Design and synthesis of some substituted thiazolo[3,2-a]pyrimidine derivatives of potential biological activities

In continuation to our previous work, thiazolopyrimidines 2a–x were synthesized through intramolecular cyclization of 2-phenacylthio-dihydropyrimidine hydrobromides 1a–x using polyphosphoric acid. On the other hand, thiazolo[3,2-a]pyrimidine-3-one 3 was coupled with aryldiazonium salts or condensed with isatin to afford compounds 4a–c or 5, respectively. Chemical structure of the target compounds was substantiated by IR, FT-IR, 1H-, 13C and DEPT-13C NMR, MS as well as microanalyses. Moreover, the lipophilicity of the target compounds is expressed as Clog P. The antimicrobial screening of the test compounds 2a–x, 4a–c and 5 revealed moderate activity in comparison to reference drugs. Compounds 2a–c, 2e, 2o and 2v showed a gradual increase in their anti-inflammatory activity reaching its maximum at 5 h compared to indomethacin. Furthermore, the analgesic activity of compounds 2a–c, 2e, 2o and 2v revealed a maximum activity after 5 h of injection compared to aspirin and the LD50 of compounds 2e and 2v was determined.