Metergoline II: structure solution from powder diffraction data with preferred orientation and from microcrystal
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Metergoline is a dopamine agonist and serotonin antagonist used both in human and veterinary medicine. In addition to the previously known crystalline form, a new polymorph, which crystallizes from aqueous solution, was found. Since it was initially impossible to prepare a single crystal of quality suitable for single crystal X-ray diffraction measurements using a conventional laboratory source, the structure was solved from the powder diffraction data using synchrotron radiation. The structure determination also included solving the effects of preferred orientation. Characterization was simultaneously done by solid-state NMR spectroscopy. Finally, a small single crystal suitable for synchrotron diffraction was found after numerous tries. Crystal structure determination using this single crystal confirmed the powder-based solution. Comparison of information obtained by different experimental methods (powder diffraction, ssNMR, single crystal diffraction) was made.
KeywordsCrystal structure Metergoline Powder diffraction Preferred orientation
This study was supported by the grant of the Czech Grant Agency (GAČR 203/07/0040), grant from the Grant Agency of the Academy of Sciences of the Czech Republic (IAA400500602) and by the research program MSM6046137302 of the Ministry of Education, Youth and Sports of the Czech Republic. We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and we would like to thank Denis Testemale for assistance in using beam line BM01B.
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