Preparation Of Glycosyl Carboxylic Acids By Oxidation Of Corresponding C-glycosides

As a special kind of carbohydrates,glycosyl carboxylic acids have a wide range of applications in glycoschemistry and glycosbiology.However,the classical synthesis methods of glycosylcarboxylic acids have significant limitations: i)they require the use of highly toxic cyanide reagents and heavy metal salts;ii)the reaction conditions are harsh,and the functional group tolerance and substrate compatibility are poor;iii)they can only be used to synthesize 1,2-trans carboxylic acids.In this thesis,we developed a new method for glycosyl carboxylic acid based on the oxidation reactions of C-aryl/vinyl glycosides,which is divided into the following two parts:In the second chapter,we took glycosyl bromide as raw material and obtained various C-aryl glycosides through multi-step reactions.Subsequently,various glycosyl carboxylic acids were successfully obtained by using Sharpless oxidation reaction.Then the effect of the electrical distribution of aryl substrate on the oxidation reaction was studied.Finally,Scleropentaside A was successfully synthesized using Liebeskind-Srogl coupling reaction as a key step.However,this method requires large excess of sodium periodate and not compatible electron-rich protecting group(e.g.,Ph,acetonide etc.).In the third chapter,because of the problems existing in the oxidation method of C-aryl glycosides,we develop the synthesis method of glycoside carboxylic acid from C-vinyl glycosides.The differences in the oxidation activity in the reactions were compared experimentally and analyzed theoretically.Finally,the mechanism of the reaction was speculated.We anticipate this cyanide–free synthesis glycosyl carboxylic acids would find broad application in future.