Synthesis, characterization and biological evaluation of some newer carbazole derivatives

A series of novel 5-[(9H-carbazol-9-yl)methyl]-N-[(substituted phenyl)(piperazin-1-yl)methyl]-1,3,4-oxadiazol-2-amines (4a–o) derivatives was synthesized by starting with carbazole, which on reaction with ethyl chloroacetate yielded ethyl 2-(9H-carbazole-9-yl)acetate (1). Compound 1 on reaction with semicarbazide followed by cyclisation with sulphuric acid gave 5-((9H-carbazole-9-yl)-1,3,4-oxadiazol-2-amine (3), which through Mannich reaction with piperazine and a variety of aromatic aldehydes in the presence of acetic acid yielded the titled compounds (4a–o). The structures of compounds were characterized by UV, FT-IR, 1H-NMR and MS spectral studies, and by elemental analysis. All the derivatives were evaluated for their antibacterial, antifungal and anticancer activities. Among the tested compounds, 4a, 4d, 4e and 4n exhibited significant antibacterial and antifungal activity, while the compounds 4a, 4d, 4k and 4n were found to be active on the human breast cancer cell line MCF7.