| 摘要 |
<p>PURPOSE:To obtain the titled compound which is an intermediate for active vitamin D3 in high yield, by using a hydroxycholest-5-ene wherein the hydroxyl group is protected with a specific protective group as a raw material. CONSTITUTION:A hydroxycholest-5-ene of formula I (R1 and R2 are lower alkoxycarbonyl groups; R3 and R4 are Hs or lower alkoxycarbonyloxy groups) is reacted with a brominating agent capable of brominating the allyl position and then a dehydrobrominating agent to give a hydroxycholesta-5,7-diene of formula II. The hydroxyl group of the hydroxycholest-5-ene protected with a lower alkoxycarbonyl group, e.g. ethoxycarbonyl group, reduces the formation of by-products and facilitates the separation and purification.</p> |
