|TUD Organische Chemie||Immel||Publications||Lectures||Abstract 03||View or Print (this frame only)|
Stefan Immel, Guido Schmitt, and Frieder W. Lichtenthaler
9thInternational Symposium on Cyclodextrins, Santiago de Compostela, Spain, May 31-June 3, 1998, Abstract 2-O-5.
α-Cycloaltrin, readily available from -cyclodextrin via a straightforward four-step protocol, adopts in the solid-state a C3 symmetrical conformation with nearly perfect 4C1 and 1C4 chairs in an alternating sequence, but lacks a "through-going" cavity.
1H and 13C NMR experiments of α-cycloaltrin show a complex conformational equilibrium 4C1 OS2 1C4 for each of the altrose units.
Molecular dynamics (MD) simulations and temperature-dependent 800 MHz 1H and 13C NMR spectra (D2O at 30 and 4°C) point toward a fast dynamic equilibrium with preferred altrose conformations in the 1C4 OS2 range. Low-temperature broadening of the C-4 and C-5 NMR signals indicate multiple conformations of α-CA in solution which are likely to ellaborate central cavities similar to those formed by cyclodextrins.
Y. Nogami, K. Fujita, K. Ohta, K. Nasu, H. Shimada, C. Shinohara, and T. Koga, J. Inclusion Phenom. Mol. Recognit. Chem. 1996, 25, 57-60.
Y. Nogami, K. Nasu, T. Koga, K. Ohta, K. Fujita, S. Immel, H. J. Lindner, G. E. Schmitt, and F. W. Lichtenthaler, Angew. Chem. 1997, 109, 1987-1991; Angew. Chem. Int. Ed. Engl. 1997, 35, 1899-1902.
Additional Graphics: Cycloaltrins