Crystal of pyrido [3,4-d] pyrimidine derivatives having CDK4 / 6 inhibitory activity.Crystal of the compound represented by equation (I).In formula (I), R1 represents h, etc., R2 represents h, l represents a single bond, and X represents ch or n.No selection【課題】CDK4/6阻害活性を有するピリド[3,4-d]ピリミジン誘導体の結晶。【解決手段】式(I)で表される化合物の結晶。式(I)中、R1はH等、R2はH等、Lは単結合等、XはCH又はNを表す。【選択図】なし