Synthesis of N-(chlorophenyl ) -2 -hydroxynicotinanilides as potential anti-inflammatory agents

Leflunomide 1 and its non-enzymically active metabolite, malononitrilamide (MNA, 2) are clinical use for treating rheumatoid arthritis (RA). Study indicated that the active pharmacophore, a β-keto amide with the enolic hydroxyl group, was fully responsible for the immunosuppressive effects of malononitrilamide 2 leading a salicylamide derivative 3 developed. Previously, we have conducted isosterically structural modification mainly based on salicylamide derivative 3, which β-hydroxy-enamide-containing portion remains untouched, to successfully synthesize a series of N-(4-substituted phenyl)-2-hydroxynicotinanilides. After pharmacological screenings, compounds bearing electron-withdrawing groups such as 4-Cl, 4-Br, and 4-NO2 significantly showed potent anti-inflammatory activity. Currently, a series of compounds 5-14, which are the chloro variants on phenyl moiety, mainly based on N-(substituted phenyl)-2-hydroxynicotin-anilide 4-14 were further synthesized in high yields. After systematic pharmacological screenings of compounds 4-14 and controls, compound 14 exhibited potent in-vivo anti-inflammatory activity comparable to that of compound 5 and Leflunomide 1, whereas the other compounds have comparable activity to compound 4 and malononitrilamide 2 by both in vitro suppressing nitric oxide (NO) production under the LPS-elicited macrophage Raw 264.7 cell and the in-vivo carrageenaninduced paw edema assay, except for compounds 8 and 11.