1H NMR (400 MHz, CDCl3) δ 7.76 (d, J = 7.6 Hz, 2H), 7.60 (dd, J = 7.2, 3.9 Hz, 2H), 7.40 (t, J = 7.2 Hz, 2H), 7.31 (t, J = 7.5 Hz, 2H), 5.26 (d, J = 8.6 Hz, 1H), 4.31–4.51 (m, 3H), 4.23 (t, J = 7.1 Hz, 1H), 3.75 (s, 3H), 1.78–1.93 (m, 1H), 1.60–1.76 (m, 1H), 1.45–1.60 (m, 1H), 1.05–1.34 (m, 2H), 0.88 (d, J = 4 Hz, 3H), 0.86 (d, J = 4 Hz, 3H); MS (APCI+) for C23H27NO4m/z 160.1 (M-Fmoc+H)+.