Regioselective synthesis of 2- and 4-diarylpyridine ethers and their inhibitory activities against phosphodiesterase 4B

Two diaryl ether regioisomers of pyridine were prepared through the CuI/TMEDA/Cs2CO3-catalyzed reaction of 2,4-dibromopyridine with phenol derivatives under nitrogen atmosphere. The polar solvent DMSO gave 4-isomer as the major product whereas less polar toluene resulted in 2-isomer as a major product. Structures of regioisomers were confirmed by single crystal X-ray diffraction analysis. 4-regioisomer shows higher biological activity against phosphodiesterase 4B (PDE4B) than that of 2-isomer. Molecular docking simulations revealed that the PDE4B-inhibitory activity difference between the two regioisomers was mainly attributed to the atomic charge difference on the –O– linker.