Reaction Steps
n-BuLi (2.5 M in hexane, 17.6 mL, 44 mmol) was added to a solution of diisopropylamine (6.65 mL, 47.4 mmol) in THF (48 mL) stirred at −78° C. The solution was stirred at −78° C. for 5 min and warmed to 0° C. for 15 min. Borane-ammonia complex (90%, 1.55 g, 45.2 mmol) was added and the resulting mixture was stirred at 0° C. for 15 min, warmed to room temperature for 15 min and then cooled to 0° C. A solution of amide 26 (6.62 g, 11.3 mmol) in THF (35 mL) was added dropwise and the reaction was stirred at 0° C. for 1 h and then at room temperature for 2 h. The mixture was cooled to 0° C. and quenched carefully with saturated aqueous NH4Cl. The mixture was extracted with Et2O and the combined organic extracts were washed with brine, dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (step gradient of 4:1 to 7:3 hexane/EtOAc) to afford the alcohol 27 (4.57 g, 96%) as a colorless oil: IR (film) 3410, 1612, 1513, 1249, 1067, 1038 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.26 (d, J=8.6 Hz, 2H), 6.88 (d, J=8.6 Hz, 2H), 4.44 (d, J=11.7 Hz, 1H), 4.39 (d, J=11.7 Hz, 1H), 3.81 (s, 3H), 3.51 (m, 2H), 3.44 (dd, J=5.6, 3.4 Hz, 1H), 3.37 (dd, J=10.6, 6.5 Hz, 1H), 3.22 (dd, J=9.0, 7.0 Hz, 1H), 2.03-1.95 (m, 1H), 1.78-1.62 (m, 2H), 1.53 (br, 1H), 1.41 (ddd, J=13.5, 7.5, 5.8 Hz, 1H), 0.95 (d, J=6.9 Hz, 3H), 0.94 (d, J=6.7 Hz, 3H), 0.88 (s, 9H), 0.87 (d, J=6.9 Hz, 3H), 0.04 (s, 3H), 0.03 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 159.2, 130.9, 129.4, 113.9, 77.5, 72.8, 67.7, 55.4, 38.3, 38.0, 33.6, 33.2, 26.3, 18.6, 18.0, 15.6, 15.5, −3.5, −3.8; [α]20D−6.3 (c 1.7, CHCl3).
