Synthesis and Antiproliferative Activity of 2,6-Disubstituted Imidazo[4,5-b]pyridines Prepared by Suzuki Cross Coupling

A series of novel 2,6-diphenyl substituted imidazo[4,5-b]pyridines was designed and synthesized using optimized Suzuki cross coupling to evaluate their biological activity in vitro. The conditions of the Suzuki coupling were evaluated and optimized using a model reaction. To study the influence of the substituents on the biological activity, we prepared N-unsubstituted and N-methyl substituted imidazo[4,5-b]pyridines with different substituents at the para position on the phenyl ring placed at position 6 on the heterocyclic scaffold. Antiproliferative activity was determined on diverse human cancer cell lines, and the selectivity of compounds with promising antiproliferative activity was determined on normal peripheral blood mononuclear cells (PBMC). Pronounced antiproliferative activity was observed for p-hydroxy substituted derivatives 13 and 19, both displaying strong activity against most of the tested cell lines (IC(50) 1.45–4.25 μM). The unsubstituted N-methyl derivative 19 proved to be the most active derivative. There was a dose-dependent accumulation of G2/M arrested cells in several cancer cell lines after exposure to compound 19, implying a cell cycle-phase-specific mechanism of action. Additionally, the novel series of derivatives was evaluated for antiviral activity against a broad panel of viruses, yet the majority of tested compounds did not show antiviral activity.