Design and Synthesis of Celecoxib and Rofecoxib Analogues as Selective Cyclooxygenase-2 (COX-2) Inhibitors: Replacement of Sulfonamide and Methylsulfonyl Pharmacophores by an Azido Bioisostere

Celecoxib (13) and rofecoxib (17) analogues, in which the respective SO2NH2 and SO2Me hydrogen-bonding pharmacophores were replaced by a dipolar azido bioisosteric substituent, were investigated. Molecular modeling (docking) studies showed that the azido substituent of these two analogues (13, 17) was inserted deep into the secondary pocket of the human COX-2 binding site where it undergoes electrostatic interaction with Arg513. The azido analogue of rofecoxib (17), the most potent and selective inhibitor of COX-2 (COX-1 IC50 = 159.7 μM; COX-2 IC50 = 0.196 μM; COX-2 selectivity index = 812), exhibited good oral antiinflammatory and analgesic activities.