design, synthesis, and biologicalevaluation of constrained aminopyridinylimidazoles as p38α MAP kinase inhibitors. The frozen analogue approach focused on the pyridinyl unit, using purine bioisosteres as constrained structureanalogues. The identification of the most potent bioisostere was followed by a further derivatization to address hydrophobic region II. In combination with C-2 modifications of the