Synthesis and Anticancer and Antiviral Activities of New 2-Pyrazoline-Substituted 4-Thiazolidinones

2-(4,5-Dihydropyrazol-1-yl)-thiazol-4-ones (25) have been synthesized starting from 3-phenyl-5-aryl-1-thiocarbamoyl-2-pyrazolines via [2+3]-cyclization with 2-bromopropionic acid, maleic anhydride, N-arylmaleimides, and aroylacrylic acids. The in vitro anticancer activity of , , , , and were tested by the National Cancer Institute. Compounds , , and demonstrated selective inhibition of leukemia cell lines growth at a single concentration (105 M). The screening of antiviral activity for a broad panel of viruses revealed that N-(4-methoxyphenyl)-2-{2-[5-(4-methoxyphenyl)-3-phenyl-4,5-dihydropyrazol-1-yl]-4-oxo-4,5-dihydrothiazol-5-yl}-acetamide was highly active against Tacaribe TRVL 11 573 virus strain (EC50 = 0.71 g/mL, selectivity index = 130).