Synthesis of C-19-functionalized 1α-hydroxyvitamin D2 analogues via ring-closing metathesis

[GRAPHICS] A heteroatom-tethered regloselective ring-closing metathesis reaction was used for the C-19 functionalization of 1alpha-hydroxy-5,6-trans-vitamin D-2 analogues. Applications of the reaction to form a range of analogues by manipulation of the tether using both organolithium reagents and Diels-Alder cycloadditions are described.