Reaction Steps
Acid 5a (0.583 g., 1.90 mmol, 1 equiv.) is dissolved in 12 mL of absolute EtOH. Concentrated HCl (0.6 mL) is added, and the mixture heated to reflux for 24 hours. The mixture is then partitioned between EtOAc and water. The organic phase is washed with brine, dried (MgSO4), and concentrated in vacuo. Chromatography on silica gel using 5%, then 10% EtOAc/hexane yields 2-methoxy-3'-carboethoxy-[1,1'-biphenyl]-6-carboxylic acid, ethyl ester (6a) (0.432 g., 1.32 mmol, 73%) as a clear oil: UVmax (CHCl3) 242 nm (ε=12036), 296 nm (ε=4724); 1H NMR (300 MHz, CDCl3) δ 8.01 (m, 1H, ArH), 7.92 (m, 1H, ArH), 7.47-7.40 (m, 3H, ArH), 7.39 (dd, J=8, 8 Hz, 1H, ArH), 7.09 (dd, J= 2, 8 Hz, 1H, ArH), 4.34 (q, J=7 Hz, 2H, CO2CH2), 3.98 (q, J=7 Hz, 2H, CO2CH2), 3.73 (s, 3H, OCH3), 1.35 (t, J=7 Hz, 3H, CH2CH3), 0.91 (t, J=7 Hz, 3H, CH2CH3); 13C NMR (75 MHz, CDCl3) δ 168.04 (C=O), 166.65 (C=O), 156.92, 137.28, 134.11, 133.22, 130.73, 130.07, 129.98, 128.78, 128.22, 127.63, 121.63, 113.87, 60.88, 56.02, 14.34, 13.65; IR (film) 2982, 1718, 1466, 1366, 1298, 1260, 1234, 1110, 1060 cm-1 ; MS (DCI) m/e 329 (MH+), 283 (M--C2H5O). Anal. Calcd for C19H20O5 : C, 69.50; H, 6.14. Found: C, 69.44; H, 6.19.
