135041-04-2Relevant articles and documents
Convergent synthesis of vitamin D3 metabolites. Control of the stereoselectivity in samarium-induced cyclopropanations of cyclopentenes
Kabat,Kiegiel,Cohen,Toth,Wovkulich,Uskokovic
, p. 118 - 124 (1996)
The 25-hydroxy and 1α,25-dihydroxy vitamin D3 metabolites are obtained by solvolytic rearrangements of the 1-desoxy and 1α-hydroxy cyclopropyl vinylogous alcohols 31 and 29, respectively, with simultaneous formation of the vitamin D structural triene and the 3-hydroxy function. Two complementary methods have been employed to direct the stereoselectivity of the samarium induced olefin cyclopropanations which ultimately lead to key chiral ring A precursors. One protocol uses the two stereogenic centers of the (R,R)-2,3-butanediol ketal moiety of 8, while the other method uses the allylic hydroxyl group of (R)-16.
Control of stereoselectivity in samarium metal induced cyclopropanations. Synthesis of 1,25-Dihydroxycholecalciferol
Kabat,Kiegiel,Cohen,Toth,Wovkulich,Uskokovic
, p. 2343 - 2346 (2007/10/02)
1,25-Dihydroxycholecalciferol (23) was synthesized from A-ring precursor 18 and Windaus-Grundmann ketone 19 via cyclovitamin D 21. Key reactions include highly stereoselective (5 to 6) and stereospecific (13 to 14) cyclopropanations.
