DNA threading agents: effect of sidechain bulk on DNA binding and cytotoxicity of 9-anilinoacridine-4-carboxamides

A series of 9-anilinoacridine-4-carboxamides with cycloalkyl sidechains has been synthesised to study the effect of sidechain bulk on the DNA binding properties and biological activity of these potential threading intercalators. With sidechains larger than cyclohexane the pKa of the acridine is exceptionally low, so that DNA binding is restricted to pHs below 5. The compounds are cytotoxic to human colon carcinoma cells in the μM range irrespective of their ability to bind to DNA.