Conformational studies on cycloamyloses

Abstract

The "non-bonded" interaction energies have been computed for cyclohexaamylose, cycloheptaamylose, cyclooctaamylose. From hydrogen-bond criteria the conformation having an angle of 119° at the bridge oxygen atom is preferred for cyclohexaamylose. It is also shown that cycloamyloses having fewer than six ^D -glucose residues could not be cyclized because of steric overlaps. Out of three possible cyclic compounds, cyclohexaamylose has the lowest energy. Cyclohexa-, -hepta-, and -octa-amyloses are stabilized by the formation of intramolecular hydrogen bonds between contiguous ^D -glucose residues. These intramolecular hydrogen bonds are stronger in the hepta- and octa-amyloses than in the hexaamylose.