Prediction of Anti and gauche vicinal proton‐proton coupling constants for hexapyranose rings using a generalized karplus equation

A new coupling constant ‐ torsion angle relation for the three‐bond 1H‐1H spin‐spin coupling constants is utilized to explore the effect of endocyclic and exocyclic oxygen atoms on Jae, Jee and Jaa in hexapyranoid systems. Attention is paid to common stereochemical surroundings rather than to individual compounds. It is shown that a simplified model for the flattened six‐membered ring, incorporating a constant geometry irrespective of the location of the coupled protons, correctly reproduces all the main trends observed.