Reaction Steps
Boron trifluoride diethyl etherate (74.0 μL, 0.636 mmol, 0.219 equiv) was added to a solution of glycal 218 (1.020 g, 2.904 mmol, 1.000 equiv) and iodobenzene diacetate (1.119 g, 3.474 mmol, 1.196 equiv) in dichloromethane (36 mL) in a cold bath at −50° C. After 25 min, the yellow solution was transferred to a cold bath at −25° C. and stirred for an additional 30 min. Triethyl amine (2.0 mL) was added, and the resulting suspension was diluted with dichloromethane (20 mL) and washed with saturated aqueous sodium bicarbonate solution (30 mL). The aqueous layer was extracted with dichloromethane (30 mL), and the combined organic layers were dried with magnesium sulfate and purified by silica gel chromatography (hexane/ethyl acetate 4:1 to 3:1) to afford 222 (1.163 g, 2.477 mmol, 85% yield) as a yellow solid. Rf=0.25 (hexane/ethyl acetate 3:1); 1H NMR (400 MHz, CDCl3) δ 7.41-7.28 (m, 10H), 5.51 (d, J=8.3, 1H), 5.30 (dd, J=9.8, 8.4, 1H), 4.74 (d, J=12.2, 1H), 4.56 (d, J=12.3, 1H), 4.54 (s, 2H), 4.08 (dd, J=3.6, 1.1, 1H), 3.74 (td, J=6.7, 1.3, 1H), 3.69 (dd, J=9.8, 3.6, 1H), 3.63 (d, J=6.8, 2H), 2.06 (s, 3H), 2.00 (s, 3H); 13C NMR (126 MHz, CDCl3) δ 169.50, 169.38, 137.51, 137.25, 128.73, 128.69, 128.32, 128.23, 128.20, 127.92, 92.47, 78.73, 73.86, 72.60, 72.23, 69.78, 67.82, 59.10, 20.96, 20.88; FTIR (neat film) 2920.8, 2107.7, 1755.9, 1454.8, 1368.4, 1232.5, 1214.6, 1059.1, 739.3, 698.4 cm−1; HRMS (ESI) m/z: Calcd for C24H27N3O7Na (M+Na+) 492.1747. found 492.1755.
