Reaction Steps
Potassium carbonate (0.600 g, 4.34 mmol, 3.99 equiv) was added to a solution of diacetate 222 (0.511 g, 1.09 mmol, 1.00 equiv) in methanol (50 mL) and water (5 mL). After 1.5 h, the yellow solution was decanted from the undissolved potassium carbonate and concentrated to about 4 mL and then diluted with dichloromethane (50 mL) and washed with saturated aqueous sodium bicarbonate solution (10 mL). The aqueous layer was extracted with dichloromethane (2×10 mL) and the combined organic layers were dried with magnesium sulfate and purified by silica gel chromatography (ethyl acetate) to afford 223 (0.353 g, 0.917 mmol, 84% yield) as a yellow oil (1:1 α:β). Rf=0.17, 014 (hexane/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3) δ 7.43-7.27 (m, 20H), 5.28 (d, J=3.8, 1H), 4.78 (d, J=11.5, 1H), 4.78 (d, J=11.5, 1H), 4.67 (d, J=11.5, 1H), 4.68 (d, J=11.5, 1H), 4.58 (d, J=11.9, 1H), 4.56 (d, J=11.9, 1H), 4.52 (d, J=11.9, 1H), 4.51 (d, J=11.9, 1H), 4.51 (d, J=7.7, 1H), 4.21 (td, J=6.5, 1.1, 1H), 4.02 (dd, J=3.4, 1.3, 1H), 3.99 (dd, J=9.9, 3.8, 2H), 3.85 (dd, J=9.7, 3.5, 1H), 3.73 (dd, J=9.5, 7.7, 1H), 3.69-3.51 (m, 6H); 13C NMR (126 MHz, CDCl3) δ 137.62, 137.50, 137.48, 128.67, 128.59, 128.16, 128.13, 128.10, 128.09, 128.07, 128.02, 128.00, 97.08, 92.50, 80.85, 78.06, 73.64, 73.61, 72.63, 72.51, 72.14, 71.82, 69.25, 68.76, 68.68, 67.38, 60.27, 59.49; FTIR (neat film) 3401.3, 3032.4, 2921.6, 2105.6, 1454.4, 1367.2, 1279.3, 1095.8, 1028.3, 738.1, 698.0 cm−1; HRMS (ESI) m/z: Calcd for C20H23N3O5Na (M+Na+) 408.1535, found 408.1535.
