Crystal structure herring-bone arrangement

Harata et al. [23] reported that the crystal structure of 2-0-[(S)-2-hydroxy-propyl]-y0-CD was solved by X-ray diffraction (Fig. 5). The molecules are arranged in a herring-bone fashion to form a cage-type packing structure. The hydroxypropyl group is inserted into the cavity of an adjacent molecule related by a two-fold screw axis. 

In the cage type crystal structures, the a-cyclodextrin molecules are arranged such that the apertures are blocked on both ends by contiguous molecules. Two different forms of cage structures occur, one with a herring-bone-like, crosswise displacement of the a-cyclodextrin molecules, the other with the a-cyclodextrin molecules opposite, face to face to each other and displaced such that one molecule overlaps the neighbour below and therefore closes up its aperture. Figures 5a, b. 

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