Glycosylation of panaxadiol

Glycosylation of 3 β ,12 β -dihydroxy-20 R ,25-epoxydammarane (panaxadiol) ( 1 ) under Koenigs–Knorr, Helferich, and ortho-ester reaction conditions was studied. Condensation of panaxadiol and 2,3,4,6-tetra- O -acetyl- α -D-glucopyranosylbromide ( 2 ) in the presence of silver oxide and 4-Å molecular sieves in dichloroethane gave a mixture of acetylated panaxadiol 3- and 12- O-β -D-glucopyranosides (3:1 ratio). Reaction of diol 1 and D-glucose tert -butylorthoacetate ( 3 ) in the presence of 2,4,6-collidinium perchlorate in chlorobenzene resulted in regioselective formation of panaxadiol 12- O-β -D-glucopyranoside tetraacetate. Reaction of equimolar amounts of 1 and glycosyl donor 2 in the presence of Hg(II) cyanide in nitromethane at 90°C was accompanied by opening of the tetrahydropyran ring and gave 3 β ,12 β ,25-trihydroxydammar20(22) E -ene 12- O - β -D-glucopyranoside tetraacetate. Panaxadiol 3- and 12- O - β -D-glucopyranosides and 3 β ,12 β ,25-trihydroxydammar-20(22) E -ene 12- O - β -D-glucopyranoside tetraacetate were synthesized for the first time.