title: Synthesis and biological evaluation of linear phenylethynylbenzenesulfonamide regioisomers as cyclooxygenase-1/-2 (COX-1/-2) inhibitors.
abstract: A group of regioisomeric phenylethynylbenzenesulfonamides possessing a COX-2 SO2NH2 pharmacophore at the para-, meta- or ortho-position of the C-1 phenyl ring, in conjunction with a C-2 substituted-phenyl (H, OMe, OH, Me, F) group, were synthesized and evaluated as inhibitors of the cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) isozymes. The target 1,2-diphenylacetylenes were synthesized via a palladium-catalyzed Sonogashira cross-coupling reaction. In vitro COX-1/-2 isozyme inhibition structure-activity data showed that COX-1/-2 inhibition and the COX selectivity index (SI) are sensitive to the regioisomeric placement of the COX-2 SO2NH2 pharmacophore where the COX-2 potency order for the benzenesulfonamide regioisomers was generally meta>para and ortho. Among this group of compounds, the in vitro COX-1/-2 isozyme inhibition studies identified 3-(2-phenylethynyl)benzenesulfonamide (10a) as a COX-2 inhibitor (COX-2 IC50=0.45 microM) with a good COX-2 selectivity (COX-2 SI=70). In contrast, 2-[2-(3-fluorophenyl)ethynyl]benzenesulfonamide (11c) possessing a SO2NH2 COX-2 pharmacophore at the ortho-position of the C-1 phenyl ring exhibited COX-1 inhibition and selectivity (COX-1 IC50=3.6 microM). A molecular modeling study where 10a was docked in the binding site of COX-2 shows that the meta-SO2NH2 COX-2 pharmacophore was inserted inside the COX-2 secondary pocket (Arg513, Phe518, Val523, and His90). Similar docking of 10a within the COX-1 binding site shows that the meta-SO2NH2 pharmacophore is unable to interact with the respective amino acid residues in COX-1 that correspond to those near the secondary pocket in COX-2 due to the presence of the larger Ile523 in COX-1 that replaces Val523 in COX-2.
authors.affiliation: Lakeland College, Lloydminister, Alta., Canada S9V 1Z3.
authors.forename: Raymond
authors.initials: R
authors.lastname: Anana
authors.forename: P N Praveen
authors.initials: PN
authors.lastname: Rao
authors.forename: Qiao-Hong
authors.initials: QH
authors.lastname: Chen
authors.forename: Edward E
authors.initials: EE
authors.lastname: Knaus
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D018360:Crystallography, X-Ray; D051545:Cyclooxygenase 1 / Q000187:drug effects*; D051546:Cyclooxygenase 2 / Q000187:drug effects*; D016861:Cyclooxygenase Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D004353:Drug Evaluation, Preclinical; D006614:Hindlimb / Q000187:drug effects; D066298:In Vitro Techniques; D008958:Models, Molecular; D015394:Molecular Structure; D051381:Rats; D012756:Sheep; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013449:Sulfonamides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D000096926:Benzenesulfonamides
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D016861:Cyclooxygenase Inhibitors; D013449:Sulfonamides; C513023:phenylethynylbenzenesulfonamide; D000096926:Benzenesulfonamides