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 acidderivatives 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