Design, semisynthesis and cytotoxic activity of novel ester derivatives of betulinic acid-1,2,4 oxadiazoles.

Taking into consideration of the biological activity of betulinic acid derivatives containing a oxadiazole ring, the semisynthetic betulinic acid-1,2,4-oxadiazole esters (14-25) were synthesized starting from betulinic acid (1) and 5-(bromomethyl)-3-aryl-1,2,4-oxadiazoles (2-13) and final compounds were tested for cytotoxic activity on three human cancer cell lines in vitro. All tested compounds showed good cytotoxic activity. The structures of synthesized compounds are established based on infrared (IR), nuclear magnetic resonance (NMR), and mass spectrometry.