To methyl 3-[4-[(4-fluoro-2-{[(methoxycarbonyl)amino]methyl}benzyl)oxy]-6-methyl-2-oxopyridin-1(2H)-yl]-4-methylbenzoate (from Step 3) (0.17 g, 0.36 mmol) was added 1.5 N NaOH solution in 1:1 MeOH:water (0.39 mL, 0.59 mmol). The reaction mixture was stirred at 60° C. for 2.5 h. The solution was cooled (0° C.), neutralized by the slow addition of 5% citric acid, and organic products extracted in DCM. A white solid suspended in the organic layer was filtered, washed with DCM and water, dried in vacuo, and found to be the desired product (0.090 g, 55%). 1H NMR (CD3OD/400 MHz) δ8.03 (m, 1H), 7.75 (s, 1H), 7.52 (d, 1H, J=8.0 Hz), 7.47 (m, 1H), 7.12 (m, 1H), 7.03 (m, 1H), 6.21 (s, 1H), 6.08 (s, 1H), 5.18 (s, 2H), 4.38 (s, 2H), 3.65 (s, 3H), 2.12 (s, 3H), 1.90 (s, 3H). ESHRMS m/z 455.1632 (M+H calculated for C24H24FN2O6 requires 455.1613).
