Compound 8a

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InChIKey YMEBLHYKXMWBRJ-CMISRATASA-N

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

Iodine (10 mg, 0.04 mmol) was added to a roundbottom flask containing a suspension of magnesium powder (502 mg, 20.7 mmol) in diethyl ether (35 mL). The reaction was brought to reflux and then immediately cooled to room temperature and stirred for 30 minutes, at which time the color of the solution had turned from deep yellow to a cloudy grey. The reaction vessel was cooled to 0 °C and a solution of allyl bromide (1.80 mL, 20.7 mmol) and 8 (5.43 g, 8.26 mmol) in diethyl ether (55 mL) was added dropwise over 30 minutes. The reaction was stirred for an additional 30 minutes at 0 °C upon completion of the addition, and then quenched with saturated ammonium chloride (70 mL). The organic layer was partitioned and the aqueous phase was extracted with diethyl ether (3 x 100 mL). The combined organic phases were washed with brine (100 mL) and then dried over anhydrous magnesium sulfate and filtered. Concentration and flash chromatography (gradient of pentane to 1:9 diethyl ether:pentane) provided pure alcohol 8a (5.38 g, 93%) as a colorless oil. TLC: R_f = 0.5 (1:9 ethyl acetate:pentane), one spot. ¹H-NMR (500 MHz, CDCl₃, residual solvent peak referenced to 7.24 ppm) δ 7.34-7.22 (m, 5H), 6.04 (ddd, J=17.5, 10.4, 8.4, 1H), 5.87 (dtd, J=18.3, 9.2, 5.7, 1H), 5.21 (dd, J=17.5, 0.9, 1H), 5.14 (dd, J=10.4, 1.5, 1H), 4.94 (d, J=14.3, 1H), 4.93 (d, J=11.7, 1H), 4.87 (s, 1H), 4.86 (d, J=11.6, 1H, AB), 4.52 (d, J=11.7, 1H, AB), 4.17 (t, J=10.0, 1H), 4.06 (dd, J=7.8, 2.6, 1H), 3.74 (dd, J=9.8, 2.4, 1H), 3.65 (d, J=10.0, 1H, AB), 3.62 (d, J=10.1, 1H, AB), 3.08 (dt, J=9.9, 8.2, 1H), 2.93 (dd, J=10.5, 8.5, 1H), 2.65 (dd, J=13.8, 5.7, 1H), 2.41 (s, 1H), 2.38 (dd, J=13.9, 9.3, 1H), 2.26 (dd, J=11.2, 10.3, 1H), 1.71 (dd, J=11.4, 8.3, 1H), 1.46 (s, 3H), ,1.43 (s, 3H), 0.90 (s, 9H), 0.87 (s, 9H), 0.14 (s, 3H), 0.13 (s, 3H), 0.03 (s, 6H) ppm. ¹³C-NMR (100 MHz, CDCl₃) δ 149.39, 139.00, 137.27, 135.71, 128.16, 127.69, 127.29, 117.02, 116.56, 110.75, 104.30, 87.81, 81.90, 81.17, 77.93, 74.38, 74.22, 73.18, 66.69, 48.19, 44.81, 42.57, 38.87, 27.58, 26.93, 25.77, 25.68, 18.14, 18.05, -4.37, -4.89, -5.39 ppm. FTIR (thin film) 3574, 3075, 3031, 2954, 2930, 2886, 2858, 1660, 1472, 1368, 1286, 1254, 1173, 1150, 1095, 1028, 1006, 975, 913, 888, 814, 779, 696 cm^-1. HRMS: Calculated for C₃₉H₆₂O₇Si₂ (M): 698.4035; Found: 698.4035. [α]_D = -9.3 ° (c 0.60, CHCl₃). Elemental analysis: Calculated for C₃₉H₆₂O₇Si₂: %C = 67.01, %H = 8.94; Found: %C = 67.21, %H = 9.12.