Reaction Steps
A mixture of commercially available 8-(2-methoxyphenyl)-1-methyl-7-phenyl-1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione (5, 200 mg, 0.516 mmol) in concentrated H2SO4 (0.103 mL) and acetic anhydride (1.29 mL) was refluxed for 2 h. The reaction was cooled to room temperature, poured into 10 mL of water, and extracted with CH2Cl2 (2×10 mL). The organic extracts were dried over MgSO4 and evaporated under reduced pressure. Purification by column chromatography on silica gel using a gradient CH2Cl2:EtOAc from 5:1 to 1:1 afforded the desired compound as a white solid (88 mg, 39% yield). 1H NMR (500 MHz, DMSO-d6): δ=11.03 (s, 1H), 7.54 (d, J=7.9 Hz, 1H), 7.42 (t, J=7.8 Hz, 1H), 7.30-7.37 (m, 5H), 7.08 (d, J=7.9 Hz, 1H), 7.02 (t, J=7.8 Hz, 1H), 3.60 (s, 3H), 3.30 (s, 3H), 2.46 (s, 3H); 13C NMR (100 MHz, DMSO-d6, CDCl3): δ=187.6, 154.4, 153.6, 153.0, 150.6, 146.8, 135.7, 131.4, 130.7, 129.8, 129.6, 127.5, 126.4, 121.2, 120.6, 120.1, 112.5, 101.0, 55.5, 29.6, 28.8; IR (film): ν=3160, 3050, 1668, 1490, 1292, 1211, 1023, 751, 555 cm−1; HRMS (ESI): m/z: calcd for C23H19N5O4Na+: 452.1335, found: 452.1338.
