Direct aqueous synthesis of cyanomethyl thioglycosides from reducing sugars; ready access to reagents for protein glycosylation

Unprotected carbohydrates can be directly converted into cyanomethyl thioglycosides in a completely stereoselective manner by reaction with 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and mercaptoacetonitrile in aqueous solution in the presence of triethylamine. Reaction with methoxide provides 2-imino-2-methoxyethyl (IME) thioglycosides, which may be used directly for the glycosylation of surface protein lysine residues. Unprotected carbohydrates can be directly converted into cyanooethyl thioglycosides, which in turn may be used for protein glycosylation, in a completely stereoselective manner by reaction with 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and mercaptoacetonitrile in aqueous solution.