Synthesis Of N-nucleosides, C-nucleosides, Daphnodorin B And Gensenosides

1. Synthesis of nuclosides with glycosyl trifluoroacetimidates as donorsNucleosides are the basic raw materials of synthesis of oligonucleotides and gene fragments. Analogs of nucleosides and nucleotides used as therapeutic agents play an important role in the Chemical drugs. We synthesied a series of furan and pyran-type N- and O-glucosides with glycosyl trifluoroacetimidates as donors and BSA or BSTFA as the silane reagent under the catalyst of TMSOTf. Via carafully solvent screening, a high efficient“one-pot”procedure for nucleosides synthesis was also achieved.2. Syntheses of Daphnodorin B and C-nucleosidesDaphnodorin B which has a good activity of anti-bacterial, anti-tumor and anti-HIV-1 is a kind of flavonoids isolated from the root of a traditional Chinese medicine Frangrant Daphne. Starting from 2,4,6-trihydroxyacetophenone and p-hydroxybenzaldehyde, we synthesised the fully protected Daphnodorin B in a linear 14-step and the yield of 10.3%, in which some key reactions such as Aldol condensation, Sharpless asymmetric hydroxylation, Micheal addition and palladium-catalyzed Heck reaction were invovled. We also devised a new method, which has been proved to enjoy a broad scoup, for the synthesis of benzofuran ring via a Micheal addition followed by the palladium-catalyzed Heck reaction. We also reported that O-glycosides existed as a enol form can be rearranged to C-glycosides under the catalyst of Sc(OTf)3. A new method for the synthesis of C-Nucleosides through direct C-glycosylation ofβ-diketone derivatives with 1-OH sugars under catalyst of InCl3 was demonstrated too.3. Synthesis of Ginsenoside Rh2, Chikusetsusaponin-LT8 and Chikusetsusaponin L10 via Gold(I)-catalyzed glycosylation with glycosyl ortho-Alkynylbenzoates as donorsGinseng which was known as“King of Herbs”has a very high medicinal value. Ginsenosides are considered as the main active ingredients in Ginseng. Starting from the Protopanaxadiol and Protopanaxatriol isolated from the total extract of P.ginseng, the activity of the hydroxyl groups was successfully distinguished. Base on the research, we also reported the concise synthesis of three ginsenosides: that is Ginsenoside Rh2, Chikusetsusaponin-LT8 and Chikusetsusaponin L10 via Gold(I)-catalyzed glycosylation of Protopanaxadiol and Panaxatriol derivatives with glycosyl ortho-Alkynylbenzoates as donors. Meanwhile, a lot of studies on the glycosylation of 20-hydroxy group had been done.