Chemical Synthesis and Biological Activities of 20S,24S/R-Dihydroxyvitamin D3 Epimers and Their 1α-Hydroxyl Derivatives.

Bioactive vitamin D3 metabolites 20S,24S-dihydroxyvitamin D3 [20S,24S(OH)2D3] and 20S,24R-dihydroxyvitamin D3 [20S,24R(OH)2D3] were chemically synthesized and confirmed to be identical to their enzymatically generated counterparts. The absolute configurations at C24 and its influence on the kinetics of 1α-hydroxylation by CYP27B1 were determined. Their corresponding 1α-hydroxyl derivatives were subsequently produced.