INVOLVEMENT OF N-SIGMA(ASTERISK) INTERACTIONS IN GLYCOSIDE CLEAVAGE

Proton-induced cleavage of acetals and glycosides has been investigated by ab initio methods. Bond lengths and bond angles are described as a function of conformation for protonated and unprotonated versions of dimethoxymethane. The path of the cleavage reaction is described in terms of conformation as well as hybridization of the donor oxygen. Lone pair orbitals on the donor oxygen are considered with respect to cleavage. The results are then projected onto pyranosides using our H-4(3) (axial anomer) and (4)E (equatorial anomer) transition state models for glycoside hydrolysis.