Diastereoselective synthesis and profiling of bicyclic imidazolidinone derivatives bearing a difluoromethylated catechol unit as potent phosphodiesterase 4 inhibitors.

Metal-mediated C-H functionalization of cyclic N-oxides was exploited to access a series of new difluoromethylated analogs of imidazolidinone-based PDE4 inhibitor CMPI in a diastereoselective manner. Among the products synthesized, compounds with fine-tuned activity/selectivity profiles compared to both CMPI and the clinically applied apremilast were identified. From these studies, an unusual fused 1,2-oxazinoimidazolidinone heterocyclic system was suggested as a novel scaffold for the design of potent and selective PDE4 inhibitors. Computational studies suggest that the oxygen atom in the imidazolidinone unit can bind to the metal ion center (most likely Mg2+). DFT calculations of the relative interaction energies of inhibitors with Mg2+ and Zn2+ ions were performed on a model of the bimetal active site of PDE4.