General procedure for the synthesis of 4-[[(3-phenoxyphenyl)methyl]amino]phenylacetic acid from 3-(4-aminophenyl)propionic acid and m-phenoxybenzaldehyde: To a solution of 3-phenoxybenzaldehyde (3.2 mL, 18.5 mmol) in dichloroethane (60 mL) was added 3-(4-aminophenyl)propionic acid (3.0 g, 18.5 mmol). The mixture was sonicated and subsequently transferred to a 20 mL microwave reaction flask. The reaction was carried out in a microwave reactor at 100 °C for 10 min. After completion of the reaction, the solution was transferred to a 500 mL round bottom flask and sodium triacetoxyborohydride (7.8 g, 36.9 mmol) was added in batches. The reaction mixture was stirred at room temperature for 1 hour. Water (100 mL) was added to the reaction mixture and the organic layer was separated. The organic layer was washed twice sequentially with water (100 mL) and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure and the crude product was purified by silica gel column chromatography with the eluent being a solvent mixture of hexane/ethyl acetate in the ratio of 1:1, v/v, with the addition of a trace amount of acetic acid. Pure 3-(4-((3-phenoxybenzyl)amino)phenyl)propanoic acid (5.5 g, 86% yield) was finally obtained as a low melting point solid. The product was confirmed by 1H NMR (CDCl3) and mass spectrometry (MS): 1H NMR (CDCl3) δ 2.40 (t, 2H), 2.63 (t, 2H), 4.21 (s, 2H), 6.09 (bs, 1H), 6.44-6.47 (m, 2H), 6.81-6.83 (m, 1H), 6.87-6.89 (m, 2H) , 6.94-6.97 (m, 2H), 7.07 (bs, 1H), 7.11-7.18 (m, 2H), 7.29-7.33 (m, 1H), 7.35-7.38 (m, 2H), 12.09 (bs, 1H); MS m/z = 348 (M + H+).
