Reaction Steps
To an ice-cooled solution of 21 (125 mg, 0.126 mmol, 1 eq.) in dichloromethane, a 1 M solution of boron trichloride in dichloromethane (320 μL, 0.32 mmol, 2.5 eq) was added dropwise while stirring. The mixture was allowed to stand at 0° C. for 15 min and then was poured into the ice-cold water. The aqueous layer was extracted. with dichloromethane (3×50 mL). The combined organic extracts were dried over anhydrous magnesium sulfate, filtered and evaporated under reduced pressure. The crude reaction mixture was purified by flash column chromatography to give 78 mg of product mixture of meso-22 and (±)-22 as a white solid (75% combined yield). The mixture of meso-22 and (±)-22 was further purified on silica gel column using gradient of EtOAC in dichloromethane from 10% to 50% in order to separate meso-22 and (±)-22. Analytical data for (±)-22: 1H NMR (CDCl3, ppm) δ: 7.32 (d, 4H), 6.93 (d, 4H) 6.89 (d, 4H), 6.86 (d, 4H), 5.08 (s, 2H), 4.47 (dd, J=6 Hz, 13 Hz, 2H), 4.37 (d, 2H), 4.26 (m, 2H), 3.98 (dd, J 10 Hz, 13 Hz, 2H), 3.80 (s, 6H), 3.41 (s, 6H), 2.98 (d, 2H), 2.84 (s, 6H), 2.69 (d, 2H). 13C NMR (DMSO-d6, ppm) δ:165.42, 165.19, 160.06, 140.00, 132.93, 130.52, 128.53, 128.42, 126.82, 114.38, 73.47, 71.51, 60.79, 55.29, 49.91, 40.14, 36.36, 29.60, 27.96. FABMS: Calcd. for C46H50N4O8S4: 914.3. Found [M+Na]+: 936.9. Analytical data for meso-7: 1H NMR (CDCl3, ppm) δ: 7.33 (d, 4H), 7.02 (d, 4H) 6.99 (d, 4H), 6.86 (d, 4H), 5.09 (s, 2H), 4.35 (dd, J=10 Hz, 13 Hz, 2H), 4.37 (d, 2H), 3.11 (m, 2H), 4.04 (dd, J=10 Hz, 13 Hz, 2H), 3.81 (s, 6H), 3.41 (s, 6H), 2.91 (s, 6H), 2.85 (s, 4H). 13C NMR (DMSO-d6, ppm) δ:165.47, 165.24, 160.10, 140.04, 132.96, 130.56, 128.55, 128.48, 126.85, 114.42, 73.50, 71.55, 60.83, 55.34, 49.96, 40.14, 36.42, 29.63, 28.00. FABMS: Calcd. for C46H50N4O8S4: 914.3. Found [M+Na]+: 936.9.
