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Molecular Modeling of Saccharides, Part XI.

Towards Understanding Formation and Stability of Cyclodextrin Inclusion Complexes: The Lipophilicity Patterns of some Typical Examples

Frieder W. Lichtenthaler and Stefan Immel

Starch/Stärke 1996, 48, 145-154.

Five cyclodextrin inclusion complexes typical examples for their solid-state as well as exemplary "frozen molecular images" of their status in solution were subjected to a molecular modeling study comprising the computer-assisted generation of the lipophilicity patterns, i.e. the p-iodoaniline inclusion into α-CD, the complexes of β-CD with 1,4-butanediol, adamantane-1-carboxylic acid, and adamantane-1-methanol, and the unique 12-crown-4 ether inclusion compound of γ-CD. Based on their solid-state structures, the "solvent-accessible" contact surfaces were generated by the MOLCAD program. Calculation and color-coded projection of the molecular lipophilicity patterns (MLP's) onto these surfaces easily allows to locate the hydrophobic and hydrophilic surface regions of the guest molecules and CD-hosts alike. Their detailed analysis revealed a far-reaching, mostly complete complementarity between the hydrophobic surface areas of the guest and the hydrophobic domains within the CD cavity. This striking tendency to optimize the reciprocal concurrence of lipophilic as well as hydrophilic domains at the guest-host-interface may accordingly be an important, if not the decisive element in orienting the guest into the cavity and in determining the stability of the complex, particularly in cases where the guest is devoid of polar groups. If these are present, dipole-dipole alignments and the need for their solvation may diminish the importance of hydrophobic attractions for orienting and stabilizing the guest within the CD cavity.

Additional Graphics: Cyclodextrin Inclusion Complexes

© Copyright PD Dr. S. Immel