Dimethylformamide → N-(2-fluorophenethyl)-2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydropurin-7-yl)acetamide

Compound 101 (600 mg, 2.5 mmol) was mixed with HATU (1.14 g, 3.0 mmol) in 20 mL of DMF under N2 and stirred at room temperature for 20 min. Compound 117 (0.33 mL, 2.5 mmol) was added. The resulting mixture was stirred overnight. EtOAc (100 mL) was added and the resulting solution was washed with water (3×80 mL) and brine (80 mL), dried over Na2SO4 and filtered. The filtrate was concentrated in vacuo and the resulting solid residue was purified by flash column chromatography on 40 g of silica gel eluting with EtOAc/hexanes. The purified product was triturated with ether (30 mL) and filtered to yield 404 as a white solid (281 mg, 31%). MS (APCI): m/z 360 [M+H]+. Anal. Calcd for C17H18FN5O3.0.3H2O: C, 55.98; H, 5.14; N, 19.20. Found: C, 55.87; H, 5.07; N, 19.13.