Chapter 2 - Anomeric Effect in Saturated Heterocyclic Ring Systems

Abstract

Abstract The anomeric effect is one of the most important factors influencing conformational behavior and also the reactivity of saturated heterocyclic systems. The present review describes some salient observations in saturated heterocyclic compounds reported in the 1992 – 2011 period. The generally accepted rationalizations based on (1) dipole-dipole interactions destabilizing the equatorial conformer, and (2) an stereoelectronic interaction which stabilizes the axial orientation of the anomeric substituent are reviewed. In particular, the accumulated experimental (e. g., structural changes, spectroscopic behavior, and relative reactivity) and theoretical observations suggesting that both factors contribute to the anomeric effect is presented. Nevertheless, alternative theories that have been advanced recently to account for the origin of the anomeric effect are summarized. The present review will make evident that further investigation of this effect, with the use of new model compounds and application of novel and insightful experimental and computational strategies is required for the understanding of the fundamental nature of the anomeric effect. Furthermore, it is clear that proper application of the anomeric effect in synthetic strategies may lead to highly valuable stereoselective reactions.