Reaction Steps
Carbamate 39 (4.25 mg, 0.005 mmol) was subjected to the deprotection procedure of PMB described in the preparation of 40. Flash chromatography (EtOAc/hexane 3:2) of the crude product provided 42 (2.8 mg, 92%) as a colorless oil: IR (CHCl3) 3115, 2749, 2328, 1676, 1508, 1215 cm−1; 1H NMR (300 MHz, CDCl3) 6.76 (ddd, 1H, J=16.8, 11.0, 10.1 Hz), 6.18 (t, 1H, J=10.8 Hz), 5.70–5.46 (m, 5H), 5.35 (d, 1H, J=16.8 Hz), 4.49 (dd, J=4.5, 6.6 Hz), 4.82 (d, 2H, J=2.4 Hz), 4.73 (br s, 2H), 4.43 (d, 1H, J=5.1 Hz), 4.15, (m, 1H), 3.78 (m, 1H), 3.56 (s, 3H), 3.54 (s, 3H), 3.36 (t, 2H, J=6.9 Hz), 3.14 (m, 1H), 2.76 (m, 2H), 2.35–2.18 (m, 6H), 2.00–1.60 (m, 7H), 1.22 (d, 3H, J=7.2 Hz), 1.16–1.12 (m, 12H), 1.07 (d, 3H, J=7.2 Hz); 13C NMR (125 MHz, CDCl3) 157.3, 133.7, 133.5, 132.2, 132.0, 130.0, 128.7, 118.0, 109.6, 103.0, 96.5, 82.1, 79.7, 79.1, 72.7, 55.8, 39.9, 39.5, 38.3, 35.5, 35.0, 34.8, 34.6, 30.2, 29.8, 24.3, 18.1, 17.7, 15.7, 15.4, 14.2, 13.2, 8.1; LRMS (ESI) 632.4 (M+Na); HRMS (ESI) calcd for C33H55NO8Na 632.4138, found 632.4139; [α]20D +21.6 (c 0.25, CHCl3).
