Synthesis and anti-mitotic activity of 2,4-or 2,6-disubstituted- and 2,4,6-trisubstituted-2H-pyrazolo[4,3-c]pyridines

An efficient synthetic route for the synthesis of 2H-​pyrazolo[4,​3-​c]​pyridines, primarily varying by the substituents at the 2-​, 4- and 6-​positions, is described here. A Sonogashira-​type cross-​coupling reaction was employed to yield 3-​alkynyl-​1H-​pyrazole-​4-​carbaldehydes, ethanones and propanones from the corresponding 1H-​pyrazol-​3-​yl trifluoromethanesulfonates. Subsequent treatment of the coupling products with dry ammonia afforded a versatile library of 2H-​pyrazolo[4,​3-​c]​pyridines, which were then evaluated for their cytotoxicity against K562 and MCF-​7 cancer cell lines. The most potent of these compds. displayed low micromolar GI50 values in both cell lines. Active compds. induced dose-​dependent cell-​cycle arrest in mitosis, as shown by flow cytometric anal. of DNA content and phosphorylation of histone H3 at serine-​10. Moreover, biochem. assays revealed increased activities of caspases-​3​/7 in treated cells, specific fragmentation of PARP-​1, and phosphorylation of Bcl-​2, collectively confirming apoptosis as the mechanism of cell death.