VitaminD3 active metabolites 24R,25-(OH)2-D3, 24S,25-(OH)2-D3, and 1 alpha, 24R,25-(OH)3-D3 were synthesized by a convergent and stereoselective approach. In the synthetic route, the stereogenic center at C-24 was generated through ultrasonically induced aqueous conjugate addition of iodide 6 to Seebach's dioxolanone 5, and the vitamin D triene system was constructed using the Lythgoe approach. The
side-chain-hydroxylated D3derivatives was explored. We found that the 24R and 26R metabolites were more effectively hydroxylated at C1 by CYP27B1 compared to the corresponding S diastereomers. However, CYP27B1 showed almost no activity towards either of the diastereomers of the 23-hydroxylated derivative. This is the first report to show that CYP27B1 metabolizes 26-hydroxylated D3, converting 25,26D3