Design and synthesis of new rofecoxib analogs as selective cyclooxygenase-2 (COX-2) inhibitors: replacement of the methanesulfonyl pharmacophore by a N-acetylsulfonamido bioisostere.

PURPOSE A group of 3,4-diaryl- 2(5H)furanones were synthesized to determine whether a N-acetylsulfonamido (SO2NHCOCH3) moiety could be used as a bioisosteric replacement for the traditional sulfonamide (SO2NH2) and methanesulfonyl (SO2CH3) COX-2 pharmacophores. METHODS In vitro COX-1 and COX-2 isozyme inhibition studies were carried out to acquire structure activity relationship data with respect to the point of attachment of the Nacetylsulfonamide moiety at the para and metapositions of the C-4 phenyl ring in conjunction with a variety of substituents (H, F, Cl, Me, OMe) at the para position of the C-3 phenyl ring. RESULTS COX-1 and COX-2 inhibition studies showed that all compounds were selective inhibitors of COX-2 since no inhibition of COX-1 was observed at a concentration of 100 microM. The relative COX-2 potency, and COX-2 selectivity index, profiles for the C-4 para acetamidophenyl compounds, with respect to the C-3 phenyl parasubstituent was H > F > Cl. The point of attachment of the SO2NHCOCH3 substituent on the C-4 phenyl ring was a determinant of COX-2 potency, and COX-2 selectivity, where the relative activity profile was para acetylsulfonamido > meta acetylsulfonamido. 4-[4-(NAcetylsulfonamido) phenyl]-3-phenyl-2(5H)furanone was identified as a more potent (IC50 = 0.32 microM), and selective (S.I. > 313), COX-2 inhibitor than the parent reference compound rofecoxib (IC50 = 0.43 microM, S.I. > 232). CONCLUSIONS The SO2NHCOCH3 moiety i) is a novel COX-2 pharmacophore that also has the potential to serve as a prodrug moiety to the traditional SO2NH2 COX-2 pharmacophore, and ii) it could serve as a useful COX-2 pharmacophore to study the structure-function relationship of the COX-2 isozyme in view of its potential to acetylate the NH2 moiety of amino acid residues such as Gln192 or Arg513 that line the pocket of the secondary COX-2 binding site.