Scanning the potential energy surface of furanosyl oxocarbenium ions: models for reactive intermediates in glycosylation reactions.

A new scanning method with complementary graph to describe the ring potential energy surface of furanoses is introduced. Density functional theory at the B3LYP level of theory with the 6-311G(d,p) basis set is used to calculate the energy of the partially minimized structures. The method is used to determine the correlation between the preferred conformation of oxocarbenium ions that are model intermediates for a glycosylation reaction and recent experimental results. Key disagreements between the predicted geometry and the minima based on the scans described herein indicate that the preferred oxocarbenium ion conformation is not a consistent predictor of preferred stereochemistry of the products.