Reaction Steps
A solution of KOH (110 mg, 2.0 mmol) in EtOH (3 mL) was added at 0° C. to a stirred solution of 4 (2.52 g, 7.9 mmol) and methyl vinyl ketone (0.61 g, 8.7 mmol) in THF (60 mL). The resulting mixture was stirred at room temperature overnight. Ether (200 mL) and HCl (50 mL, 10% aqueous solution) were added. The organic phase was washed with HCl (50 mL, 10% aqueous solution), H2O (50 mL), NaHCO3 (50 mL, saturated aqueous solution), dried over Na2SO4 and evaporated under reduced pressure. The crude material was dissolved in EtOH (40 mL) and HCl (2 mL, 37% aqueous solution) was added. The mixture was heated at 50° C. for 30 min under stirring. After cooling to room temperature, H2O (50 mL) was added. The mixture was extracted with diethyl ether (3×100 mL) and the combined organic phase was washed with NaHCO3 (2×50 mL, saturated aqueous solution) and brine (50 mL), dried over Na2SO4 and evaporated under reduced pressure to yield 2.89 g crude material. Purification by column chromatography (heptane:ethyl acetate 4:1 to 2:1) yielded 2.41 g, 82% as an off-white solid. 1H-NMR (CDCl3) δ; 7.44-7.35 (m, 6H), 7.35-7.28 (m, 2H), 7.17 (dt, 1H, J=7.5 Hz and 1.4 Hz), 7.11 (d, 2H, J=8.9 Hz), 7.02 (dd, 1H, J=7.0 Hz and 1.4 Hz), 6.92 (d, 2H, J=8.9 Hz), 6.19 (d, 1H, J=10.3 Hz), 5.04 (s, 2H), 2.90-2.81 (m, 1H), 2.62-2.52 (m, 1H), 2.44 (at, 2H, J=6.6 Hz); 13C-NMR (CDCl3) δ; 199.0, 161.3 (d, J=249.6 Hz), 157.9, 154.9 (d, J=3.8 Hz), 137.1 (d, J=12.1 Hz), 132.0 (d, J=10.8 Hz), 129.5 (d, J=8.8 Hz), 129.3, 128.8, 128.7 (d, J=4.2 Hz), 128.2, 128.1, 127.7, 124.3 (d, J=3.5 Hz), 117.2 (d, J=22.7), 115.0, 70.3, 47.3 (d, J=1.9 Hz), 35.1, 35.0;
