2,5-Anhydrides of Sugars and Related Compounds

Publisher Summary This chapter discusses rationalization among the numerous methods for access to 2,5-anhydrides of aldoses. The chapter also singles out sugar derivatives in this class with regard to their properties and utilization. In context to methods of formation, there are several methods that constitutes the access to the 2,5-anhydroaldohexoses. These include deamination of aminoaldoses with nitrous acid, halogenolysis of halogenated derivatives, intramolecular displacement of sulfonates by the action of a base, and solvolysis of sulfonates. In specific, deamination of aminoaldohexoses with nitrous acid constitutes the oldest method for formation of 2,5-anhydroaldohexoses. It is noted that the results obtained by this method can be rationalized on a theoretical basis as a consequence of concomitant developments in certain other areas of organic chemistry. The action of nitrous acid on a primary, aliphatic amine is a complex process and leads ultimately to formation of carbonium ion, which is nonsolvated and chemically activated. The nature of the products, resulting from its decay is essentially determined by the conformation of the initial state.