Reaction Steps
Boron trifluoride etherate (19.0 μL, 0.15 mmol) was added to 23h (171 mg, 0.51 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 (183 mg, 0.51 mmol) in anhydrous CH2Cl2 (11.0 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 CH2Cl2:Acetone) to give 25h as a colorless foam (138 mg, 51%): 1H NMR (CD2Cl2, 400 MHz) 8.29 (s, 1H), 7.62 (s, 1H), 7.47-7.38 (m, 5H), 7.36 (d, J=8.8 Hz, 1H), 7.19 (d, J=8.4 Hz, 1H), 5.81 (d, J=2.4 Hz, 1H), 5.25 (s, 2H), 5.10 (dd, J=8.0, 2.0 Hz, 1H), 5.02 (t, J=7.8 Hz, 1H), 3.55 (s, 3H), 3.41 (d, J=7.2 Hz, 1H), 2.87 (q, J=7.4 Hz, 2H), 1.42 (s, 3H), 1.28 (s, 3H), 1.21 (t, J=7.4 Hz, 3H); 13C NMR (CD2Cl2, 100 MHz) 158.5, 154.8, 153.2, 153.1, 148.4, 136.0, 128.6 (2C), 128.4, 128.1, 125.6, 122.4, 121.5, 120.7, 114.8, 111.4, 94.8, 82.7, 77.9, 77.2, 76.6, 67.3, 60.3, 27.3, 22.3, 16.4, 13.6; IR (film) νmax 3400, 2980, 2937, 2359, 2339, 1817, 1711, 1607, 1524, 1383, 1366, 1227, 1205, 1175, 1101, 1040, 906, 768, 737, 700 cm−1; [M+Na]+ calcd for C28H29NO10, 562.1689. found, 562.1689.
