Synthesis of dihydrodiosgenin glycosides as mimetics of bidesmosidic steroidal saponins

The focus of this work is the synthesis of bidesmosidic saponin mimetics. Therefore, dihydrodiosgenin derivatives, which differ from the natural compounds by reduction of the 22-(hemi) acetal were used as glycosyl acceptors. In preliminary studies, the dihydrodiosgenin glycosides 16, 17 and 19, as well as trisaccharide 22, were synthesized. The acceptors 10 and 14 were subjected to DMTST-mediated glucosylation for the synthesis of these-substituted compound 3. For a selective 2,4-di-rhamnosylation of the dihydrodiosgenin glucopyranoside, differentiation of the glucose OH groups was achieved by selective benzoylation with 1-(benzoyloxy)benzotriazole. Reaction of the 3,6-di-O-benzoate 32 with the perbenzoylated ethyl thiorhamnopyranoside donor 15 gave the 2,4-di-rhamnosylated compound 33, together with the mono-rhamnosylated derivative. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).