Syntheses Of Echinocystic Acid,Qullaic Acid And Acacic Acid Lactone

As an important subgroup of triterpen saponins,D/E-ring-functionalized oleanane-type saponins have been proven to possess a diversity of bioactivities including antitumoral,hypoglycemic,and pancreatic lipase-inhibitory activities,thus having the promise to be pharmaceutically applied.Impeded by the difficult access of the D/E-ring-functionalized oleanane-type aglycons,the development of D/E-ring-functionalized oleanane-type saponins synthesis proceeds sluggishly,which retards the pharmaceutical application process of these valuable compounds.Compared with the mature modification of oleanolic triterpene saponins A ring,the syntheses of D/E ring functionalized saponins are still a difficult bottleneck to break through.In this paper,the synthesis of Echinocystic acid and Qullaic acid was completed,with the synthetic of Acacic acid lactone and the glycosidation of saponin acid at C-3 position were preliminarily explored.As a result,the D,E ring of oleanolic acid was preliminarily modified.1.The synthesis of Echinocystic acidThe raw material was prepared with nearly twice the extraction efficiency?217mg/g?of the literature,and the activation of six hydroxyl groups in the structure were identified.Finally,the linear step was converted to a yield of 4.27%.On the other hand,it was selective deoxyged at the position of C-21.The deoxygenation routes at C-21 and C-22 sites in the synthesis process provide a new idea for the modification of D,E rings of oleanolic triterpene saponins in the future.2.The synthesis of Qullaic acidWith the aid of 3-OH,the hydroxyl group was introduced at the C-23 position by C-H activation,and the synthesis from Echinocystic acid to Qullaic acid was completed in a linear 9-step with 20.65%yield.Also the 3-OH glycosidation was explored by model reaction.At final,it yielding a high yield,with only the results of the?-configuration product.Laid a good foundation for the subsequent completion of the synthesis and modification of QS-21.3.Exploratory study on Acacic acid lactoneAs a hexacyclic triterpene containing a lactone ring,Acacic acid lactone is a special class of D/E ring functionalized oleanane triterpenoid saponins.In the process of synthesis and exploration,the SmI₂ could selectively reduction the hydroxyl at C-22 position,which was an important prerequisite for closing the lactone ring.