Thionyl chloride (308 μl, 502 mg, 4.22 mmol) was added to 4-methoxy-3-(3-methoxyphenyl)-benzoic acid (365 mg, 1.41 mmol) in anhydrous THF (4.75 mL) at room temperature, and the resulting solution was heated at reflux for 4.5 hours. The solvent was removed and the resulting acid chloride was used without further purification. Sodium hydride (85 mg, 2.12 mmol) was added to 37 (378 mg, 1.02 mmol) in anhydrous THF (7.50 mL). After stirring for two hours at room temperature, a solution of the freshly-prepared acid chloride (1.41 mmol) in anhydrous THF (2.40 mL) was added and the reaction was heated to reflux for 18 hours. The reaction was cooled, partitioned between saturated aqueous NaHCO3 (50 mL) and CH2Cl2 (50 mL), then extracted with CH2Cl2 (3×100 mL). Combined organic extracts were washed with saturated aqueous NaCl solution (200 mL), dried (Na2SO4), filtered, and concentrated. The residue was purified via column chromatography (SiO2, 4:1:1 Hexanes:EtOAc:CH2Cl2) to give 38 as a brown-yellow amorphous solid (515 mg, 83%): 1H NMR (CDCl3, 500 MHz) δ 7.58 (d, J=9.0 Hz, 1H), 7.55 (d, J=8.7 Hz, 1H), 7.50-7.45 (m, 3H), 7.44-7.40 (m, 2H), 7.38-7.34 (m, 2H), 7.29 (d, J=2.2 Hz, 1H), 7.25 (m, 2H), 7.21 (dd, J=8.9, 2.6 Hz, 1H), 7.15 (d, J=2.4 Hz, 1H), 7.09 (m, 1H), 7.01 (dd, J=8.7, 2.1 Hz, 1H), 6.80 (m, 2H), 6.77 (ddd, J=8.2, 2.7, 0.9 Hz, 1H), 6.74 (d, J=8.7 Hz, 1H), 6.59-6.56 (m, 2H), 5.16 (s, 2H), 5.14 (s, 2H), 3.78 (s, 3H), 3.72 (s, 3H), 3.62 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 170.0, 159.3, 159.0, 157.6, 157.3, 139.9, 139.1, 136.8, 133.0, 132.4, 130.5, 130.1, 130.1 (2C), 129.6, 129.5, 129.1, 128.9, 128.9 (2C), 128.4, 128.2, 127.9, 127.7 (2C), 127.3, 125.8, 122.1, 120.0, 114.7, 114.0 (2C), 113.2, 110.4, 107.1, 70.3, 55.7, 55.4, 55.2, 53.9; IR (film) νmax 3059, 3032, 2999, 2934, 2835, 1636, 1601, 1506, 1456, 1389, 1248, 1209, 1026, 854, 818, 735, 698 cm−1; HRMS (ESI+) m/z: [M+H]+ calcd for C40H35NO5, 610.2593; found, 610.2567.
