Complexes of Methylated CyDs

Hexakis(2,6-di-0-methyl)-a-CyD complexes with a small guest molecule, such as iodine and 1-propanol, crystallize with the cage-type packing structure [185]. Compared with the structure of the corresponding -CyD complex, the guest molecules in the both complexes are shifted to the secondary hydroxyl side from the center of the cavity. 3-Iodopropionic acid [186], m-nitroaniline [187], and acetonitrile [188] are also fully accommodated in the host cage . A 3-0 acetylated host, hexakis(2,6-di-0-methyl-3-0-acetyl)-a-CyD, was crystallized from butylacetate [189]. In spite of the disruption of intramolecular hydrogen bonds, the host molecule is in a round shape because of the inclusion of butylacetate. 

Heptakis(2,6-di-0-methyl)-j8-CyD includes acetic acid [194], 2-adamantanol [190], n-butylacrylate [191], and isobomylacrylate [191] in its cavity. The complex with carmofur, which is larger than the host cavity, crystallizes in the layer-type packing structure [156]. Compared with the crystal structures of other methylated CyD 

Permethylation of hydroxyl groups makes the 06 side narrower because of the sharp inclination of 2,3,6-tri-O-methylglucose units caused by the steric hindrance between methyl groups bonded to 03 and 02 of adjacent 2,3,6-tri-O-methylglucose unit. As the result, m-nitroaniline [187] and p-nitrophenol [197] are included with their hydroxyl or amino group located at the 06 side, that is, in the orientation upside down compared with the corresponding complex with the parent a-CyD (Fig. 

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