A compound represented by the formula (I) or a pharmaceutically acceptable salt thereof: wherein Z represents nitrogen atom or C—X; X represents hydrogen atom or fluorine atom; R1 is hydrogen atom or a C1-C3 alkyl group; L represents single bond or a C1-C6 alkylene group which may be substituted; Y represents single bond, sulfur atom, oxygen atom, NH, or the like; R2 represents hydrogen atom or a cyclic group which may be substituted, which is used for preventive and/or therapeutic treatment of a disease caused by abnormal activity of tau protein kinase 1 such as a neurodegenerative diseases (e.g. Alzheimer disease).