abstract |
3,4-d] pyrimidine derivatives having excellent CDK4 / 6 inhibitory activity. A crystal of the compound represented by the formula (I). Wherein R 1 represents a hydrogen atom or a C 1-3 alkyl group, R 2 represents a hydrogen atom or an oxo group, L represents a single bond or a C 1-3 alkylene group, and X represents CH or N. |