A SOLVATION-ASSISTED MODEL FOR ESTIMATING ANOMERIC REACTIVITY - PREDICTED VERSUS OBSERVED TRENDS IN HYDROLYSIS OF N-PENTENYL GLYCOSIDES

An attempt has been made to predict qualitative trends in reactivity a t the anomeric center, using N-bromosuccinimide-induced hydrolysis of n-pentenyl glycosides (NPGs) as the experimental model. Calculated rel ative activation energies based on internal energy differences between a reactant and the associated intermediate are not always in agreemen t with experimental observations. However, solvation energies obtained by the generalized Born surface area model in MacroModel developed by Still et al. give modified activation energies that are in excellent agreement with the experimentally observed trends. It is shown that th e solvation model does not disturb the normally observed reactivity tr ends that can be rationalized on the basis of internal energies alone. The value of the methodology has been demonstrated for several substr ates by first-calculating their relative activation energies, then tes ting them experimentally, and finding excellent agreement with predict ions.