Reaction Steps
Benzyl bromide (0.236 g, 1.38 mmol) and K2CO3 (0.190 g, 1.38 mmol) were added to a stirred solution of 43 (0.400 g, 1.15 mmol) in anhydrous DMF (7 ml) under Ar. The reaction mixture was stirred at room temperature overnight and the mixture was poured in water (15 ml). The product was extracted with ethyl acetate (2×15 ml), dried over Na2SO4 and the solvent removed under reduced pressure. The resultant product 44 was stirred in the microwave reactor in presence of DBU (0.192 g, 1.27 mmol), and nitromethane (7 ml) in the microwave), at 100° C. for 15 min. After cooling to room temperature, the reaction mixture was poured into HCl 1M (10 ml). The product was extracted with ethyl acetate (2×15 ml), dried over Na2SO4 and the solvent removed under reduced pressure. Chromatography on silica gel (60:40 hexanes/ethyl acetate) afforded 49 (0.413 g, 0.83 mmol, 72%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 2.88 (1H, dd, J 6.8, 15.6 Hz), 2.96 (1H, dd, J 7.2, 15.2 Hz), 3.86 (3H, s), 4.26 (1H, quint, J 7.1 Hz), 4.83 (1H, dd, J 7.4, 12.6 Hz), 4.93 (1H, dd, J 6.8, 12.4 Hz), 5.10 (2H, s), 6.71 (1H, dd, J 2.0, 8.8 Hz), 7.13 (1H, bs), 7.28-7.32 (1H, m), 7.36-7.39 (3H, m), 7.47-7.52 (5H, m), 7.71 (1H, bs), 7.77-7.86 (4H, m). 13C NMR (400 MHz, CDCl3) δ 40.68, 40.81, 52.15, 70.70, 79.44, 101.39, 111.15, 115.91, 124.94, 126.67, 126.79, 126.89, 127.22, 127.93, 128.05, 128.79, 128.72, 129.39, 133.11, 133.60, 135.89, 136.54, 142.68, 159.61, 166.42, 168.57. MS (API-ES): m/z found 499 [M+H]+ (100%), HRMS (API-ES) m/z 499.1862 [M+H]+.
