To a solution of 2-(4-(dimethylamino)phenyl)-1-phenylethanone (Intermediate 44) (235 mg, 1 mmol), 3-ethoxy-4-hydroxy-5-nitrobenzaldehyde (212 mg, 1 mmol), and urea (138 mg, 3 mmol) in 10 mL of ethanol was added 0.2 mL of concentrated HCl solution, and the mixture was stirred at 130° C. for 2 days. After the solvent was removed under reduced pressure, the residue was purified by preparative HPLC (40-80% acetonitrile+0.1% trifluoroacetic acid in water, over 15 min.) to give the Compound 88 (65 mg, yield 13.9%). 1H NMR (CD3OD 400 MHz): δ 7.43 (s, 1H), 7.25-7.19 (m, 8H), 7.02 (d, J=8.4 Hz, 2H), 5.30 (s, 1H), 4.06-4.00 (m, 2H), 3.06 (s, 6H), 1.33 (t, J=6.8 Hz, 3H); MS (ESI): m/z 475.3 [M+1]+.
