| abstract |
This invention provides a simplified method for converting pregnan-3,20-dione compounds to 3α-hydroxy,3β-substituted-pregnanes. By selective use of reagents the unprotected dione is converted chemoselectively and diastereoselectively into a 3(R)-pregnan-3-spiro-2'oxirane-20-one intermediate. This intermediate can then be converted regioselectively by a second set of reactions to the 3α-hydroxy,3β-substituted-20-one form, which can be further modified at the 20-keto position. n Through this method, each ketone group is independently treated. By modifying the ketones one at a time, one can obtain the desired stereo-specificity at each site. |