Efficient synthesis of α- and β-chacotriosyl glycosides using appropriate donors, and their cytotoxic activity

Natural steroidal glycosides containing α-l-rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranose (chacotriose) at the oligosaccharide moiety exhibit anti-cancer and anti-herpes activities. To investigate the structure–activity relationships of the aglycone parts of chacotriosides, we developed a synthesis method for chacotriosyl glycosides having various aglycones. In the process, it was revealed that α-chacotriosyl glycosides could be obtained mainly by using a trichloroacetimidate donor, while β-chacotriosyl glycosides were afforded by using phosphite and phosphate donors. In cytotoxicity tests using the A549 and HepG2 cell lines, naturally occurring β-chacotriosyl diosgenin and cholestanol exhibited higher activities than the corresponding α-chacotriosyl glycosides.

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