Application Of S-glycosyl Isothiourea Salts In One-pot Synthesis Of S-glycoside Derivatives

Glycoside,in which a carbohydrate is covalently bound to another functional group via glycosidic bond,plays an important role in living organisms.With the coupling of carbohydrate to the parent compound,the solubility and biological activity could be dramatically improved.However,the O-glycosidic bond connecting the carbohydrate and aglycon is not stable to acidic conditions or to metabolic degradation.Alternatively,Sglycoside,an attractive substitutes for O-glycoside,has drawn wide attentions recently as it shows much better resistance to hydrolysis and biochemical degradation.Therefore,in this thesis,a one-pot synthesis method was developed to produce S-glycoside derivatives by the application of S-glycosyl isothiourea salts.Kojic acid,which is a product isolated from aerobic fermentative products of fungus,has been used as an anti-tyrosinase agent.Its derivatives have been applied in cosmetic products.However,kojic acid itself is sensitive to themal and easy to be oxidized.In this thesis,Sglycosyl isothiourea salts were synthesized in one-pot synthesis of S-glycoside modified kojic acid derivatives.The peracetylated glycosyl donor is used as a raw material to be converted into glucosyl iodide in iodine and triethylsilane system.After the reaction is completed,the product obtained does not need to be separated.The glucosyl iodide is further reacted with thiourea to prepare S-glycosyl isothiourea salts;Subsequent we explore and optimize reaction conditions of S-glycosyl isothiourea salts with 7-chloro-kojic acid under the reaction of a base for one-step synthesis of kojic acid derivatives,including glucose,mannose,Galactose,glucosamine,rhamnose,maltose,lactose,cellobiose.The advantage of this method is that the three-step reaction is completed in one pot,and only the last step is required for isolation and purification.The overall yield of the reaction is medium to good.In addition,using this method,a nucleophilic substitution reaction using an S-glycosyl isothiourea salt and a glucosyl iodide was also explored and optimized to stereoselectively synthesize thiotrehalose derivatives.Synthetic trehalose derivatives mainly include ?,?-1-thioglucose;?,?-1-thiomannose and ?,?-1-thiogalactose.