Two stereoisomeric 3(I),2(II)-anhydro-alpha-cyclodextrins: a molecular dynamics and crystallographic study.
Regioselective epoxide ring opening of 2(I),3(I)-(2(I)S)-anhydro-alpha-cyclodextrin (1) through intramolecular attack of hydroxyl groups of neighboring glucose rings occurs in diequatorial fashion to yield 3(I),2(II)-anhydro-alpha-cyclodextrin (3) with a rigid glucopyranose-dioxane-glucopyranose tricyclic ring system, the usual diaxial opening and the gluco/altro-configured stereoisomer 2 cannot be detected. Molecular dynamic simulations in water were used to analyze the conformations of 1-3 and the stereochemical implications of this reaction. Due to the contracted 2,3-OH side of the torus, 3 features an inverted conicity compared to the parent alpha-cyclodextrin. A crystallographic study on the bis-3.3 n-PrOH nonahydrate not only displays little variations between the solid-state and solution geometries of 3, but also provides a molecular picture of a unique inclusion complex in which three n-propanol molecules are distributed in the cavity of a dimeric unit of 3 (monoclinic, space group P2(1), a=14.257(1), b=22.623(2), c=16.644(1) A, beta=104.82(1) degrees, all 19,278 reflections with I>2 sigma(I) yield R(F)=0.1017).
Immel
S
S
Institut für Organische Chemie, Technische Universität Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany. lemmi@sugar.oc.chemie.tu-darmstadt.de
Fujita
K
K
Fukudome
M
M
Bolte
M
M
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D003505:Cyclodextrins / Q000737:chemistry*; D004852:Epoxy Compounds; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D009038:Motion; D013237:Stereoisomerism; D013816:Thermodynamics
D003505:Cyclodextrins; D004852:Epoxy Compounds