Synthesis and Antiinflammatory and Analgesic Properties of 2-Amino-1H-benzimidazole and 1, 2-Dihydro-2-iminocycloheptimidazole Derivatives

Abstract

2-Amino-1H-benzimidazoles (3) and 1, 2-dihydro-2-iminocycloheptimidazoles (4) were synthesized and evaluated for antiinflammatory and analgesic activities. The compounds in the series 3 were synthesized via phenylthioureas (6) or 2-chloro-1H-benzimidazole (12). Most of 4 were synthesized by two methods. One was the reaction of carbodiimides (14) with 2-amino-2, 4, 6-cycloheptatrien-1-one (method A). The other was the reaction of guanidines (15) with 2-chloro-2, 4, 6-cycloheptatrien-1-one (method B). Some of the compounds 3 and 4 exhibited potent antiinflammatory and analgesic activities when compared to timegadine (1) or tiaramide hydrochloride (HCl) (17). It was of interest that 1-(2-benzothiazolyl)-2-cyclohexylimino-1, 2-dihydrocycloheptimidazole (4e) showed superior analgesic activity to timegadine or tiaramide HCl (ED₅₀=1.7 mg/kg p.o. in the acetic acid-induced writhing test, ED₃₀=14.0 mg/kg p.o. in Randall-Selitto method) in spite of no effect on prostaglandin E₂ synthesis.