The present invention provides novel compounds having a P2X 3 and/or P2X 2/3 receptor antagonistic activity. A compound of Formula (I): wherein R a and R b , and R d and R e are taken together to form oxo or the like； R 4a and R 4b are hydrogen or the like； n is 1 or the like； R 2 is aryl or the like； s and s' is 0 or the like； R 9 and R 9' are halogen or the like； R 20a and R 20b are hydrogen, alkyl or the like； u is 1 to 4； R 13 is hydrogen or the like, or its pharmaceutically acceptable salt.本發明係提供一種新穎之具有P2X3及/或P2X2/3受體拮抗作用之化合物。本發明之化合物或其製藥上所容許之鹽係以式(I)表示：[式中，Ra與Rb及Rd與Re一起形成為側氧基等；R4a及R4b為氫等；n為1等；R2為芳基等；s及s'為0等；R9及R9'為鹵素等；R20a及R20b為氫、烷基等；u為1~4；R13為氫等]。
