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

2-O-[(S)-2-Hydroxypropyl]cyclomaltoheptaose crystallises in the monoclinic space group P2(1) with unit-cell dimensions a = 15.072(1), b = 10.409(1), c = 20.623(2) A, and beta = 108.52(1) degrees. The structure was solved by X-ray diffraction and refined to an R-value of 0.096. The macrocyclic ring of the cyclomaltoheptaose moiety is less symmetrical than that in cyclomaltoheptaose. The glucose residue that carries the hydroxypropyl group inclines much more with its primary hydroxyl side towards the inside of the macrocycle than the other glucose residues. 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, and the hydroxyl group is linked to an HO-6 via OH...water...OH hydrogen bonds. The crystal contains 8.5 water molecules which occupy 11 sites. Two water molecules are included at the primary hydroxyl side of the cyclomaltoheptaose cavity.