Capecitabine from X-ray powder synchrotron data. Corrigendum

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 crystal structure 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 enantiomer in a single-crystal study of Malińska et al. (2014).