Reaction Steps
General procedure II for Mitsunobu coupling: To a solution of 21 (0.64 g, 5.59 mmol), 7 (1.74 g, 5.59 mmol) and triphenylphosphine (2.93 g, 11.2 mmol) in THF (50 mL) was added diisopropylazodicarboxylate (2.26 g, 11.2 mmol) dropwise. The reaction mixture was stirred at room temperature for 4 hours and concentrated under vacuum. The residue was purified by column chromatography on silica using methylene chloride and methanol (10:1) as eluent to afford 28a as colorless foam (1.48 g, 63%). 1H MNR (400 MHz, CDCl3) δ 8.28 (s, 1H), 7.55 (s, 1H), 7.45˜7.38 (m, 5H), 7.29 (d, J=8.0, 1H), 6.87 (d, J=8.0, 1H), 5.25 (s, 2H), 4.49 (m, 1H), 2.72˜2.68 (m, 2H), 2.52˜2.49 (m, 2H), 2.38 (s. 3H), 2.35 (s, 1H), 2.11˜2.05 (m, 2H), 1.96˜1.92 (m, 2H). 13C MNR (100 MHz, CDCl3) δ 159.1, 156.8, 153.4, 149.4, 135.8, 128.9, 128.7, 128.4, 125.3, 122.5, 121.6, 115.4, 113.5, 110.7, 77.4, 67.6, 52.4, 46.4, 30.8, 8.6. IR (film) νmax 3406, 3319, 2939, 2849, 2791, 1711, 1609, 1524, 1366, 1271, 1227, 1204, 1103, 1038, 1024 cm−1. HRMS (ESI+) m/z Calc for [M+H+] C24H27N2O5 423.1920. found 423.1920.
