addenda and errata
Capecitabine from X-ray powder synchrotron data. Corrigendum
aDepartment of Solid State Chemistry, ICT Prague, Technicka 5, Prague, Czech Republic, bIVAX Pharmaceuticals s.r.o., R&D, Opava, Czech Republic, cPharmaceuticals Research and Development, Branisovska 31, Ceske Budejovice, Czech Republic, and dID31 Beamline, ESRF, 6 rue Jules Horowitz, BP 220, F-38043 Grenoble Cedex, France
*Correspondence e-mail: rohlicej@vscht.cz
In the paper by Rohlicek et al. [Acta Cryst. (2009), E65, o1325–o1326], one H atom was placed incorrectly.
Following our powder-diffraction study of capecitabine (Rohlicek et al., 2009), Malińska et al. (2014) published the of the same molecule based on single-crystal data. Although they modelled the wrong enantiomer [as was pointed out by Kratochvil et al. (2016)], the structures are very similar after inverting the single-crystal structure, including the disordered part of the molecule (Fig. 1). Since single-crystal diffraction is more sensitive to H atoms than powder diffraction, Malinska et al. (2014) were able to locate the H atoms directly. This indicated a different tautomeric form of capecitabine to that assumed in our study, and as they pointed out, we had therefore placed one H atom wrongly.
In our defence, in the powder study, we placed the H atoms geometrically according to a reasonable chemical structure for capecitabine, which shows the tautomeric H atom attached to the N atom of the carbamate group and the plausible formation of an intermolecular N—H⋯O hydrogen bond. As shown by Malińska et al. (2014), the H atom is actually located on the N atom of the pyrimidine ring (Fig. 2), thereby forming an intramolecular N—H⋯O link.
With respect to the fact that structure solution from powder diffraction data is based on the proposed molecular structure, readers should beware of the incorrectly placed H atom in Rohlicek et al. (2009) and they should be also beware of the wrong in a single-crystal study of Malińska et al. (2014).
References
Kratochvil, B., Husak, M., Korotkova, E. I. & Jegorov, A. (2016). Chem. Listy, 110, 40–47. Google Scholar
Malińska, M., Krzecyński, P., Czerniec-Michalik, E., Trzcińska, K., Cmoch, P., Kutner, A. & Woźniak, K. (2014). J. Pharm. Sci. 103, 587–593. PubMed Google Scholar
Rohlicek, J., Husak, M., Gavenda, A., Jegorov, A., Kratochvil, B. & Fitch, A. (2009). Acta Cryst. E65, o1325–o1326. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
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