An Efficient Synthesis of Pyrido[2,3‐ d ]pyrimidines and Pyrido[2′,3′:3,4]pyrazolo[1,5‐ a ]pyrimidines as PIM‐1 Kinase Inhibitors

Direct synthesis of a new series of pyrido[2,3‐ d ]pyrimidines and pyrido[2′,3′:3,4]pyrazolo[1,5‐ a ]pyrimidine s via heterocyclization of α‐aminonicotinonitrile was described and fully characterized. The desired pyrido[2,3‐ d ]pyrimidines 2‐7 were synthesized via acylation of α‐aminonicotinonitrile with formamide, acetic anhydride, and formic acid or addition cyclization reaction with phenyl isocyanate, ammonium thiocyanate, and urea, respectively. On the other hand, nicotinonitrile 1 was annulated with hydrazine hydrate, followed by cyclization with acetyl acetone and ethyl cyanoacetate to afford pyrido[2',3':3,4]pyrazolo[1,5‐ a ]pyrimidines 9 and 10 , respectively. All compounds were subjected to cytotoxicity screening against three cancer cell lines: HepG‐2, HCT‐116, and MCF‐7. The most cytotoxic compound, 3 , was subjected to PIM‐1 kinase inhibition and molecular docking to elucidate the virtual binding mechanism with the target. Interestingly, compound 3 demonstrates the most promising cytotoxicity with IC 50 values of 7.67 ± 0.4 µM (HepG‐2), 8.07 ± 0.6 µM (HCT‐116), and 6.90 ± 0.3 µM (MCF‐7), approaching the efficacy of DOX and sorafenib. Compound 3 showed a promising PIM‐1 kinase inhibition with an IC 50 of 0.03 µM, compared to Staurosporine, which had an IC 50 of 0.02 µM. PIM‐1 kinase inhibition was virtually visualized by molecular docking, which highlighted the binding interactions of the lead 3 with the PIM‐1 active site. Accordingly, compound 3 was validated as a PIM‐1‐targeted anti‐cancer agent.