Diversity-Oriented Synthesis Of Steviol Glycosides And Total Synthesis Of Bioactive Flavonoid Glycosides Montbretin A

With cheap and easily available mixtures of steviol glycosides as starting materials,a practical method for steviol acquisition has been developed,on the basis of which a facile,diversity-oriented,and economic protocol for the synthesis of structurally defined steviol glycosides was established.The novel approach is featured by the highly efficient glycosylation of sterically hindered and acid-sensitive steviol via orchestrated application of Yu glycosylation,Schmidt glycosylation,and PTC glycosylation.Hence,these high-intensity sweeteners and potential lead compounds for drug development are now readily accessible.Complex flavonoid glycosides montbretin A,not only possess novel and complex chemical structures,but also have impressive antihyperglycemic activities which render them having promising medicinal future.A straightforward synthesis of Chalcone was accomplished from readily available 2,4,6-trihydroxyacetophenone monohydrate and methyl gallate,which including a series adjustments of protective group and a high efficient Aldol reaction.The hydroxy-recognition of myricetin can be obtained by reduction ring closure,OsO₄ dihydroxylation,DDQ oxidative dehydrogenation and alkaline conditions oxidative dehydrogenation from the intermediate.Next,introduction of the 3-OH trisaccharide sugar chain one by one by the Yu glycosidation.Subsequently,4'-OH MOM protection was efficiently removed in the presence of an acid-sensitive trisaccharide glycoside,and an attempt was made to introduce a sugar chain in this position.