Glycosylation of 6 alpha,12 beta-dihydroxy-20R,25-epoxydammaran-3-one

摘要

Glycosylation of 6 alpha,12 beta-dihydroxy-20R,25-epoxydammaran-3-one (panaxatriol 3-ketone, 2) under Koenigs-Knorr reaction conditions and the Helferich modification was studied. Condensation of 2 with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosylbromide (5) in the presence of Ag2O and 4- molecular sieves in CH2Cl2 gave acetylated 6 alpha,12 beta-dihydroxy-20R,25-epoxydammaran-3-one 12-O-beta-D-glucopyranoside whereas in the presence of Hg(CN)(2) in nitromethane at 25A degrees C the tetrahydropyran ring opened and, depending on the ratio of reagents, acetylated 12-, 12,25-di-, or 6,12,25-tri-O-beta-D-glucopyranosides of 6 alpha,12 beta,25-trihydroxydammar-20(22)E-en-3-one formed. 6 alpha,12 beta-Dihydroxy-20R,25-epoxydammaran-3-one 12-O-beta-D-glucopyranoside and 12-, 12,25-di-, and 6,12,25-tri-O-beta-D-glucopyranosides of 6 alpha,12 beta,25-trihydroxydammar-20(22)E-en-3-one were synthesized for the first time.