GSK-3β inhibitor 13 (compound 47) is an orally active and potent GSK-3β inhibitor with blood-brain permeability. GSK-3β inhibitor 13 inhibits GSK-3β and GSK-3α with IC 50 s of 0.73 nM and 0.35 nM, respectively. GSK-3β inhibitor 13 significantly decreases the phosphorylation of tau ( IC 50 =58 nM), which leads the formation of the neurofibrillary tangles associated with Alzheimer's disease.