Direct Glycosylation Of Oximes And Synthesis Of Ginsenoside Rb2 With The Gold(Ⅰ)-Catalyzed Glycosylation Reaction

1. Highly Efficient Construction of Hydroxylamino Glycosidic Linkages via Direct Glycosylation of Oximes with Glycosyl ortho-Akynylbenzoates as DonorsThe gold (Ⅰ)-catalyzed glycosylation reaction with ortho-alkynylbenzoates as donors has recently been proven to be a versatile method for the synthesis of various glycosidic linkages. By using glycosyl ortho-hexynylbenzoates as donors under the catalysis of PPh3AuOTf, direct glycosylation of sugar oximes and HONHFmoc has been realized for the first time, providing an effective approach to the synthesis of N-O linked saccharides, which are of great biological interest.2. Synthesis of Ginsenoside Rb2The major active principles in ginseng are recognized to be the dammarane glycosides, which indeed have shown numerous pharmacological activities, including immunostimulatory, antiatherosclerotic, antihypertensive, antidiabetic, anticarcinogenic, and CNS protective activities. Ginsenoside Rb2 representing the most complex type protopanaxadiol ginsenosides. By using glycosyl ortho-hexynylbenzoates as donors under the catalysis of PPh3AuNTf2, we report the first synthesis of Ginsenoside Rb2.3. Total Synthesis study of Echiniside ASea cucumber saponins are secondary metabolites produced by holothurians. Structurally, they are triterpene glycosides that play an important role in chemical defense and possess a wide spectrum of pharmacological effects, including antiviral, antifungal, antitumor, immunomodulatory, cytotoxic, hemolytic. Echinoside A exhibits broad spectrum antitumor activity both in vitro and in vivo. Using (+)Wieland-Miescher Ketone as starting material, we tried Diels-Alder reaction and Robinson annulation to construct the key skeleton of Echinoside A. This work is still in progress.