Anti-HAV activity of some newly synthesized triazolo[4,3-b]pyridazines.

6-Phenyl-[1,2,4]triazolo[4,3-b]pyridazine-3(2H)-thione 2 was used as precursor for the preparation of some novel 3-S-substituted-6-phenyl-[1,2,4]triazolo[4,3-b]pyridazine derivatives 3-11. Furthermore, the preparation of 1-[2-(6-phenyl-[1,2,4]triazolo[4,3-b]pyridazin-3-ylsulfanyl)-acetyl]-1H-pyrazole derivative 13 and 5-(6-phenyl-[1,2,4]triazolo[4,3-b]pyridazin-3-ylsulfanylmethyl)-[1,3,4]oxadiazole derivatives 15 and 17, are described. Some of the prepared products revealed a promising antiviral activity against hepatitis-A virus (HAV, MBB-cell culture adapted strain). Plaque reduction infectivity assay was used to determine virus count reduction as a result of treatment with the test compounds. Compound 15 showed the highest effect on HAV compared to the other tested compounds.