| 摘要 |
<p>PURPOSE:To obtain the title compound which is an intermediate for the active vitamin D3 analogs advantageously, by using inexpensive lithocholic acid easily available in a large quantity as a starting material. CONSTITUTION:Easily available lithocholic acid of formula I is esterified with a lower alkanol, oxidized with Jone's reagent to give a compound of formula II, which is reacted with 2-methyl-2-ethyl-1,3-dioxolan, hydrogenated with LiAlH4, and oxidized to form a compound of formula III. The resulting compound is reacted with (C6H5)3P=C (CH3)2, oxidized with an organic peracid, and hydrolyzed with an acid to form a compound of formula IV, which is diacylated, and dehydrogenated to have a double bond introduced. The protecting groups are eliminated to give 24xsi, 25-dihydroxy-cholesta-1,4,6-trien-3-one (D) of formula V in an overall yield >= about 5.5%. 1, 24xsi, 25-Trihydroxycholecaciferol can be derived from D.</p> |
