The present invention relates to a compound formula [I] wherein R1 and R5 are each independently hydrogen, halogen, lower alkyl, etc., R2 is hydrogen or an amino protective group, x is bond, -o-o, —O—CH2—, etc., y is in which Z is bond, —O—(CH2)m— (in which m is 1 to 4), etc., R3 is lower alkanoyl, carboxy, lower alkoxycarbonyl, etc., and R4 is hydrogen, halogen, hydroxy, phenoxy, lower alkyl, lower alkoxy, etc., and n is 0, 1 or 2, 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 pollakiurea or urinary incontinence.