| abstract |
The present invention provides a method for preparing an ester of betulin at the 3-position, e.g., betulin-3-acetate, including the selective alcoholysis of a betulin-3,28-diester, e.g., betulin-3,28-diacetate; a method for preparing betulin-3-acetate including (1) acetylating betulin to provide betulin-3,28-diacetate and (2) the alcoholysis of betulin-3,28-diacetate to provide betulin-3-acetate; and a method for preparing betulinic acid (1) acetylating betulin to provide betulin-3,28-diacetate, (2) the alcoholysis of betulin-3,28-diacetate to provide betulin-3-acetate, (3) oxidizing betulin-3-acetate to provide betulinic aldehyde-3-acetate, (4) oxidizing betulinic aldehyde-3-acetate to provide betulinic acid-3-acetate, and (5) deprotecting betulinic acid-3-acetate to provide betulinic acid. |