99-32-1

95-92-1

67-64-1

99-32-1

A modified literature method was used to synthesize betulinic acid from diethyl oxalate and acetone. The steps were as follows: in a typical experiment, sodium ethoxide (69.4 g, 1.02 mol) was suspended in ethanol (300 mL). After stirring at 60 °C for 45 min, a mixed solution of anhydrous acetone (29 g, 38 mL, 0.5 mol) and diethyl oxalate (155 g, 144 mL, 1.06 mol) was slowly added dropwise. After the dropwise addition, the reaction temperature was maintained at 60 °C and the reaction continued to be stirred for 14 hours. Subsequently, 37% aqueous hydrochloric acid solution (230 mL) and water (100 mL) were added to the reaction mixture and the reaction was stirred for 24 h. After 24 h, about half of the aqueous ethanol was evaporated under reduced pressure, and water (300 mL) and 37% aqueous hydrochloric acid solution (60 mL) were then added to the remaining mixture, and the stirring was continued at 50 °C for 20 h. The reaction was completed by filtration and the mixture was collected. Upon completion of the reaction, the resulting solid was collected by filtration and washed sequentially with water and acetone. The resulting solid was recrystallized using activated carbon in boiling water. The filtrate was allowed to stand at room temperature until crystals precipitated. The white crystals were collected and dried under vacuum to give the final target product leucocholic acid (42.3 g, 46% yield).