The purine ring is a critical structural element in several effector molecules (such as agonists, antagonists and substrates) that play a key role in numerous cellular processes. 1., 2., 3. and 4. An example of such an inhibitor is Olomoucine (1), which exhibits a moderate activity (IC 50 =7 μM) towards cdk-2. Despite this moderate activity, the 2,6,9-trisubstituted purine is an ideal scaffold for the generation of kinase inhibitor libraries. Consequently, combinatorial ...