Hydrolysis of alpha-and beta-Glycosides.New Experimental Data and Modeling of Reaction Pathways

摘要

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