Density functional study of anionic allopurinol tautomers

Costas, Marı́a Eugenia; Acevedo‐Chávez, Rodolfo

doi:10.1016/s0166-1280(01)00360-8

Cited by 7 publications

(10 citation statements)

References 21 publications

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“…Knowledge of their tautomeric equilibria is of great importance because this phenomenon affects the behavior of these compounds, from their chemical and spectral properties to their biological activities. [6] According to quantum chemical calculations [7] and experimental IR, UV, [8] and NMR studies, [9] N(7)H and N(9)H represent the favored tautomers of purine derivatives (Scheme 1) as compared with the N(1)H and N(3)H forms. The relative populations of the individual tautomers are generally influenced by the substitution of the purine ring, the solvent, and the temperature.…”

Section: Introductionmentioning

confidence: 99%

NMR Quantification of Tautomeric Populations in Biogenic Purine Bases

Bartl¹,

Zacharová²,

Sečkářová³

et al. 2009

Eur J Org Chem

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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. The tautomeric equilibria of purine and some purine derivatives in methanol and N,N‐dimethylformamide solutions were investigated by low‐temperature 1H and 13C NMR spectroscopy. 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 deuteriated solvents. The influence of concentration on the temperature of coalescence indicates that supramolecular clusters play a significant role in this proton transfer process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Section: Introductionmentioning

confidence: 99%

NMR Quantification of Tautomeric Populations in Biogenic Purine Bases

Bartl¹,

Zacharová²,

Sečkářová³

et al. 2009

Eur J Org Chem

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“…The 1 H and 13 C NMR chemical shifts of the individual atoms were obtained from the corresponding 1D NMR spectra; the 15 N NMR chemical shifts were determined indirectly from 2D inverse-detected 1 H- 15 N chemical shift correlation experiments adjusted for multiple-bond interactions. The assignments of the NMR resonances to individual atoms in the purine skeleton were based on the interpretation of the indirect nuclear spin-spin coupling constants n J H-C and n J H-N , as reported in our previous studies.…”

Section: Resultsmentioning

confidence: 99%

“…The assignments of the NMR resonances to individual atoms in the purine skeleton were based on the interpretation of the indirect nuclear spin-spin coupling constants n J H-C and n J H-N , as reported in our previous studies. 26,27 The 1 H, 13 C, and 15 N NMR chemical shifts for compounds 1 and 2 in dimethylsulfoxide-d 6 (DMSO-d 6 ) are summarized in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…The calculated and experimental data are in good agreement. The final root-mean-square deviations (RMSD) are in the range 1.2-4.8 ppm for the 15 N chemical shifts, and 2.4-3.0 ppm for the 13 C chemical shifts (see Table 3). We observed similar trends in chemical shifts for compounds 2 (and 4).…”

Section: Resultsmentioning

confidence: 99%

“…14 The tautomerism of natural and modified nucleic acid bases with its influence on the biological activity presents an interesting and important topic in chemical biology. 15 Tautomeric forms of modified purines have been extensively investigated by theoretical approaches as well as by experimental techniques, such as X-ray diffraction, NMR, IR, and UV spectroscopy. 16,17 In fact, NMR spectroscopy represents one of the most powerful techniques for investigating tautomerism in the solution.…”

Section: Introductionmentioning

confidence: 99%

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Interpretation of substituent effects on 13C and 15N NMR chemical shifts in 6-substituted purines

Standara

Bouzková

Straka

et al. 2011

Phys. Chem. Chem. Phys.

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A range of purine derivatives modified at position 6 of the basic purine skeleton exhibit a variety of biological activities. Several derivatives are used or tested nowadays for pharmacological treatments. The present work aims to analyze the effects of substituents on the electron distribution in the purine core as reflected by NMR chemical shifts. We collected a comprehensive set of experimental NMR data for a variety of 6-substituted purines (-NH(2), -NHMe, -NMe(2), -OMe, -Me, -CCH, and -CN) and determined the molecular and crystal structures of three derivatives (-NHMe, -CCH, and -CN) by X-ray diffraction. The density-functional methods calibrated in our recent study (Phys. Chem. Chem. Phys., 2010, 12, 5126) have been employed to enable understanding of the substituent-induced changes in the NMR chemical shifts of the atoms in the purine skeleton. Analyses of the nuclear shielding using localized molecular orbitals (LMOs), specifically the natural LMOs (NLMOs) and Pipek-Mezey LMOs, were used to break down the values of the isotropic (13)C and (15)N NMR chemical shifts and the chemical shift tensors into the contributions of the individual LMOs. The experimental and calculated trends in the chemical shift of the N-3 atom correlate nicely with the Hammett constants (σ(para)) and the calculated natural charges on N-3, whereas the contributions of the LMOs to the N-1 and C-6 chemical shifts are found to be more complex.

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Computational prediction of vibrational spectra of normal and modified DNA nucleobases

Shanmugasundaram¹,

Puranik²

2009

J Raman Spectroscopy

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Purines, pyrimidines, and the corresponding ribose monophosphates are ubiquitous biomolecules involved in several cellular processes-in DNA and RNA, signaling, and energy transactions. In the new and exciting field of DNA-inspired nanostructures, they are used as fundamental building blocks. Unique features of the nucleobases are that several tautomeric states are close in energy and the tautomeric equilibria are sensitive to exocyclic substitution and pH. Knowing the exact structure and tautomer(s) at physiological conditions is crucial to understand the substrate specificities and catalytic mechanisms of the many enzymes for which these nucleobases are substrates. Very few spectroscopic methods can distinguish between tautomers and provide solution structures. Vibrational spectroscopy has long been known to be an excellent tool to obtain reliable information on nucleic acids. However, even when good-quality spectra are available, isotope editing is required to make reliable band assignments and identify structures unequivocally. Density functional theoretical (DFT) methods have become indispensible in assisting the assignment of observed spectra to normal modes, identification of tautomers, and modeling of spectra of isotope-edited molecules. We review the performance of DFT methods in the prediction of nucleobases and their analogs. We find that even with modest basis sets, trends in vibrational spectra can be predicted adequately and guide assignments to normal modes of the molecule. Shifts in band positions induced upon isotope labeling are reproduced more reliably than the band positions. Scaling considerably improves the agreement between the computed and experimental spectra, but accurate prediction of vibrations of exocyclic groups like C O requires that solvent effects are taken into account.

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Density functional study of anionic allopurinol tautomers

Cited by 7 publications

References 21 publications

NMR Quantification of Tautomeric Populations in Biogenic Purine Bases

NMR Quantification of Tautomeric Populations in Biogenic Purine Bases

Interpretation of substituent effects on 13C and 15N NMR chemical shifts in 6-substituted purines

Computational prediction of vibrational spectra of normal and modified DNA nucleobases

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