Crystal structure of 6-O-[(R)-2-hydroxypropyl]cyclomaltoheptaose and 6-O-[(S)-2-hydroxypropyl]cyclomaltoheptaose.

Crystal structures of 6-O-[(R)-2-hydroxypropyl]- and 6-O-[(S)-2-hydroxypropyl]-cyclomaltoheptaose were determined by X-ray analysis. In both structures, the 2-hydroxypropyl group is inserted into the macrocyclic cavity of the next molecule related by the two-fold screw axis, and a helically extended polymeric structure is formed by repetition of the intermolecular inclusion. The hydroxyl group of the substituent group penetrates through the macrocyclic ring from the secondary hydroxyl side and is linked to an HO-6 group by a hydrogen bond. Comparison of intermolecular contacts of the substituent group indicates that the (S)-2-hydroxypropyl group is better fitted to the cavity than the (R)-2-hydroxy-propyl group.