Carbohydrates chloroacetic acid

In the fourth approach, the carbohydrate can be reversibly converted into a glycosylamine by treatment with an ammonium salt (263,264) or an aliphatic amine (265,266). However, these derivatives are quite unstable in slightly acidic medium or neutral medium. They are further stabilized by acylation with, for example, anhydride acetic (265), p-vinylbenzoyl chloride (267), acryloyl chloride (263), or chloroacetic anhydride, followed by ammonolysis (268) (Fig. 36). The N-linked structure of these glycosynthons is distinct from the open chain structure of the carbohydrate derivatives described above. This method may be useful to introduce complex oligosaccharides. 

Besides acetates and benzoates many other types of carboxylic acid esters can be formed, such as chloroacetates, trifluoroacetates, pivalates, carbonates, and thiocarbonates, by reaction with chloroacetic anhydride, trifluoroacetic anhydride, pivaloyl chloride (2,2-dimethyl propanoyl chloride), phosgene or methylchloro-formate, and carbon disulfide or carbonyl sulfide, respectively. Each of the ester derivatives imparts specific chemical properties to the carbohydrates so they can be used selectively in synthetic schemes. It was found that the sulfonic acid esters... 

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