A mixture of N-(4-methoxybenzyl)-4-nitropyridin-2-amine 1-oxide (25.6 g, 0.0929 mol), 7-hydroxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic acid (17 g, 0.088 mol) and cesium carbonate (92 g, 0.28 mol) in DMF (200 mL, 3 mol) was heated with stirring at 80° C. overnight. The reaction mixture was allowed to cool and then concentrated to small volume and 200 ml of water was added. The solution was acidified with conc. HCl to pH=4. The aqueous solution was removed and the remaining organic solution was washed with water (3×). The residue was treated with 1N NaOH (150 ml) and extracted with DCM (3×). The aqueous solution was acidified with conc. HCl. A precipitate formed and was filtered, washed with water (3×), and dried to give 7-({2-[(4-methoxybenzyl)amino]-1-oxidopyridin-4-yl}oxy)-1,2,3,4-tetrahydronaphthalene-2-carboxylic acid (33 g, 89%) as a brown solid. 1H NMR (d6-DMSO, 400 MHz) δ: 12.40 (s, 1H); 8.03 (d, 1H); 7.80 (t, 1H); 7.20 (d, 2H); 7.12 (d, 1H); 6.82 (d, 2H); 6.76 (m, 2H); 6.20 (s, 1H); 6.10 (d, 1H); 4.30 (d, 1H); 3.70 (s, 3H); 2.80 (m, 4H); 2.65 (m, 1H); 2.08 (m, 1H); 1.74 (m, 1H) LCMS ES+ 421.1
