| 摘要 |
<p>NEW MATERIAL:A compound expressed by formula I (R<1> is protecting group of diol; R<2> is protecting group of ketone). EXAMPLE:(2R,3S)-6,6-Ethylenedioxy-2,3-isopropylidenedioxy-5alpha-pregn an-20-one. USE:A raw material for synthesizing brassinolide and epibrassinolides. PREPARATION:The aimed compound is obtained by using 3, 20-diacetoxy- pregnan-6-one as a raw material, selectively removing only acetoxy group in the 3 position thereof by hydrolysis, etc., to afford 20-acetoxy-2-pregnan-6-one expressed by formula III, oxidizing double bond between 2- and 3-positions of the resultant compound to give diol derivative thereof, protecting the diol group to provide 20-acetoxy-pregnan-6-one derivative expressed by formula IV, protecting the ketone in the 6-position of the resultant derivative expressed by formula IV, removing the acetyl group in the 20-position thereof to afford the hydroxy derivative thereof and oxidizing the resultant hydroxy derivative to form the ketone body.</p> |
