A compound represented by the formula (I) or a pharmaceutically acceptable salt thereof: wherein Z represents nitrogen atom, C&mdash；F or the like； R1 represents a C1-C3 alkyl group； Y represents oxygen atom or N&mdash；R7； R2, R3, R4, R5, R6 and R7 each independently represents hydrogen atom, a C1-C6 alkyl group, or a group represented by the formula (II): which is used for preventive and/or therapeutic treatment of a disease caused by tau protein kinase 1 hyperactivity such as a neurodegenerative diseases (e.g. Alzheimer disease).
