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Structural and solvent effects on the 13C and 15N NMR chemical shifts of indoloquinoline alkaloids: experimental and DFT study

✍ Scribed by Jaromír Toušek; Sabine Van Miert; Luc Pieters; Gitte Van Baelen; Steven Hostyn; Bert U. W. Maes; Guy Lemière; Roger Dommisse; Radek Marek

Publisher
John Wiley and Sons
Year
2007
Tongue
English
Weight
262 KB
Volume
46
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

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.

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