(OH)₂D₃ interacts with the vitamin D receptor (VDR), with similar potency to its native ligand, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] as illustrated by its ability to stimulate translocation of the VDR to the nucleus, stimulate VDRE-reporter activity, regulate VDR downstream genes (VDR, CYP24A1, TRPV6 and CYP27B1), and inhibit the production of inflammatory markers (IFNγ and IL1β). However, their co-crystal structures revealed differential molecular interactions of the 20S-OH moiety and the 25-OH moiety to the VDR, which may explain some differences in their biological activities. Furthermore, this study provides a synthetic route for the synthesis of 1,20S(OH)₂D₃ using the intermediate 1α,3β-diacetoxypregn-5-en-20-one (3), and provides a molecular and biological basis for the development of 1,20S(OH)₂D₃ and its analogs as potential therapeutic agents.