Reaction Steps
Dry MeOH (1.05 mL, 26.0 mmol) then LiBH4 (13 mL, 2.0 M solution in THF, 26 mmol) were added to a stirred solution of 20 (4.79 g, 8.62 mmol) in THF (75 mL) at 0° C. The resulting mixture was stirred at 0° C. for 45 min and at room temperature for 1 h. The solution was cooled to 0° C. and treated carefully with a 1.0 M aqueous NaOH (50 mL). The phases were separated and the aqueous phase was extracted with CH2Cl2. The combined organic phases were washed with brine, dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (hexane/EtOAc 7:3) to give the alcohol 21 (2.98 g, 90%) as a colorless oil: IR (film) 3425, 1613, 1513, 1463, 1249, 1091, 1037 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.26 (d, J=8.5 Hz, 2H), 6.88 (d, J=8.5 Hz, 2H), 4.47 (d, J=11.7 Hz, 1H), 4.40 (d, J=11.7 Hz, 1H), 3.84 (s, 3H), 3.75 (dd, J=5.7, 2.9 Hz, 1H), 3.52 (m, 3H), 3.28 (dd, J=9.1, 7.1 Hz, 1H), 2.10 (br, 1H), 2.05 (m, 1H), 1.93-1.81 (m, 1H), 0.97 (d, J=7.0 Hz, 3H), 0.90 (s, 9H), 0.87 (d, J=7.1 Hz, 3H), 0.07 (s, 3H), 0.05 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 159.2, 130.7, 129.3, 113.8, 74.8, 72.8, 72.7, 66.3, 55.4, 39.0, 37.7, 26.2, 18.4, 15.2, 12.0, −4.1; HRMS (ESI) calcd for C18H31O3SiNa 323.2042 [M+Na]+, found 323.2035; [α]20D−0.76 (c 2.9, CHCl3).
