Conformational Differences Between O- and C-Glycosides: Theα-O-Man-(1→1)-β-Gal/α-C-Man-(1→1)-β-Gal Case- A Decisive Demonstration of the Importance of theexo-Anomeric Effect on the Conformation of Glycosides

Abstract

The conformational behavior of alpha-O-Man-(1-->1)-beta-Gal (1) and its C-analogue (2) has been studied using J/NOE NMR data, molecular mechanics, molecular dynamics, and ab initio calculations. The population distribution around the glycosidic linkages of 1 and 2 is rather different, especially for the alpha-Man linkage. A lower limit for the exo-anomeric effect in water has been experimentally determined.