N-Hydroxyphthalimide (2.06 g, 12.7 mmol) and triethylamine (2.40 mL, 17.3 mmol) were added to a solution of tert-butyl 3-[2-(chloromethyl)-1H-imidazo[4,5-c][1,5]naphthyridin-1-yl]propylcarbamate (prepared as described in Parts A-D of Example 92, 11.5 mmol) in DMF (60 mL). The reaction was allowed to stir overnight at room temperature. The resulting orange suspension was diluted with water (40 mL) and the solid was isolated by filtration, washed with water (2×30 mL), and dried in a vacuum oven at 70° C. to afford 4.86 g of tert-butyl 3-(2-{[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)oxy]methyl}-1H-imidazo[4,5-c][1,5]naphthyridin-1-yl)propylcarbamate as a white solid. The material was used without further purification in the next step.
