Iodonium-Promoted Glycosidation With Glycosyl Ynenoates As Donors

Carbohydrate compounds mediate a variety of biological processes,and have complex and diverse biological significance and potential medicinal values.Chemical synthesis is currently the main approach to obtain structure-determined and pure carbohydrate compounds.However,the development of efficient and convenient methods of glycosylation has always been one of the long-standing challenges in the development of glycochemistry.The method of iodonium as an activator of glycoside donors has been applied to the glycosylation with a variety of glycoside donors including glucosinolates,but there is no report on the method of applying iodonium as an activator to glycosylation with glycosyl ynenoates as donors.NIS/TfOH and NIS/TMSOTf are cheap and easily available activators.The research on the activators’ efficiency of glycosylation with glycosyl ynenoates as donors to form O-glycosides remains to be done.Here,we report a versatile iodonium-promoted glycosidation with glycosyl ynenoates as donors for the highly efficient synthesis of O-glycosides.The glycosidation highlights the merits of mild reaction conditions,cheap activators,extremely wide substrate scope,and good to excellent yields.Based on this method,we successfully synthesized the disaccharide analogue containing the Gal-GalNAc fragment with NIS/TfOH or NIS/TMSOTf as activators.Then,a deprotecction attempt is made to obtain an all-hydroxy-naked target disaccharide that can be used for biological activity testing.