Reaction Steps
colorless crystals, mp: 240° C.; [α]D24−38.0° (c 2.41, CHCl3); 1H NMR (CDCl3) δ 5.31 (s, 1H), 5.00 (brs 1 H), 4.53 (q, J=7 Hz, 1H), 4.24 (brs 1H), 2.69 (dd, J=14.5, 3.5 Hz, 1H), 2.61 (d, J=6.5 Hz, 1H), 2.28 (m, 1H), 2.12 (m, 1H), 2.06 (m, 1H), 2.04 (s, 3H), 1.87 (m, 1H), 1.82 (m, 2H), 1.74 (m, 1H), 1.71 (m, 2H), 1.64 (m, 1H), 1.61 (dd, J=14.5, 4 Hz, 1H), 1.48 (m, 3H), 1.41 (s, 3H), 1.41 (m, 1H), 1.34 (m, 1H), 1.29 (s, 3H), 1.27 (m, 1H), 1.18 (m, 2H), 1.00 (s, 3H), 096 (s, 3H), 0.93 (d, J=7 Hz, 3H), 0.79 (m, 1H); 13C NMR (CDCl3) δ 170.6 s, 117.9 s, 101.3 d, 90.7 s, 84.7 s, 80.6 d, 70.0 d, 66.0 d, 64.3 d, 58.5 d, 56.1 s, 56.0 d, 41.1 d, 40.5 d, 39.2 t, 38.7 t, 35.9 s, 32.4 t, 33.7 t, 32.1 t, 32.1 t, 31.0 d, 29.0 q, 27.4 t, 25.6 t, 22.8 q, 21.4 q, 19.6 q, 14.4 q, 13.9 q; positive NOEs: H-6β/H-8, H-8/H-18, H-12β/H-21, H-12α/H-16, H-14/H-16, H-15β/H-18, H-16/H-17, H-17/H-21, and H-21/H-23α; IR (KBr) 3470, 3300, 1730, 1240 cm−1; EIMS m/z 500 (M−H2O), 485 (4), 442 (4), 372 (100%). The stereochemistry at C-18 was elucidated to be R configuration by positive NOEs between the proton pairs: H-18/H-8 and H-18/H-15β.
