Example 18: (i) To a solution of 3-(2,3-dihydroxypropyl)-5-(2-fluoro-4-iodophenylamino)-8-methylpyrido[2,3-d]pyrimidin-4,7(3H,8H)-dione (Example 6) (1 g, 2.06 mmol, 1 eq.) in DMF (19 mL) was added dropwise under nitrogen protection at ambient temperature a solution of Selectfluor (801 mg, 2.26 mmol, 1.1 eq.) in a mixture of acetonitrile (9 mL) and DMF (5 mL). The reaction mixture was stirred at ambient temperature for 10 minutes and then filtered. The filtrate was purified by preparative LC/MS (30-55% CH3CN/H2O) to afford (R)-3-(2,3-dihydroxypropyl)-6-fluoro-5-(2-fluoro-4-iodophenylamino)-8-methylpyrido[2,3-d]pyrimidine-4,7(3H,8H)-dione (Example 18) as an off-white solid. The recovered feedstock was reacted under the same reaction conditions to give a second batch of product. The total yield was 347 mg (33%).1H NMR (400 MHz, DMSO-J6) δ ppm 3.36-3.40 (m, 1H), 3.43-3.50 (m, 1H), 3.58 (s, 3H), 3.61-3.72 (m, 1H), 3.72-3.82 (m, 1H), 4.27-4.37 (m, 1H) , 4.78-4.87 (m, 1H), 5.14 (d, J = 5.81 Hz, 1H), 6.93-7.03 (m, 1H), 7.53 (d, J = 8.84 Hz, 1H), 7.65-7.74 (m, 1H), 8.52 (s, 1H), 10.25 (d, J = 10.1 Hz, 1H). The calculated value for [M + H] C17H15F2IN4O4 is 505; the measured value is 505.