The present invention relates to a compound of the formula [I]: wherein (a), in which --Y--, R.sup.4, R.sup.5 and R.sup.6 are.sup.4 R.sup.5 each as defined in the description, etc., R.sup.1 is hydrogen, halogen, lower alkyl, hydroxy, etc., R.sup.2 is hydrogen, lower alkyl or hydroxy(lower)alkyl, R.sup.3 is hydrogen or an amino protective group, 20.sup.R7 is hydrogen, lower alkyl, cyclo(lower)alkyl, lower R9 alkenyl, -Z-R.sup.9 or (b), in which -Z- is -0-, --S--, R.sup.9--SO-- or --SO.sub.2--, and each R.sup.9 is independently hydrogen, lower alkyl, cyclo(lower)alkyl, etc., and R.sup.8 is -D-E-R.sup. , in which -D- is --CONHSO.sub.2-- or --S0.sub.2NHCO--, E is bond or lower alkylene, and R.sup.10 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.