1,6-Anhydro Derivatives of Aldohexoses

The 1,6-anhydroaldohexopyranoses and 1,6-anhydroaldohexofuranoses are aldohexose derivatives that can be formed from free hexoses by dehydration in such a way that intramolecular glycosides containing a glycosidically linked, primary hydroxyl group are formed. Depending on whether the D-hexose adopts the pyranoid or furanoid form, two analogous, bicyclic systems are formed—namely, 1,6-anhydro-β-D-aldohexopyranoses having a 6,8-dioxabicyclo[3.2.l]octane skeleton from the former, and 1,6-anhydro- β-D-aldohexofuranose having a 2,8-dioxabicyclo[3.2. l]octane skeleton from the latter. In their chemical properties, both these types of compound resemble to a certain degree the methyl β-D-aldopyranosides or the methyl α- or β-D-aldofuranosides. They do not have reducing properties, and are relatively stable in alkaline media, but are hydrolyzed by acids to the free hexoses. A characteristic feature of these compounds is their steric rigidity in the crystalline state as well as in solution. 1,6-anhydro-β-D-hexopyranoses are widely used in the synthesis of hexoses and their derivatives, oligosaccharides, and for polymerization to polysaccharides.