Reaction Steps
A solution of the ester 55 (0.106 g, 0.220 mmol) in methanol (3 ml) and THF (3 ml) was stirred in presence of NaOH (aq, 1M, 1 ml) at room temperature overnight. The solvent was removed under reduced pressure. HCl (aq, 1M, 1.5 ml) was added and the white precipitate was filtered, washed with water (5 ml) and dried under vacuum. Pure 59 was obtained as a white solid (0.085 g, 0.188 mmol, 85%) without further purification, mp 225-227° C. 1H NMR (400 MHz, CD3OD) δ2.39 (3H, s), 2.62 (1H, dd, J 8.4, 14.8 Hz), 2.35 (1H, dd, J 6.6, 14.6 Hz), 3.05 (1H, dd, J 8.0, 13.0 Hz), 3.12 (1H, dd, J 7.2, 12.8 Hz), 7.16-7.19 (3H, m), 7.24-7.27 (2H, m), 7.30 (2H, d, J 7.6 Hz), 7.53 (2H, d, J 8.4 Hz), 7.65 (2H, d, J 8.4 Hz), 7.91 (2H, d, J 9.2 Hz). 13C NMR (100 MHz, DMSO-d3) δ 21.61, 40.65, 42.32, 48.33, 118.95, 125.61, 127.18), 127.26, 128.38, 128.96, 130.02, 130.98, 138.09, 142.47, 143.22, 143.72, 167.55, 170.64. νmax (solid)/(cm−1) 3316, 3277), 1668, 1595, 1531, 1408, 1317, 1254, 1152. MS (API-ES): m/z 451[M−H]− (100%), HRMS (API-ES) m/z found 451.1334 [M−H]−.
