Synthesis of novel celecoxib analogues by bioisosteric replacement of sulfonamide as potent anti-inflammatory agents and cyclooxygenase inhibitors

Two series of celecoxib analogues having 1,5-diaryl relationship were synthesized. The key strategy of the molecular design was oriented towards exploring bioisosteric modifications of the sulfonamide moiety of celecoxib. First series (2a–2i) of celecoxib analogues bearing cyano functionality in place of sulfonamide moiety was synthesized by the reaction of appropriate trifluoromethyl-β-diketones (5a–5i) with 4-hydrazinylbenzonitrile hydrochloride (4) in ethanol. Cyano moiety of pyrazoles 2 was then converted into corresponding carbothioamides 3 by bubbling H₂S gas in the presence of triethylamine. All the synthesized compounds (2a–2i and 3a–3i) were screened for their in vivo anti-inflammatory (AI) activity using carrageenan-induced rat paw edema assay. COX-1 and COX-2 inhibitory potency was evaluated through in vitro cyclooxygenase (COX) assays. Compounds 2a, 2b, 2c, 2e and 3c showed promising AI activity at 3–4 h after the carrageenan injection that was comparable to that of the standard drug indomethacin. Although compounds 3d, 3e and 3f exhibited more pronounced COX-2 inhibition but they also inhibit COX-1 effectively thus being less selective against COX-2. Three compounds 2a, 2f and 3a were found to have a COX profile comparable to the reference drug indomethacin. However 2e, 3b, 3c and 3i compounds were the most potent selective COX-2 inhibitors of this study with 3b showing the best COX-2 profile. In order to better rationalize the action and the binding mode of these compounds, docking studies were carried out. These studies were in agreement with the biological data.