29] - Chlorodeoxy Sugars via (Chloromethylene)-dimethyliminium Chloride Reactions: 6-Chloro-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-pyranose and 6-Chloro-6-deoxy-1,2:3,5-di-O-isopropylidene-α-D-glucofuranose

Abstract

Chloromethylene dimethyliminium chloride is a strong electrophilic amide halide that reacts with the alcoholic groups of sugar derivatives to give formate ester through iminoester salts. When solutions of such salts are heated, chlorodeoxy sugars are formed, especially in the case of carbohydrate derivatives containing isolated hydroxyl groups as a result of nucleophilic attack of chloride ion on the carbon atom(s) bearing the iminoester group. The replacement of a secondary hydroxyl group in derivatives containing cyclic ketals, however, may be accompanied by rearrangement to give chlorodeoxy sugar derivatives, which are different from those expected on the basis of direct replacement of the hydroxyl group. Chloromethylene dimethyliminium chloride also reacts with anhydrosugar derivatives to give products containing one or two chlorine atoms, depending on the nature of the substituents present in the molecule.