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Two stereoisomeric 3(I),2(II)-anhydro-alpha-cyclodextrins: a molecular dynamics and crystallographic study
S Immel1, K Fujita, M Fukudome
1Institut für Organische Chemie, Technische Universität Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany. lemmi@sugar.oc.chemie.tu-darmstadt.de
Carbohydrate Research
|December 1, 2001
Summary
Regioselective epoxide ring opening of anhydro-alpha-cyclodextrin yields a unique tricyclic system. Molecular dynamics and crystallography reveal its inverted conicity and inclusion complex formation.
Area of Science:
- Carbohydrate Chemistry
- Supramolecular Chemistry
- Structural Chemistry
Background:
- Anhydro-alpha-cyclodextrins are cyclic oligosaccharides with potential applications in host-guest chemistry.
- Understanding their reactivity and structural properties is crucial for designing novel functional materials.
Purpose of the Study:
- To investigate the regioselectivity and stereochemical outcome of epoxide ring opening in 2(I),3(I)-(2(I)S)-anhydro-alpha-cyclodextrin (1).
- To analyze the conformational properties and stereochemical implications using molecular dynamics simulations.
- To elucidate the solid-state structure and inclusion complex formation of the resulting anhydro-alpha-cyclodextrin (3) through X-ray crystallography.
Main Methods:
- Regioselective epoxide ring opening reaction.
- Molecular dynamic simulations in aqueous solution.
- X-ray crystallography of a novel inclusion complex.
Main Results:
- The reaction exclusively yields 3(I),2(II)-anhydro-alpha-cyclodextrin (3) via diequatorial epoxide opening, forming a rigid tricyclic system.
- Molecular dynamics simulations confirm the observed stereochemistry and reveal the conformational impact of the tricyclic structure, including an inverted conicity.
- Crystallographic analysis of the bis-3.3 n-PrOH nonahydrate shows minimal deviation between solid-state and solution structures and details a unique inclusion complex with a dimeric unit of 3 encapsulating n-propanol molecules.
Conclusions:
- The intramolecular epoxide ring opening of anhydro-alpha-cyclodextrin proceeds with high regioselectivity and stereospecificity.
- The resulting tricyclic structure (3) exhibits distinct conformational features, including inverted conicity, compared to parent cyclodextrins.
- The crystallographic study provides valuable insights into the solid-state behavior and host-guest properties of this modified cyclodextrin.
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