Novel purine‐2,6‐diamine derivatives were designed and synthesized as cyclin‐dependent kinase (CDK) inhibitors. According to the preliminarybiologicalevaluation, most of the compounds show good inhibitory activities in CDK1 enzyme assay and potent antiproliferative activities in some tumor cell lines. Especially, compound 11a (IC50=0.35 µmol/L for CDK1/cyclin B and IC50=0.023 µmol/L for CDK2/cyclin