Betulin ketoacetic acid in the form of a white crystalline powder is a pentacyclic triterpenoid widely distributed in a variety of plants, and its content in the bark of Betula alba ranges from 0.25 to 2% (in dry form).
(+)-Betulonic Acid shows potent cytotoxic activities against PC3, MGC-803, Bcap-37, and MCF-7 cell lines.
General procedure for the synthesis of 3-oxo-lupin-20(29)-en-28-oic acid from betulinic acid:
1. preparation of Jones' reagent: chromium trioxide (CrO3, 26.72 g) was dissolved in concentrated sulfuric acid (H2SO4, 23 ml) and the solution was subsequently diluted to 100 ml with water.
2. Reaction process: Betulinic acid (BA, 500 mg, 1.09 mmol) was dissolved in a solvent mixture of dichloromethane (CH2Cl2, 12 ml) and acetone (12 ml), and Jones reagent (1 ml) was added slowly after cooling.
3. Reaction control: the reaction mixture was stirred at room temperature for 15 min followed by addition of methanol (MeOH, 5 ml) to terminate the reaction. After continued stirring for 10 minutes, the reaction mixture was diluted by adding dichloromethane (CH2Cl2, 20 ml).
4. Post-treatment: The organic layer was washed sequentially with water and saturated sodium chloride (NaCl) solution, dried with anhydrous sodium sulfate (Na2SO4) and subsequently concentrated under vacuum.
5. Purification: the crude product was recrystallized three times in methanol (MeOH) to give 3-oxo lupin-20(29)-en-28-oic acid (462 mg, 93% yield) as a white solid.
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