Theoretical studies on hydrogen bonding, NMR chemical shifts and electron density topography in alpha, beta and gamma-cyclodextrin conformers

Hydrogen-bonded interactions in alpha-, beta-, and gamma-CD conformers are investigated from the molecular electron density topography and chemical shift in the nuclear magnetic resonance (NMR) spectra calculated by using the Gauge Invariant Atomic Orbital (GIAO) method within the framework of density functional theory. For the lowest-energy CD conformers in the gas phase, the O3-H...O2' hydrogen-bonding interactions are present. Calculated 1H NMR chemical shifts (delta H) correlate well with the hydrogen-bond distance as well as electron density at the bond critical point in the molecular electron density (MED) topography. The conformers of beta- and gamma-CD comprised of relatively strong secondary hydroxyl interactions are stabilized by solvation from polar solvents.