Selective transformations of the anomeric centre in water using DMC and derivatives

Abstract

2-Chloro-1,3-dimethylimidazolinium chloride (DMC) and its derivatives are useful for numerous synthetic transformations, which involve selective activation of the anomeric centre of unprotected reducing sugars in water. This chapter summarises research reported to date using DMC and derivatives, such as 2-azido-1,3-dimethylimidazolinium hexafluorophosphate (ADMP). DMC has been successfully employed for the synthesis of glycosyl oxazolines, 1,6-anhydro-, 1-azido-, and a variety of thioglycosides. The use of ADMP allows the one-pot synthesis of glycosyl triazoles in water via the Cu-catalysed azide-alkyne Huisgen cycloaddition reaction. This latter methodology can be applied to a wide variety of carbohydrates and is also amenable to convergent glycopeptide synthesis in which oligosaccharides are directly conjugated to peptides that contain propargyl glycine residues. Such protecting group free methodologies, particularly when applied to complex oligosaccharides isolated from natural sources, may allow ready access to a wide variety of biologically interesting glycoconjugates.