Abstract: To improve water solubility of betulin, two acyl groups were introduced at C-3 and C-28 hydroxy groups of betulin. 3,28-di-O-glutaryl-betulin was synthesized with pyridine as solvent and DMAP as catalyst from betulin and glutaryl anhydride. Its structure was characterized by FT-IR,¹HNMR and MS. Solubility data of betulin and 3,28-di-O-glutaryl-betulin in acetone, ethanol, water and phosphate-buffered saline (PBS, pH value 7.4) were determined by equilibrium method. The results showed that in acetone and ethanol, solubilities of 3,28-di-O-glutaryl-betulin were 33.52 and 22.65 times of those of betulin respectively; In water, solubility of 3,28-di-O-glutaryl-betulin was 0.0021g(100mL water), and in PBS, solubility of 3,28-di-O-glutary-betulin was 0.0015g (100mL PBS), the hydrophilicity of 3,28-di-O-glutaryl-betulin was significantly increase.

Key words: betulin, 28-di-O-glutaryl-betulin, synthesis, solubility property