Synthesis and SAR/3D-QSAR studies on the COX-2 inhibitory activity of 1,5-diarylpyrazoles to validate the modified pharmacophore

Diverse analogs of 1,5-diarylpyrazoles having 3-hydroxymethyl-4-sulfamoyl (SO2NH2)/methyl sulfonyl (SO2Me)-pheny group at N1 were synthesized and evaluated for their in vitro cyclooxygenase (COX-1/COX-2) inhibitory activity. The SAR study mainly involved the variations at positions C-3, C-5 and N1 of the pyrazole ring. Several small hydrophobic groups at/around position-4 of C-5 phenyl, viz. 3,4-dimethylphenyl analog 9, 3-methyl-4-methylsulfanylphenyl analog 14 and 2,3-dihydrobenzo[b]thiophenyl analog 17, exhibited impressive COX-2 inhibitory potency. In general, the sulfonamide analogues with a CHF2 at C-3 were found to be more potent than those having a CF3 group. The three dimensional quantitative structure activity relationship comprising comparative molecular field analysis (3D-QSAR-CoMFA) afforded the models with high predictivity which further validated the acceptance of hydroxymethyl (CH2OH) group in the hydrophilic pocket of the COX-2 enzyme.