Stereoselective syntheses of 20-epi cholanic acid derivatives from 16-dehydropregnenolone acetate
作者:Bapurao B. Shingate、Braja G. Hazra、Vandana S. Pore、Rajesh G. Gonnade、Mohan M. Bhadbhade
DOI:10.1016/j.tet.2007.04.014
日期:2007.6
A stereoselective total synthesis of naturally occurring 20-epi cholanic acid derivatives has been realized, starting from readily available 16-dehydropregnenolone acetate. The key step of these syntheses involves an ionic hydrogenation of a C-20,22-ketene dithioacetal and deoxygenation of steroidal C-20 tert-alcohols, to set up the unnatural C(20R) configuration with 100% stereoselectivity. The unnatural
从容易获得的16-脱氢孕烯醇酮乙酸酯开始,已经实现了天然存在的20-表位胆酸衍生物的立体选择性全合成。这些合成的关键步骤涉及C-20,22-烯酮二硫缩醛的离子加氢和甾体C-20叔醇的脱氧,以100%的立体选择性建立非天然的C(20 R)构型。如此获得的具有C(20 R)立体中心的非天然C-22醛被精制为20-表位胆酸衍生物。20- Epi的两个导数合成了胆酸,并通过单晶X射线分析证实了其结构。在乙醇中对16-脱氢孕烯醇酮乙酸酯和16-脱氢孕烯醇酮进行催化加氢,得到C-5,C-16四氢产物。这些产物之一的晶体结构分析显示氢原子的C-5α和C-17α构型。