To a stirred solution at room temperature of VII (264 mg, 1.28 mmol) in anhydrous DMF (10 ml) under nitrogen were added Et3N (196 μl, 1.41 mmol) and BOP reagent (680 mg, 1.1.54 mmol), respectively. After few min, a precipitate appeared. After 3 h, the reaction mixture was poured into a saturated aqueous solution of NH4Cl, and diluted with AcOEt. After separation, the organic layer was successively washed with sat NH4Cl, H2O and brine, concentrated a little bit, and hexane was added. The suspension was filtered off and rinsed with hexane. The solid was triturated in water, filtered off, rinsed with water, and dried to afford the title compound VIII (346 mg, 1.07 mmol, 84% yield) as a pale yellow solid (not stable on silica gel !). 1H NMR (300 MHz, CDCl3) δ(ppm): 8.56 (d, J=8.3 Hz, 1H), 8.21–8.02 (m, 3H), 7.90–7.72 (m, 4H), 7.62 (t, J=7.4 Hz, 1H), 3.97 (s, 3H).
