Solvent-free synthesis of heteroannulated carbazoles: A novel class of anti-tumor agents

•Green synthesis.•In vitro cytotoxicity, HeLa, AGS.•Compound 3b IC50 = 0.37.

A series of novel carbazole analogues that hold pyrido, isoxazolo, pyrimido and pyrazolo templates were designed and synthesised in good yield by grinding conditions. All the synthesised compounds were screened for their anti-tumor activity and displayed enviable selective growth inhibition on HeLa cell line compared to AGS cell line. Among these compounds, compound 2-(3′,4′-diethoxy-benzylidene)-6-methyl-2,3,4,9-tetrahydro-carbazol-1-one,6-chloro-2-(3′,4′-diethoxy-benzylidene)-2,3,4,9-tetrahydro-carbazol-1one, 2-(3′,4′-diethoxy-benzylidene)-8-methyl-2,3,4,9-tetrahydro-carbazol-1-one, 3-(3′,4′-diethoxyphenyl)-7-methyl-4,5-dihydro-10H-isoxazolo[3,4-a]carbazole, 7-chloro-3-(3′,4′-diethoxyphenyl)-4,5-dihydro-10H-isoxazolo[3,4-a]carbazole, 4-(3′,4′-diethoxyphenyl)-2-ethoxy-8-methyl-6,11-dihydro-5H-pyrido[2,3-a]carbazole-3-nitrile, 8-chloro-4-(3′,4′-diethoxyphenyl)-2-ethoxy-6,11-dihydro-5H-pyrido[2,3-a]carbazole-3-nitrile, 4-(3′,4′-diethoxyphenyl)-2-ethoxy-10-methyl-6,11-dihydro-5H-pyrido[2,3-a]carbazole-3-nitrile were found to have promising anti-tumor properities with reference to the standard ellipticine against the HeLa cancer cell line. All these intermediates showed IC50 outranged the standard ellipticine. The same compounds showed moderate activity against AGS cancer cell lines. The efforts were undertaken to optimize potency and selectivity of this class of compounds.

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