Synthesis of neosaponins having an α-l-rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-d-glucopyranosyl glyco-linkage

To verify the role of the α-l-rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranosyl (chacotriosyl) moiety of steroidal glycosides from Solaum plants in their antitumor and antivirus activities, chacotriosides of diosgenin, cholesterol, and glycrrhetic acid were synthesized by developing our trans-oligoglycosidation. The chacotriosyl trichloroacetimidate was linked to the aglycones to afford neoglycosides as a mixture of α and β anomers, that was easily separated with ODS chromatography.