Carbamate derivatives of betulinic acid and betulin with selective cytotoxic activity.

Synthesis and antiproliferative activity of eight new derivatives of betulinic acid (1) and betulin (2) are described. The compounds were tested against fifteen tumor cell lines. The toxicity against normal human fibroblasts and the mode of cell death on lung cancer cell line induced by the most active compounds 9 (bis(ethylcarbamate)betulin) and 11 (3-O-ethylcarbamate of 28-O-acetylbetulin) was investigated. Caspase 3 activity on lung cancer cell line (A549) was determined for 1, 5 (3-O-ethylcarbamate of betulinic acid), 9 and 11. All derivatives exerted a dose dependent antiproliferative action at micromolar concentrations toward target tumor cell lines. Treatment of lung cancer cells for 24h with 9 and 11 induced apoptosis, as observed by the appearance of a typical ladder pattern in the DNA fragmentation assay.