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Molecules 2018, 23(1), 161; https://doi.org/10.3390/molecules23010161

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

1
NMR laboratory, Institute of Organic Chemistry Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
2
Department of Chemistry, Pharmaceutical Research Institute, Rydygiera 8, 01-793 Warsaw, Poland
3
Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
*
Author to whom correspondence should be addressed.
Received: 17 November 2017 / Revised: 4 January 2018 / Accepted: 12 January 2018 / Published: 13 January 2018
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Abstract

The molecular structure of capecitabine (a widely applied prodrug of 5-fluorouracil) was studied by multinuclear NMR measurements and DFT quantum mechanical calculations. One or two tautomeric forms in a solution were detected depending on the solvent used. In the organic solvents, a mixture of two forms of capecitabine was observed: carbamate and imine tautomers. In the aqueous solution, only the carbamate form was found. The methylation of capecitabine yields mainly two products in different proportions: N3-methylcapecitabine and N7-methylcapecitabine. The protonation of capecitabine in organic solvents with perchloric acid occurs at the N3 nitrogen atom. DFT calculations strongly support the results coming from the analysis of the NMR spectra. View Full-Text
Keywords: capecitabine; tautomers; proton exchange; 1H-, 13C-, 15N-NMR; DFT capecitabine; tautomers; proton exchange; 1H-, 13C-, 15N-NMR; DFT
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Cmoch, P.; Krzeczyński, P.; Leś, A. Multinuclear NMR Measurements and DFT Calculations for Capecitabine Tautomeric Form Assignment in a Solution. Molecules 2018, 23, 161.

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