A compound represented by the formula (I) or a pharmaceutically acceptable salt thereof:wherein Z represents nitrogen atom, C—F or the like R1 represents a C1-C3 alkyl groupY represents oxygen atom or N—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).
