Redetermination of bis{(1S,2S,4S,5R)-2-[(R)-hydroxy(6-methoxy-4-quinolyl)methyl]-5-vinylquinuclidinium} sulfate dihydrate

The structure of the title compound, known as quinine sulfate dihydrate, 2C(20)H(25)N(2)O(2)+center dot SO(4)(2-)center dot 2H(2)O, was previously reported by Mendel [Proc. K. Ned. Akad. Wet. (1955), 58, 132-134], but only the [010] projection was determined. Hence, we have redetermined its crystal structure at 100 K using three-dimensional data. The asymmetric unit consists of a quininium cation, viz. (R)-(6-methoxyquinolinium-4-yl)-[( 1S,2S,4S,5R)-5-vinylquinuclidinium-2-yl]methanol, one half of a sulfate anion and a water molecule. The S atom occupies a special position on a twofold axis. The packing is characterized by infinite columns, consisting of sulfate anions and water molecules, linked through hydrogen bonds along the b axis, and further stabilized by hydrogen bonds to quininium cations. The quininium cations interact further through C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions.