Reaction Steps
Sodium hydride (60%, 4.69 g, 0.117 mol) was added in portions to 18 (5.47 g, 35.5 mmol) in DMF (150 mL) with ice bath cooling, and the mixture was stirred at 0° C. for 45 min and at room temperature for 1 h. A solution of 4-methoxybenzyl bromide (25.0 g, 0.124 mol) in DMF (50 mL) was added to the reaction mixture over 30 min. After stirring for 20 h, quenching with H2O (30 mL) at 0° C. was performed, and solvents were removed under high vacuum. The concentrate was dissolved in EtOAc (200 mL), which was washed with H2O (100 mL) and saturated NaCl (100 mL); solvent was removed in vacuo. Flash chromatography, eluting with 5:1 hexanes/EtOAc, gave 11.33 g (62%) of 19 as a white solid, mp 108° C.: 1H NMR δ 3.77 (s, 3H), 3.79 (s, 3H), 3.81 (s, 3H), 4.95 (s, 2H), 5.03 (s, 2H), 5.25 (s, 2H), 6.76 (d, 2H, J=8.8), 6.86 (d, 2H, J=8.8), 6.89 (d, 2H, J=8.4), 7.04 (t, 2H, J=7.8), 7.11 (dd, 2H, J=8.0, 2.0), 7.18 (d, 2H, J=8.8), 7.33-7.36 (m, 4H); 13C NMR δ 55.32, 55.37, 55.40, 66.81, 71.20, 75.31, 112.97, 113.61, 114.02, 118.16, 123.93, 127.08, 128.19, 128.75, 129.51, 129.73, 130.31, 130.41, 148.43, 152.95, 159.43, 159.62, 159.70, 166.44; HRMS m/z calcd for C31H30NaO7, 537.1889 (M+Na). found, 537.1884.
