The present invention relates to a compound of the formula (I) wherein R1 is benzofuranyl substituted by halogen, or styryl substituted by halogen; R2 is substituted hydroxy, substituted mercapto or substituted sulfonyl; and X is or pharmaceutically acceptable salts thereof. The compound (1) of the present invention and pharmaceutically acceptable salts thereof possess a strong inhibitory activity on the production of nitric oxide (NO), and are useful for prevention and/or treatment of NO-mediated diseases in human being and animals ##STR00001##