Synthesis and Pharmacological Activities of Novel Bicyclic Thiazoline Derivatives as Hepatoprotective Agents. II. (7-Alkoxycarbonyl-2,3,5,6-tetrahydropyrrolo(2,1-b)thiazol-3-ylidene)acetamide Derivatives.

A series of exomethylenic bicyclic thiazoline derivatives (3a--i) was synthesized and evaluated for hepatoprotective activity against galactosamine-induced and monoclonal antibody-induced acute liver injuries in rats. The structure-activity relationships were investigated. Among the compounds synthesized, N-methyl-(7-isopropoxy-carbonyl-6,6-dimethyl-2,3,5,6- tetrahydropyrrolo[2,1-b]thiazol-3-ylidene)acetamide (3i) exhibited the most potent hepatoprotective activity. This compound suppressed galactosamine-induced hepatic injury at 100 mg/kg by oral administration and further prevented monoclonal antibody-induced hepatic injury at 30 mg/kg by intraperitoneal injection, as judged from the changes in serum transaminase activities.