Synthesis of N-substituted 4,6-dioxo-imidazo[3,4-c] thiazoles and their analgesic activity in mice

A new series of N-substituted dioxo-imidazo[3,4-c]thiazoles have been prepa red and evaluated for their analgesic activity. The structures of these new derivatives were confirmed by IR, H-1 NMR and C-13 NMR spectra, and by ele mental analysis. When administered intraperitoneally to mice all derivative s were devoid of any toxic effect, even at the high dose of 800 mg kg(-1). In the phenylbenzoquinone-induced abdominal constriction test in mice, eigh t of the nine synthesized compounds exhibited significant antinociceptive p roperties with ED50 values (50% effective dose) ranging from 46.7 to 104.7 mg kg(-1) intraperitoneally. Further investigation demonstrated that analge sic activity of the most effective derivatives 5e and 5f partly involved op ioidergic and/or noradrenergic pathways.