THE BROMINOLYSIS OF CARBOHYDRATE IODIDES: I. ACETYLATED 6-DEOXY-6-IODO AND 2-DEOXY-2-IODO GLYCOSIDES

Abstract

Reaction of methyl 6-deoxy-6-iodo-α-D-glucopyranoside triacetate with an excess of bromine in glacial acetic acid; N in potassium acetate, gave a 1.1:1 mixture of the products resulting from replacement of the iodine by bromine and by acetoxy group, respectively. When 2 moles of silver acetate were present per mole of bromine, the reaction was much more rapid and only methyl α-D-glucopyranoside tetraacetate was formed. The brominolysis of methyl 2-deoxy-2-iodo-α-D-mannopyranoside triacetate proceeded at a useful rate only when catalyzed by silver acetate. The main product of the reaction appeared to be methyl 3-acetoxy-2-bromo-2-deoxy-α-D-arabino-hexopyranoside triacetate. The compound could be converted by way of sodium borohydride reduction to methyl 2-bromo-2-deoxy-α-D-altropyranoside and by way of zinc dust reduction to methyl 2-deoxy-α-D-erythro-hexopyranoside-3-ulose diacetate. About 20% of the reaction proceeded with migration of the methoxy group to the 2-position to yield 2-O-methyl-D-glucose tetraacetate. The mechanisms of these reactions are discussed.