Synthesis and bioactivity of novel amino-pyrazolopyridines

Abstract

Here we describe the synthesis and biological activity of novel amino-pyrazolopyridines with anti-NF-κB and pro-apoptotic potential. α-Methylene ketones were used as a starting point for synthesis of amino-pyrazolopyridine 3. The alkylidene malononitriles 1 were obtained by the Knoevenagel reaction of ketones with malononitriles. Vilsmeier-Haack reaction allowed direct access to 2-chloro-3-cyanopyridines 2. Those products, by refluxing with hydrazine hydrate, allowed cyclization to amino-pyrazolopyridines 3a-g, which were not previously described in the literature. Bioactivity results indicated that amino-pyrazolopyridines 3a, 3b and 3g induced apoptotic cell death in K562 cancer cells with an IC50 of 36.5 ± 3.9 μM, 27.6 ± 4.5 μM and 35.0 ± 2.3 μM, respectively, after 72 h. In addition, compounds 3a, 3b and 3g exerted NF-κB inhibition activity with an IC50 of 4.7 ± 1.6 μM, 6.9 ± 1.9 μM and 39.8 ± 3.9 μM, respectively, after 8 h in K562 cells activated with TNFα. Compounds 3b and 3g showed interesting differential toxicity as viability of peripheral blood mononuclear cells (PBMCs) from healthy donors remained largely unaffected by this treatment.

Keywords: Amino-pyrazolopyridine; Apoptosis; Cancer; Inflammation; NF-κB pathway; Vilsmeier–Haack.