2-Aminopyrazolo[1,5- a]pyrimidines as potent and selective inhibitors of JAK2

The discovery and structure based optimization of a novel series of 2-amino-pyrazolo[1,5- a]pyrimidines of potent and selective inhibitors of JAK2 is described. Constitutive activation of the EPO/JAK2 signaling cascade has recently been implicated in a variety of myeloproliferative disorders including polycythemia vera, essential thrombocythemia and myelofibrosis. In an effort to uncover therapeutic potential of blocking the EPO/JAK2 signaling cascade, we sought to discover selective inhibitors that block the kinase activity of JAK2. Herein, we describe the discovery and structure based optimization of a novel series of 2-amino-pyrazolo[1,5- a]pyrimidines that exhibit potent inhibition of JAK2.