Regioselective alkylation and acylation of carbohydrates engaged in metal complexes

Substituted carbohydrate derivatives (D-gluco, D-manno, and D-galacto) having two free hydroxyl groups were converted into their metal chelates by reaction with sodium hydride and a metal chloride (cupric or mercuric) in either oxolane or 1,2-dimethoxyethane. Reaction of these metal chelates with allyl, benzyl, or methyl iodide, or acetic anhydride or benzoyl chloride, gave a mixture of di-, mono-, and un-substituted products in which one monosubstituted derivative preponderated. In the alkylation of copper chelates, disubstitution was absent. Appropriate choice of metal ion and organic reagent often permits selective substitution on either of two hydroxyl groups. Products were separated by liquid chromatography, and characterized by 1H- and 13C-n.m.r. spectroscopy.