Synthesis and Biological Evaluation of Benzo [4,5]- and Naphtho[2′,1′:4,5]imidazo[1,2-c]pyrimidinone Derivatives

Azacarbazoles have attracted significant interest due to their valuable properties, such as anti-pathogenic and antitumor activity. In this study, a series of structurally related tricyclic benzo[4,5]- and tertacyclic naphtho[2 ',1 ':4,5]imidazo[1,2-c]pyrimidinone derivatives with one or two positively charged tethers were synthesized and evaluated for anti-proliferative activity. Lead tetracyclic derivative 5b with two amino-bearing arms inhibited the metabolic activity of A549 lung adenocarcinoma cells with a CC50 value of 3.6 mu M, with remarkable selectivity (SI = 17.3) over VA13 immortalized fibroblasts. Cell-cycle assays revealed that 5b triggers G2/M arrest without signs of apoptosis. A study of its interaction with various DNA G4s and duplexes followed by dual luciferase and intercalator displacement assays suggests that intercalation, rather than the modulation of G4-regulated oncogene expression, might contribute to the observed activity. Finally, a water-soluble salt of 5b was shown to cause no acute toxic effects, changes in mice behavior, or any decrease in body weight after a 72 h treatment at concentrations up to 20 mg/kg. Thus, 5b is a promising candidate for studies in vivo; however, further investigations are needed to elucidate its molecular target(s).

Automated summary

Azacarbazoles and its derivatives have significant anti-pathogenic and antitumor activities. This study focused on the synthesis and evaluation of a series of structurally related tetracyclic compounds. The lead derivative, 5b, showed promising anti-proliferative activity against lung adenocarcinoma cells and selectivity towards certain fibroblasts. Further experiments indicated that intercalation might be the mechanism underlying its activity, rather than the modulation of G4-regulated oncogene expression. Additionally, a water-soluble salt form of 5b exhibited no acute toxicity or behavioral changes in mice.