Synthesis and anti-cancer activity of a glycosyl library of N-acetylglucosamine-bearing oleanolic acid.

N-Acetylglucosamine-bearing triterpenoid saponins (GNTS) were reported to be a unique type of saponins with potent anti-tumor activity. In order to study the structure-activity relationship of GNTS, 24 oleanolic acid saponins with (1 --> 3)-linked, (1 --> 4)-linked, (1 --> 6)-linked N-acetylglucosamine oligosaccharide residues were synthesized in a combinatorial and concise method. The cytotoxicity of these compounds toward the leukemia cell line HL-60 and the colorectal cancer cell line HT-29 could not be improved. Half maximal inhibition below 10 μM was achieved in one single case. The study revealed that the activity decreased following the order of 3' > 4' > 6' glycosyl modifications. GNTS that incorporated (D/L)-xylose and L-arabinose at positions 3' and 4' were more potent than those bearing other sugars.