Formation and Cleavage of the Oxygen Ring in Sugars

Abstract

This chapter discusses the formation and cleavage of the oxygen ring in sugars, and discusses some aspects of the interconversion of the cyclic forms of a carbohydrate to their acyclic forms and to each other. In general, the stability of the ring structure and the reactivity of a cyclic sugar are materially affected by the steric strain of its molecule. On the other hand, the formation of cyclic compounds from those acyclic carbohydrate derivatives having a number of competing hydroxyl groups is likewise of considerable interest. In the reversible reactions of this nature, an ultimate equilibrium is established that results in the predominant formation of the less strained, more stable ring-structures. In the irreversible reactions, such as the deamination of acyclic amino sugars with nitrous acid, the resulting cyclic products usually contain the strained, nearly planar, five-membered ring-structure.