Efficient Total Synthesis Of Diverse Protopanaxadiol-type Ginsenosides

As listed in the literature, ginsenosides are considered as the main active ingredients in Ginseng. The pharmacological effects or the boilogical activities of ginseng, which have been reported, including: anti-aging activity, anti-diabetic activity, immunoregulatory activity, anti-cancer activity, neuroregulation activity, wound and ulcer healing activity, etc. Limited by the isolation and identification conditions, so the activity of ginsenosides mainly rely on the pure products that separated and purificated from the total saponins of Panax ginseng, but it is extremely difficult to separate and purificate of them. The demands of biological activity tests and pharmacological studies of ginsenosides are larger. Thus, an efficient approach to generate ginsenosides and their analogues is urgently needed.Until now, the composition of monosaccharide in the natural ginsenosides which had been isolated and identified are beta configurations, however, they often contain disaccharides or polysaccharides(1?6), Absolute configuration in the glucosidation are usually undefined because of lack of anchimeric assistance, and glycoside configurations formed in the products are usually ?-anomers. So far, there is no effective methods have been reported in this aspect. In this stud, we had tried to construct a ?-anomer with the disaccharides(1?6) using of the convergence-synthesis method, a variety of different active glycosyl donors with different protecting groups were synthesized. Glycosylation reactiond had been tried with different catalysts, in different organic solvent with various polarities, and at different temperatures, Unfortunately, all the conditions are not achieved the inversion of the proportion of ?- and ?-anomers products. Then, we adjusted the synthetic strategy. By using of the protopanaxadiol isolated from the total extract of P.ginseng, and glycosyl ortho-hexynyl- benzoates as donors under the catalysis of PPh3AuNTf2, we report the first synthesis of Ginsenoside C-K, Rh2, Rb1, Rd in a linear synthesis strategy.An synthesis method for ginsenosides based on an easily available and cheap resource was explored. It will lay a solid foundation for the establishment of ginsenosides compounds library, and it could be studied further on the structure- activity relationship of ginsenosides, so as to tap the compounds which have medicinal potentials.