Metathesis reactions of Delta(22)-steroids are studied. The cross metathesis reactions of model Delta(22)-steroids with excess of simple alkenes are sluggish or do not occur at all. In contrast, derivatives of both trans- and cis-Delta(22)-cholesterol undergo ring closing metathesis reactions but the former reacts faster. However, the side chain double bond in stigmasterol and ergosterol is too crowded for metathesis reactions promoted by currently available catalysts. (C) 2009 Elsevier Ltd. All rights reserved.
The synthesis and the mass and nuclear magnetic resonance spectra of side chain isomers of cholesta-5,22-dien-3β-ol and cholesta-5,22,24-trien-3β-ol
作者:Roderick F.N. Hutchins、Malcolm J. Thompson、James A. Svoboda
28-Norbrassinolide (2α, 3α, 22R, 23R-tetrahydroxy-B-homo-7-oxa-5α-cholestan-6-one), which is an analog of the plant growth promoting steroidal lactone, brassinolide, was synthesized via 22R, 23R-dihydroxycholesterol. Syntheses of the other C-22, 23 stereoisomers of 22, 23-dihydroxycholesterol were also described.