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Influence of the Solvent on the Stability of Aminopurine Tautomers and Properties of the Amino Group

Authors :
Anna Jezuita
Paweł A. Wieczorkiewicz
Tadeusz M. Krygowski
Halina Szatylowicz
Source :
Molecules, Vol 28, Iss 7, p 2993 (2023)
Publication Year :
2023
Publisher :
MDPI AG, 2023.

Abstract

Amino derivatives of purine (2-, 6-, 8-, and N-NH2) have found many applications in biochemistry. This paper presents the results of a systematic computational study of the substituent and solvent effects in these systems. The issues considered are the electron-donating properties of NH2, its geometry, π-electron delocalization in purine rings and tautomeric stability. Calculations were performed in ten environments, with 1 < ε < 109, using the polarizable continuum model of solvation. Electron-donating properties were quantitatively described by cSAR (charge of the substituent active region) parameter and π-electron delocalization by using the HOMA (harmonic oscillator model of aromaticity) index. In aminopurines, NH2 proximity interactions depend on its position and the tautomer. The results show that they are the main factor determining how solvation affects the electron-donating strength and geometry of NH2. Proximity with the NH∙∙∙HN repulsive interaction between the NH2 and endocyclic NH group results in stronger solvent effects than the proximity with two attractive NH∙∙∙N interactions. The effect of amino and nitro (previously studied) substitution on aromaticity was compared; these two groups have, in most cases, the opposite effect, with the largest being in N1H and N3H purine tautomers. The amino group has a smaller effect on the tautomeric preferences of purine than the nitro group. Only in 8-aminopurine do tautomeric preferences change: N7H is more stable than N9H in H2O.

Details

Language :
English
ISSN :
14203049
Volume :
28
Issue :
7
Database :
Directory of Open Access Journals
Journal :
Molecules
Publication Type :
Academic Journal
Accession number :
edsdoj.87ff0bb1ca234f20aa9a3d7328083f3c
Document Type :
article
Full Text :
https://doi.org/10.3390/molecules28072993