Crystal structures of heptakis(2,6-di-O-ethyl)cyclomaltoheptaose.
Heptakis(2,6-di-O-ethyl)-beta-cyclodextrin (DE-beta-CD) was crystallized in two forms from hexane and 95% aqueous methanol, respectively: A form I crystal with the space group P2(1)2(1)2(1) and a form II crystal with the space group P3(1). In both crystals, DE-beta-CD molecules are in a round shape with intramolecular O-3-H...O-2 hydrogen bonds. In the form I crystal, the DE-beta-CD molecules are arranged along the twofold screw axis to form a helically extended polymeric chain by including the 6-O-ethyl groups of the adjacent molecule. One hexane molecule with twofold disorder is located in the intermolecular channel along the a-axis. In contrast, the DE-beta-CD molecules in the form II crystal form a helical arrangement along the threefold screw axis. One methanol and one water molecule are included on the O-6 side of the molecular cavity. The water molecule links the methanol molecule and two ethoxy groups of the adjacent DE-beta-CD molecule with hydrogen bonds. The result suggests the important role of solvent in the formation of helical arrangement of DE-beta-CD molecules.
Harata
K
K
National Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, Tsukuba, Ibaraki, Japan. harata@nibh.go.jp
Hirayama
H
H
Uekama
K
K
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D003505:Cyclodextrins / Q000737:chemistry* / Q000302:isolation & purification; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012997:Solvents; D047392:beta-Cyclodextrins
D003505:Cyclodextrins; D012997:Solvents; D047392:beta-Cyclodextrins; C055959:heptakis(2,6-diethyl)beta-cyclodextrin