Pyrimido[4,5-b]quinoline-2-thiol/ol: microwave-induced one-pot synthesis, DNA binding and cleavage studies

Abstract

This article describes the synthesis of pyrimido[4,5-b]quinoline-2-thiol/ol (3a/3b) by microwave irradiation technique. The dynamic interaction of compounds with deoxyribonucleic acid (DNA) was investigated by absorption spectra, viscosity measurements, and thermal denaturation studies. Intrinsic binding constants (K _b ) had values 3.1×10⁶ for 3a and 2.3×10⁵ for 3b. The proposed DNA binding mode supports the large enhancement in the relative viscosity of calf thymus (CT-DNA) on binding to compounds. Results suggest that 3a/3b can bind to CT-DNA by intercalation via the aromatic ring into the base pairs of DNA. Moreover, efficient DNA damage was observed on oxidative cleavage in the presence of 3a/3b.

Keywords:

• pyrimidoquinolines
• microwave irradiation
• CT-DNA binding
• oxidative cleavage
• viscosity–thermal

Acknowledgements

The author H.R. Prakash Naik is thankful to NMR research centre, Indian Institute of Science, Bangalore, for spectral facilities, and to SC/ST cell, Kuvempu University, for awarding Junior Research Fellowship (JRF).