To a 25 mL round-bottom flask equipped with a magnetic stir bar was added 2-(4-fluoro-2-methyl-phenylamino)-7-(1-hydroxy-allyl)-1,6-dimethyl-1,8-dihydro-imidazo[4,5-h]isoquinolin-9-one (0.65 g, 1.7 mmol), THF (5 mL), triethylamine (0.52 g, 5.1 mmol) and acetic anhydride (0.22 g, 2.2 mmol). To the stirred suspension was then added DMAP (0.002 g, 0.02 mmol). After 1 hour, all reaction components were fully dissolved and the reaction was complete as determined by TLC analysis. To the reaction mixture was added saturated aqueous ammonium chloride (20 mL) and the solution was extracted with ethyl acetate (2×20 mL). The organic fractions were collected, washed with brine (1×20 mL), dried over sodium sulfate, and concentrated in vacuo. The crude product was further purified by silica gel chromatography, eluting with 2% methanol:DCM to provide acetic acid 1-[2-(4-fluoro-2-methyl-phenylamino)-1,6-dimethyl-9-oxo-8,9-dihydro-1H-imidazo[4,5-h]isoquinolin-7-yl]-allyl ester (0.404 g, 55%) as a yellow solid. 1H NMR (400 MHz, DMSO-d6+TFA) δ ppm 11.35 (br s, 1H), 10.55 (br s, 1H), 7.74 (d, 1H, J=9.0 Hz), 7.70 (d, 1H, J=8.6 Hz), 7.56 (dd, 1H, J1=5.5 Hz, J2=8.6 Hz), 7.37-7.34 (m, 3H), 7.25 (td, 1H, J1=2.7 Hz, J2=8.2 Hz), 6.34 (app d, 1H, J=6.3 Hz), 6.17 (ddd, 1H, J1=6.3 Hz, J2=10.2 Hz, J3=16.8 Hz), 5.41 (app d, 1H, J=17.2 Hz), 5.33 (app d, 1H, J=10.2 Hz), 4.18 (s, 3H), 2.32 (s, 3H), 2.12 (s, 3H); ESMS (m/z): found, 435.
