“…1 H NMR (500 MHz, CDCl 3 ): δ 6.44 (br s, 1H), 4.77 (m, 1H), 4.18 (q, 2H, J = 7.2 Hz), 3.13−3.04 (m, 2H), 2.48 (d, 1H, J = 16.5 Hz), 2.36 (d, 1H, J = 18.5 Hz), 1.83−1.65 (m, 4H), 1.54−1.23 (m, 6H), 1.31 (s, 3H), 1.28 (t, 3H, J = 7.2 Hz). 13 (20). The following reaction was carried out under Ar.…”