Structural study of monosubstituted β-cyclodextrins. Crystal structures of phenylthio-β-cyclodextrin and phenylsulphinyl-β-cyclodextrin and spectroscopic study of related compounds in aqueous solution

Abstract

The crystal structures of two monosubstituted β-cyclodextrins which have bulky hydrophobic groups instead of primary hydroxy groups were determined by X-ray diffraction. These compounds consist of the host (cyclodextrin moieties) and guest parts (hydrophobic groups), and have the ability to act as both host and guest at the same time. The crystal structures were solved by using Patterson maps, rotation functions, and trial-and-error methods combined with a rigid-body least-squares technique. The structures were refined by using a block-diagonal least-squares method to R values of 0.14 and 0.13. Hydrophobic groups are intermolecularly included in the cyclodextrin cavity of another molecule, and novel helical polymers are formed by repetition of this intermolecular inclusion. A spectroscopic study confirmed that this intermolecular inclusion occurs in aqueous solution.