Aminopurvalanol A is a competitive, selective and cell-permeable inhibitor of cyclin-dependent kinase (CDK) that potently inhibits Cyclin A/cdk2, Cyclin B/cdk1, Cyclin E/cdk2, and P35/cdk5 with IC50 of 33 nM, 33 nM, 28 nM and 20 nM, respectively.