Reaction Steps
Boron trifluoride etherate (1.30 μL, 0.010 mmol) was added to 23c (13.0 mg, 0.034 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 (83.0 mg, 0.23 mmol) in anhydrous CH2Cl2 (1.30 mL). After stirring at room temperature for 1.5 hours, triethylamine (150 μL) was added and the solvent was concentrated. The residue was purified via column chromatography (SiO2, 40:1 CH2Cl2:Acetone) to give 25c as a colorless foam (19.0 mg, 95%): 1H NMR (CDCl3, 500 MHz) 8.17 (s, 1H), 7.51 (s, 1H), 7.35 (s, 1H), 7.34-7.33 (m, 4H), 6.74 (s, 1H), 5.54 (dd, J=9.2, 1.2 Hz, 1H), 5.16 (s, 2H), 4.87-4.84 (m, 1H), 4.73 (dd, J=7.9, 1.9 Hz, 1H), 4.51 (quintet, J=6.0 Hz, 1H), 3.52 (s, 3H), 3.28 (d, J=4.8 Hz, 1H), 2.33 (s, 3H), 1.80-1.77 (m, 6H), 1.30 (s, 3H), 1.27 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 161.6, 158.6, 153.2 153.1, 147.1, 146.8, 142.5, 135.5, 128.7, 128.6, 128.3, 123.3, 121.4, 121.1, 116.2, 108.6, 99.4, 83.1, 79.9, 76.1, 74.7, 72.2, 68.0, 60.5, 27.1, 25.6, 21.9, 21.6, 21.0, 10.1; IR (film) νmax 2955, 2922, 2853, 2359, 2339, 1819, 1711, 1520, 1464, 1375, 1171, 1111, 1034, 962, 822, 766 cm−1; HRMS (ESI+) m/z: [M+H]+ calcd for C30H33NO11, 584.2132. found, 584.2111.
