title: Polymorphic forms of cilostazol.
abstract: Two unique conformational polymorphic forms of the compound 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydroquinolin-2(1H)-one (cilostazol), C(20)H(27)N(5)O(2), have been discovered and characterized using single-crystal X-ray structural analysis. A third polymorph also exists, but acceptable crystals could not be obtained. Features of both reported polymorphic structures include a chair conformation of the cyclohexyl ring and puckering in the quinolinone ring. The major feature distinguishing the two polymorphic forms is a rotational twisting of the butoxy chain between the tetrazole and quinolinone rings. This difference in conformation influences the intermolecular forces, and hence the packing of the two molecules during crystallization.
authors.affiliation: aaiPharma, 2320 Scientific Park Drive, Wilmington, North Carolina 28405, USA.
authors.forename: Linda B
authors.initials: LB
authors.lastname: Whittall
authors.forename: Robert R
authors.initials: RR
authors.lastname: Whittle
authors.forename: Grayson W
authors.initials: GW
authors.lastname: Stowell
mesh_terms: D000077407:Cilostazol; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry*; D013777:Tetrazoles / Q000737:chemistry*
chemical_list: D010975:Platelet Aggregation Inhibitors; D013777:Tetrazoles; D000077407:Cilostazol