Synthesis of 4-Phenylthieno[2,3-e][1,2,4]triazolo[4,3-a]pyrimidine-5(4H)-one Derivatives and Evaluation of Their Anti-inflammatory Activity

A series of 4-phenylthieno[2,3-e][1,2,4]triazolo[4,3-a]pyrimidine-5(4H)-ones (5a–p) with triazole or other heterocyclic substituents (6–11) was synthesized and the compounds were evaluated for their anti-inflammatory activity using the xylene-induced ear-edema test. Pharmacological analyses showed that the compound 4-(4-chlorophenyl)thieno[2,3-e][1,2,4]triazolo[4,3-a]pyrimidine- 5(4H)-one (5m) exhibited the greatest anti-inflammatory activity (50.48% inhibition, 30 min after intraperitoneal administration) and was more potent than the reference drug, indomethacin. The peak activity of 5m was observed 4 h after oral administration, and it showed a higher anti-inflammatory activity than indomethacin did at a dose of 100 mg/kg.