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Structural and solvent effects on the 13 C and 15 N NMR chemical shifts of indoloquinoline alkaloids: experimental and DFT study
Author(s) -
Toušek Jaromír,
Van Miert Sabine,
Pieters Luc,
Van Baelen Gitte,
Hostyn Steven,
Maes Bert U. W.,
Lemière Guy,
Dommisse Roger,
Marek Radek
Publication year - 2008
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2125
Subject(s) - chemistry , density functional theory , chemical shift , solvent , intermolecular force , computational chemistry , solvent effects , nuclear magnetic resonance spectroscopy , intercalation (chemistry) , molecule , macromolecule , proton nmr , crystallography , stereochemistry , organic chemistry , biochemistry
Indoloquinoline alkaloids represent an important class of antimalarial, antibacterial and antiviral compounds. They have been shown to bind to DNA via intercalation preferentially at GC‐rich sequences containing nonalternating CC sites. The stability of complexes formed with biological macromolecules depends on noncovalent binding. In the present study, the ability of indoloquinolines to form intermolecular interactions with solvents was investigated by using NMR spectroscopy and density functional theory (DFT) (B3LYP/6‐31G**) calculations. NMR data measured for indoloquinoline bases and the corresponding hydrochlorides are discussed in relation to the structure. DFT calculations of shielding constants in vacuo and in solution allowed the investigation of the influence of the environment on the NMR parameters. Calculations incorporating solvent effects indicated significant changes in the anisotropy of the electron distribution, reflected in the span of the chemical shielding tensor (Ω = σ 11 − σ 33 ). Solvent effects on the span of the 13 C and 15 N shielding tensor depended on the type of atom and the data indicated a significant influence of solute‐solvent interactions. Copyright © 2008 John Wiley & Sons, Ltd.