NMR Quantification of Tautomeric Populations in Biogenic Purine Bases

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Authors

BARTL Tomáš ZACHAROVÁ Zuzana SEČKÁŘOVÁ Pavlína KOLEHMAINEN Erkki MAREK Radek

Year of publication 2009
Type Article in Periodical
Magazine / Source European Journal of Organic Chemistry
MU Faculty or unit

Faculty of Science

Citation
Web DOI: 10.1002/ejoc.200801016
Doi http://dx.doi.org/10.1002/ejoc.200801016
Field Organic chemistry
Keywords Purine; Adenine; Low-temperature NMR; Tautomerism; Population
Attached files
Description Purine bases such as purine, adenine, hypoxanthine, and mercaptopurine are known to exist in several tautomeric forms. Characterization of their tautomeric equilibria is important not only for predicting the regioselectivity of their N-alkylation reactions but also for gaining knowledge of the patterns with which these compounds of significant biological activity form hydrogen bonds with their biological targets. Low-temperature 1H- and 13C-NMR spectroscopy were used to investigate the tautomeric equilibria for purine and some purine derivatives in methanol and N,N-dimethylformamide solutions. The N(7)H and N(9)H tautomeric forms were quantified by integrating the individual 1H NMR signals at low temperatures. The Gibbs free energy differences were calculated, and the effects of substitution on the N(7)H/N(9)H ratio discussed. A previously published theoretically predicted mechanism of the tautomeric exchange is compared with our measurements in deuterated solvents. The influence of concentration on the temperature of coalescence indicates that supramolecular clusters play a significant role in this proton transfer process.
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