Crystal structure of anhydrous heptakis-(2,6-di-O-methyl) cyclomaltoheptaose (dimethyl-β-cyclodextrin)

An X-ray diffraction study was carried out on dimethyl-β-cyclodextrin which crystallized from aqueous solution at 60°C without water of hydration. The molecule adopts a round shape which is stabilized by systematic intramolecular O-3H ż O-2 hydrogen bonds between neighboring glucose units. The O-6C-8 groups of three glucoses are oriented towards the molecular axis so that the cyclodextrin cavity is closed at one end. The remaining volume of the bowl-shaped cavity is occupied by part of the C-6O-6C-8 rim of a neighboring molecule (self-inclusion).