(Boc)2O (6.9 g, 31.65 mmol) was added at room temperature to a solution of 7.3 (10 g, 21.1 mmol), vinyl bromide (230 mL, 1.0 M solution in THF), DMAP (256 mg, 2.1 mmol), and TEA (3.5 mL, 25.3 mmol). The mixture was stirred at room temperature for 2.5 days. During the reaction, more (Boc)2O (2 g twice) was added. After HPLC indicated that all 7.3 was consumed, the reaction mixture was taken into EtOAc (500 mL), and saturated sodium bicarbonate (400 mL) was added. The organic layer was separated, washed with brine, dried, and concentrated under vacuum. The crude product was taken into hot MeOH (70 mL). The mixture was stirred vigorously at 75° C. for 5 hours. The mixture was then cooled to room temperature and allowed to stand for 3 hours. The solid product was collected by filtration and washed with MeOH to give 7.4 (9.5 g). MS ESI (pos.) m/e: 483 (M+H). 1H NMR (CDCl3) δ 8.30 (d, 1H), 7.30 (m, 2H), 6.95 (d, 2H), 6.15 (d, 1H), 5.05 (s, 2H), 4.76 (dd, 1H), 4.64 (m, 1H), 4.15 (d, 2H), 4.05 (dd, 1H), 3.56 (dd, 1H), 3.23 (dd, 1H), 2.78 (dd, 1H).
