To a solution of 500 g of the compound (CAS:1207284-89-6) in 4.25 L of N-methylpyrrolidone was added N,N-diisopropylethylamine (620 mL), followed by benzyl bromide (425 mL, 2.5 equiv). The reaction mixture was heated at 100 °C for 18 h, after which it was cooled to 80 °C and treated with 25% w/w aqueous triethylamine solution for 10 min. The mixture was stirred at room temperature for 25 minutes and subsequently cooled to 15 °C and water (10 L) was added to precipitate the product. After 3 h of precipitation, the resulting light-colored suspension was filtered and washed with 2 L of water and subsequently dried. The crude product (750 g) was dissolved in 4.1 L of toluene and filtered through silica gel to give 762 g of yellow solid. This solid was recrystallized by acetone/heptane to give a final 606 g of the target compound 2-(benzyloxy)-3-(benzylamino)-5-fluoro-6-methylbenzoic acid (80% yield) as a white solid. Its 1H NMR (400 MHz, CDCl3) data were as follows: δ 7.48-7.03 (m, 20H), 6.60 (d, J=11.5 Hz, 1H), 5.31 (s, 2H), 4.33 (s, 4H), 2.30 (s, 3H).
