3,28-Bis-O-polyfluorobenzoylbetulin. Synthesis, Molecular Structure, and Cytotoxicity

Treatment of betulin with 2,3,4,5-tetrafluoro- and pentafluorobenzoyl chlorides in triethylamine afforded 3,28-bis- O -polyfluorobenzoylbetulins. According to the X-ray diffraction data, all six-membered rings in the 3,28-bis- O -pentafluorobenzoylbetulin molecule appear in a chair conformation, and the five-membered ring has an envelope conformation with the C 17 atom deviating from the plane formed by the other four carbon atoms. Unlike betulin itself, the obtained bis-esters showed no cytotoxic effect on human lung adenocarcinoma cell line A549 and human glioblastoma cell line U251.