A series of 1, 4, 6-trisubstituted pyrazolo [3, 4-d] pyrimidines 15–19, 30–38 capable of selectively inhibiting CDK2 activity were synthesized by derivatization at C-4, C-6 and N-1 with various amines and lower alkyl groups. For above synthetic compounds, biological evaluation was carried out and structure–activity relationship was examined. In our series, 4- anilino compounds exhibited better CDK2 inhibitory activity and antitumor activity ...