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Cyclofructins: Geometries, Electrostatic and Lipophilicity Patterns, and Inclusion Complexes

Stefan Immel, Guido Schmitt, and Frieder W. Lichtenthaler

XVIIIth International Carbohydrate Symposium, Milano, Italy, July 21-26, 1996, Abstract AO027.

Cyclofructins composed of six (α-CF, 1) to ten (5) β(1→2)-linked fructofuranose units (i.e. cyclo[D-Frufβ(1→2)]n with n = 6 - 10) were subjected to conformational analysis using "Monte-Carlo" simulations based on the PIMM91[1] force field[2,3]. Far-reaching similarities and identical over-all conformations of the solid-state geometry[4] of -cyclofructin (1) and its computer-generated form provide information about the reliability of the computational analysis.

1 cyclo[D-Frufβ(1→2)]6
2 cyclo[D-Frufβ(1→2)]7
3 cyclo[D-Frufβ(1→2)]8
4 cyclo[D-Frufβ(1→2)]9
5 cyclo[D-Frufβ(1→2)]10

Calculation of the molecular surfaces for the energy-minimum structures establishes a disk-type shape of the cyclofructins with six to eight residues, ring enlargement to nine and ten residues leads to torus-shaped molecules with central cavities that conceivably allow for the formation of inclusion complexes. The color-coded projection of molecular lipophilicity patterns (MLPs)[5] and electrostatic potential profiles (MEPs) onto these surfaces displays the crown ether-like properties of the disk-shaped cyclofructins. The central cavities of 4 and 5 should be amenable to the formation of inclusion complexes similar to those formed by cyclodextrins.

CF6 molecular surface
CF7 molecular surface
CF8 molecular surface
CF9 molecular surface
CF10 molecular surface
CF6 cross-section cut
CF7 cross-section cut
CF8 cross-section cut
CF9 cross-section cut
CF10 cross-section cut

Fig. 1. Geometries with the dotted contact surfaces and cross section plots of the global energy-minimum structures (PIMM91) of the cyclofructins 1 - 5 composed of six to ten (1→2)-linked fructose units.

[1] A. E. Smith, H. J. Lindner,J. Comput.-Aided Mol. Des. 1991, 5, 235-262.
[2] S. Immel, F. W. Lichtenthaler, Liebigs Ann. Chem. 1996, 39-44.
[3] S. Immel, F. W. Lichtenthaler, to be submitted.
[4] M. Sawada, T. Tanaka, Y. Takai, T. Hanafusa, T. Taniguchi, M. Kawamura, T. Uchiyama, Carbohydr. Res. 1991, 217, 7-17.
[5] M. Waldherr-Teschner, T. Goetze, W. Heiden, M. Knoblauch, H. Vollhardt, J. Brickmann, in: Advances in Scientific Visualization (Eds.: F. H. Post, A. J. S. Hin), Springer Verlag, Heidelberg, 1992, pp. 58-67.

Additional Graphics: Cyclofructins

© Copyright PD Dr. S. Immel