A short practical approach to 24R,25-dihydroxyvitamin D3

Abstract A synthesis of the vitamin D 3 metabolite 24 R ,25-dihydroxyvitamin D 3 ( 1 ) by Lythgoe's Wittig–Horner approach is described. The key step of the synthesis is the stereocontrolled introduction of the 24-hydroxyl group by a palladium(0)-induced [3,3]-sigmatropic rearrangement on a 22 R -allylic acetate ( 7 ).