Hydrolysis of α- and β-Glycosides. New Experimental Data and Modeling of Reaction Pathways

The cyclization of oxocarbenium ion conformers 6α and 6β (from 11E and 11Z) gave only the β-glycoside 1 β, and the addition of methanol to the oxocarbenium ion 3 yielded mainly the α-glycoside 1 α with both experiments being carried out under kinetically controlled conditions. RHF/6.31G* calculations reproduce well these experimental results and show that the endocyclic and the exocyclic C−O bond cleavage processes can compete in the hydrolysis of 1 β, whereas 1 α gets hydrolyzed by exocyclic C−O bond cleavage only.