|TUD Organische Chemie||Immel||Publications||Poster||Abstract 07||View or Print (this frame only)|
Frieder W. Lichtenthaler, Hans J. Lindner, Stefan Immel, and Guido E. Schmitt
9th European Carbohydrate Symposium (EUROCARB XI), Utrecht, Netherlands, July 6-11, 1997, Abstract C5.
The structural characteristics of α-cycloaltrin (3), readily available from α-cyclodextrin (1) by a straightforward four-step protocol with 2,3-anhydro-α-cyclomannin (2) as the key intermediate, has been unraveled using X-ray techniques, 800 MHz spectra (D2O at 30 and 4°C) and molecular modeling (MD in water). In the solid-state, the altropyranoid rings adopt nearly perfect 4C1 and 1C4 chairs in an alternating sequence, entailing the macrocycle to be devoid of a through going cavity. From HTA calculations i.e. toward vacuum boundary conditions, the allskew (twistboat) 0S2 geometry emerges as the global energy minimum structure. In water, the altropyranoid rings in 3 adopt various conformations within the 1C4 3H2 0S2 range.
 Y. Nogami, K. Fujita, K. Ohta, K. Nasu, H. Shimada, C. Shinohara, and T. Koga, (J. Szejtli, L. Szente, Eds.), Proceedings of the 8th Internat. Symp. on Cyclodextrins, Kluwer Acad. Publ., Dordrecht, 1996, pp. 99-102.
Additional Graphics: Cycloaltrins