title: Structure determination from conventional powder diffraction data: application to hydrates, hydrochloride salts, and metastable polymorphs.
abstract: Recent advances in crystallographic computing have made it possible to solve by powder diffraction methods structures that have not been possible to solve by single-crystal methods. Although there is vast improvement in the quality of data obtained from high-intensity synchrotron radiation, we found that surprisingly reliable results can be obtained from conventional laboratory sources. In this article we examine the application of Monte Carlo/simulated annealing methods for the determination of structures ranging in complexity from 9 to 15 degrees of freedom. We re-determine the structures of papaverine hydrochloride and erythromycin A dihydrate by the powder diffraction method and compare the structures to those determined by single-crystal diffraction methods. The structure of a metastable polymorphic form of acetohexamide, form B, is solved and examined spectroscopically. Its structure has not previously been solved by single-crystal techniques because of the small size of its crystals.
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, Indiana 46285, USA. gas@lilly.com
authors.forename: G A
authors.initials: GA
authors.lastname: Stephenson
mesh_terms: D000092:Acetohexamide / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D018360:Crystallography, X-Ray; D004917:Erythromycin / Q000737:chemistry; D007004:Hypoglycemic Agents / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009010:Monte Carlo Method; D010208:Papaverine / Q000737:chemistry; D010726:Phosphodiesterase Inhibitors / Q000737:chemistry; D011208:Powders / Q000737:chemistry*; D012996:Solutions; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D007004:Hypoglycemic Agents; D010726:Phosphodiesterase Inhibitors; D011208:Powders; D012996:Solutions; D004917:Erythromycin; D010208:Papaverine; D000092:Acetohexamide