In order to evaluate the role of the 6-OH group in madecassic acid on the cytotoxicity to HepG2 cells, a series of the conjugates 15-18 were synthesized (Scheme 2). Triacetyl madecassic acid was first treated with thionyl chloride in the presence of pyridine to give the dehydrated compound 14 in 47% yield after a silica gel column chromatography. In a similar two-step sequence reaction, conversion of the acid 14 into the intermediate chloride acid followed by coupling with amino acids (glycine; or β-alanine), and subsequently esterified with silybin (1) under Steglich conditions provided esters 15-16 . Treatment of these esters with acetic anhydride provided products 17 and 18 in 68% and 58% yields, respectively, after silica gel column chromatography (Scheme 2).