title: Conformational polymorphism in bicalutamide.
abstract: Two crystalline forms (forms I and II) and an amorphous phase of bicalutamide were fully characterized through combined results of differential scanning calorimetry, X-ray powder and single crystal diffraction and Raman spectroscopy. Each polymorph crystallizes with one molecule in the asymmetric unit and the molecular conformations are quite different between them. The main difference is provided by C12-C11-S8-C5 torsion angle, which assumes a value of -88.3(4) degrees (-Syn-Clinal) and 72.5(4) degrees (+Syn-Clinal) in forms I and II, respectively. Consequently, molecules in form I show an open folding and molecules in form II a closed one. The relative stability between forms I and II is presented in an energy versus temperature diagram, where forms I and II are considered as a monotropic system, being form I the more stable one. The amorphous phase was observed very metastable and it converts to form II spontaneously at RT in around a week.
authors.affiliation: Unidad de Actividad Física, Comisión Nacional de Energía Atómica, Avenida Gral. Paz 1499, 1650 San Martín, Buenos Aires, Argentina. vega@cnea.gov.ar
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Vega
authors.forename: Griselda
authors.initials: G
authors.lastname: Polla
authors.forename: Andrea
authors.initials: A
authors.lastname: Martinez
authors.forename: Elsa
authors.initials: E
authors.lastname: Mendioroz
authors.forename: María
authors.initials: M
authors.lastname: Reinoso
mesh_terms: D000726:Androgen Antagonists / Q000737:chemistry*; D000813:Anilides / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D004355:Drug Stability; D008968:Molecular Conformation; D009570:Nitriles; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman; D014105:Tosyl Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000726:Androgen Antagonists; D000813:Anilides; D000970:Antineoplastic Agents; D009570:Nitriles; D014105:Tosyl Compounds; C053541:bicalutamide