Syntheses of 3-deoxy-3-substituted-D-glucose derivatives. Part I. Improvements in preparation of and nucleophilic additions to 1,6:2,3-dianhydro-4-Obenzyl-β-D-allopyranose

Abstract

The yield of the five-step preparation of 1 ,6:2,3-dianhydro-4-O-benzyl-β-D-allopyranose from 1,6-anhydro-β-D-glucopyranose has been raised to 33% from 12% by modifying conditions or methods for four of the steps. It has been demonstrated that nucleophilic addition to the former compound provides a general route to 1,6-anhydro-3-deoxy-3-substituted-m-glucopyranose derivatives, although reactions with large nucleophiles proceed either slowly or not at all. A number of nucleophiles, including chloride, fluoride, cyanide, alkylsulfide, and dimethylamine, gave this type of product in good yield (73-87%). The conditions used to introduce a chloro group, a catalytic amount of tetraethylammonium chloride in 1,1,2,2-tetrachloroethane at reflux, had not previously been used for carbohydrate epoxides. The methyl substituted product was obtained in highest yield with dimethyl magnesium. By-products from this reaction included the products of a Witting rearrangement and of an elimination. All addition products were present in the 1C4 conformation.