Reaction Steps
A stirred solution of 5.07 (9.2 g, 15 mmol) in ethyl ether (250 mL) was chilled to −78° C. then methyl lithium (48 mL of 1.6 M solution in diethyl ether, 76 mmol) was added dropwise over 20 minutes. The reaction was kept at −78° C. for an additional 4 h then warmed to room temperature and carefully quenched with saturated NH4Cl and transferred to a separatory funnel containing diethyl ether. The organic phase collected then washed with H2O and brine, dried over over Na2SO4, decanted, and concentrated in vacuo. The resulting oil was purified by silica gel chromatography (8-12% EtOAc/petroleum ether) to give the desired glucopyranoside product 5.08 (7.2 g, 11.6 mmol, 76%) and its galactopyranoside diastereomer (2.1 g, 3.4 mmol, 22%). Desired glucopyranoside product 5.08: 1H NMR (500 MHz, CDCl3): δ ppm 7.38-7.27 (m, 7H, ArH), 6.86 (d, J=8.8 Hz, 2H, PMPH), 4.89, 4,71 (ABq, J=10.7 Hz, 1H each, OCH2Ar), 4.84, 4.79 (ABq, J=11.0 Hz, 1H each, OCH2Ar), 4.44 (d, J=7.8 Hz, 1H, H-1), 4.04-3.97 (m, 1H, OCHHCH2SiMe3), 3.92-3.81 (m, 2H, H-6), 3.80 (s, 3H, OMe), 3.57-3.65 (m, 1H, OCHHCH2SiMe3), 3.49 (d, J=9.8 Hz, 1H, H-3), 3.42 (t, J=6.8 Hz, 1H, H-5), 3.27 (dd, J=9.8, 7.8 Hz, 1H, H-2), 1.30 (s, 3H, Me2), 1.05 (t, J=8.3 Hz, 2H, OCH2CH2SiMe3), 0.93 (s, 9H, SiCMe3), 0.13, 0.12 (s, 3H each, SiMe), 0.04 (s, 9H, SiMe3); 13C NMR (125 MHz, CDCl3): δ ppm 159.21, 138.96, 131.46, 129.60, 128.41, 128.14, 127.66, 113.85, 103.85, 86.30, 81.41, 75.78, 75.32, 75.16, 75.10, 67.85, 62.73, 55.36, 25.99, 18.71, 18.31, 16.37, −1.29, −5.32, −5.48; HRMS calcd for C33H58NO7Si2 [M+NH4]+: 636.3752. found 636.3726.
