Different positions of amide side chains on the benzimidazo[1,2-a]quinoline skeleton strongly influence biological activity†
Benzimidazo[1,2-a]quinolines substituted with amide chains have been evaluated for their antiproliferative, antibacterial and antiviral activity in vitro. Amido-substituted cyclic derivatives were synthesized by classical organic synthetic reactions in order to study the influence of the type and length of the amide side chain as well as its position on the tetracyclic skeleton on biological activity. The most promising antiproliferative activity (i.e. sub-micromolar IC50 concentrations) was displayed by 6-N,N-dimethylaminopropyl 21, 6-N,N-diethylaminoethyl 22 and the 2- and 6-N,N-dimethylaminopropyl substituted derivative 25. Additionally, micromolar concentrations of compounds 21 and 25 induced apoptosis in human cervical carcinoma HeLa cells. Compounds 28, 29 and 30, substituted with the isobutyl, N,N-dimethylaminopropyl and N,N-diethylaminoethyl amide side chain placed at position 2, displayed antiviral activity against herpes simplex virus (HCV) (EC50 1.8–6.8 μM) and human coronavirus (EC50 4–12 μM). Furthermore, N,N-dimethylaminopropyl 21 and N,N-diethylaminoethyl 22 substituted compounds bearing the amide side chain at position 6 of the tetracyclic skeleton were active against S. epidermidis and C. albicans strains.