Crystal Structure and Tautomerism of Capecitabine

Capecitabine from X-ray powder synchrotron data. Corrigendum

“…As shown by Maliń ska et al (2014), the H atom is actually located on the N atom of the pyrimidine ring (Fig. 2), thereby forming an intramolecular N-HÁ Á ÁO link.…”

“…Following our powder-diffraction study of capecitabine (Rohlicek et al, 2009), Maliń ska 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 ISSN 2056-9890 Figure 1 Overlay of the capecitabine molecular structures arising from powder diffraction (blue) and from single-crystal diffraction data (red).…”

“…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 Maliń ska et al (2014).…”

Multinuclear NMR Measurements and DFT Calculations for Capecitabine Tautomeric Form Assignment in a Solution

“…Although use of capecitabine is widely described, especially in pharmacological and medical literature, a proper and correct notation of its molecular structure is still a matter of debate. The literature concerning capecitabine structure is rather poorly documented and only a few papers dealing with its synthesis are accessible [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. From these previous papers presenting the synthesis of 1 and its 1 H-NMR spectra, it appears that the organic solutions of capecitabine undergo a dynamic process.…”

“…In 2009 Rohliček and co-workers [ 11 ], using synchrotron radiation at 293 K, reported the crystal structure of capecitabine 1 from the powder diffraction data as structure 1 ( Figure 1 ). A few years later, our group [ 14 ] corrected the structure of capecitabine by presenting the X-ray data and postulated the preferred structure of capecitabine as an imine tautomer II with the -C(=O)-O-C 5 H 11 chain rotated around the C4-N7 bond by 180° ( Figure 3 ).…”