The present invention relates to a compound of the formula [I]: wherein (a), in which &mdashY&mdash, R4, R5 and R6 are4 R5 each as defined in the description, etc., R1 is hydrogen, halogen, lower alkyl, hydroxy, etc., R2 is hydrogen, lower alkyl or hydroxy(lower)alkyl, R3 is hydrogen or an amino protective group, 20R7 is hydrogen, lower alkyl, cyclo(lower)alkyl, lower R9 alkenyl, &mdashZ&mdashR9 or (b), in which &mdashZ&mdash is &mdash0&mdash, &mdashS&mdash, R9 &mdashSO&mdash or &mdashSO2&mdash, and each R9 is independently hydrogen, lower alkyl, cyclo(lower)alkyl, etc., and R8 is -D-E-R10, in which -D- is &mdashCONHSO2&mdash or &mdashS02NHCO&mdash, E is bond or lower alkylene, and R10 is halogen, cyano, carboxy, etc., or a prodrug thereof or a salt thereof. The compound [I] of the present invention and pharmaceutically acceptable salts thereof are useful for the prophylactic and/or the therapeutic treatment of ulcer, overactive bladder, and the like.
