Reaction Steps
Boron trifluoride etherate (17.3 μL, 0.14 mmol) was added to 23g (157 mg, 0.46 mmol) and (3aR,4S,7R,7aR)-7-methoxy-6,6-dimethyl-2-oxo-tetrahydro-3aH-[1.3]dioxolo[4,5-c]pyran-4-yl 2,2,2-trichloroacetimidate (665 mg, 1.83 mmol) in anhydrous CH2Cl2 (11.5 mL). After stirring at room temperature for 24 hours, triethylamine (150 μL) was added and the solvent was concentrated. The residue was purified via column chromatography (SiO2, 40:1→10:1 CH2Cl2:Acetone) to give 25g as a colorless foam (237 mg, 95%): 1H NMR (CDCl3, 500 MHz) 8.20 (s, 1H), 7.48 (s, 1H), 7.33-7.29 (m, 5H), 7.09 (dd, J=14.2, 8.8 Hz, 2H), 5.72 (d, J=1.8 Hz, 1H), 5.16 (s, 2H), 5.02 (dd, J=7.8, 1.8 Hz, 1H), 4.89 (t, J=7.8 Hz, 1H), 3.88 (s, 3H), 3.52 (s, 3H), 3.21 (d, J=7.8 Hz, 1H), 1.27 (s, 3H) 1.17 (s, 3H); 13C NMR (CDCl3, 125 MHz) 158.0, 153.3, 153.2, 153.1, 149.8, 143.8, 137.1, 135.5, 128.7 (2C), 128.6, 128.3 (2C), 122.7, 122.2, 121.4, 116.1, 113.7, 95.3, 74.7, 72.9, 67.6, 61.9, 60.7, 60.6, 29.7, 29.4; IR (film) νmax 3400, 3319, 2984, 2935, 2359, 1815, 1715, 1609, 1526, 1464, 1383, 1364, 1285, 1213, 1175, 1111, 1063, 968, 764, 737, 700 cm−1; HRMS (ESI+) m/z: [M+Na]+ calcd for C27H27NO11, 564.1482; found, 564.1455.
