Synthesis of a chlorogenin glycoside library using an orthogonal protecting group strategy

Naturally occurring spirostanol saponins bear a chacotriose, α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→4)] -β-d-glucopyranose residue as the oligosaccharide moiety which is believed to be important for biological activity. Herein the development of a concise, combinatorial method for the synthesis of two series of glycan variants at the 2′ and/or 4′ positions of chacotriose is described and the structure-activity relationships of the glycone part at 3-OH of chlorogenin investigated. These compounds were found to be weakly-cytotoxic toward leukemia cell lines CCRF and HL-20, indicating that the chacotriose moiety is important for anticancer activity.