Synthesis and antiviral activity of new pyrazole and thiazole derivatives

New N-acetyl (5–8) and N-thiocarbamoyl (9–12) derivatives of 4,5-dihydropyrazole were synthesized starting from α,β-unsaturated ketones under the effect of hydrazine hydrate and thiosemicarbazide, respectively. N-Thiocarbamoylpyrazole derivatives (9–12) were cyclized using either ethyl bromoacetate or phenacyl bromides to afford the novel pyrazolothiazol-4(5H)-ones (13–16) or pyrazolothiazoles (17–24). The antiviral activity for such novel compounds against a broad panel of viruses in different cell cultures revealed that N-acetyl 4,5-dihydropyrazole 7 was the only active one at subtoxic concentrations against vaccinia virus (Lederle strain) in HEL cell cultures with a 50% effective concentration (EC50) value of 7 μg/ml.

Graphical abstract In the search for effective antiviral agents, new N-acetyl pyrazole (5–8), pyrazolothiazolone (13–16) and pyrazolothiazole (17–24) derivatives were synthesized and evaluated against a broad panel of viruses using different cell cultures whereas N-acetyl pyrazole (7) showed the best antiviral activity against vaccinia virus (Lederle strain) in HEL cell cultures with an EC50 value of 7 μg/ml.Figure optionsDownload full-size imageDownload as PowerPoint slide