Compound 16
(((3aR,4R,4aS,7R,8R,9aS,10R,10aR)-5-Allyl-10-(benzyloxy)-7-bromo-6-((tert-butyldimethylsilyl)oxy)-2,2-dimethyl-4-vinyl-3a,4,7,8,9,9a,10,10a-octahydro-4a,8-epoxycyclohepta[4,5]benzo[1,2-d][1,3]dioxol-8-yl)methoxy)(tert-butyl)dimethylsilane
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InChIKey CEICZFBDFLVUFT-NMBKXTCWSA-N
Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
A solution of thionyl bromide (1.19 mL, 15.4 mmol) in diethyl ether (10 mL) was added over 10 minutes to a –40 °C solution of the allylic alcohol 8a (5.38 g, 7.69 mmol) and pyridine (2.50 mL, 30.9 mmol) in diethyl ether. The reaction was stirred for an additional 10 minutes once the addition was complete, and was then quenched with a saturated solution of sodium bicarbonate (40 mL). The organic phase was partitioned, and the aqueous layer was extracted with diethyl ether (3 x 100 mL). The combined organic extracts were dried over magnesium sulfate and filtered. Concentration and flash chromatography (1:9 diethyl ether: pentane) provided pure 16 (4.821 g, 82%) as well as some recovered starting material (281 mg, 5%). TLC: Rf = 0.6 (1:9 ethyl acetate:pentane), one spot. 1H-NMR (500 MHz, CDCl3, residual solvent peak referenced to 7.24 ppm) δ 7.40-7.24 (m, 5H), 5.89 (ddd, J=17.5, 10.3, 8.8, 1H), 5.69 (dtd, J=17.1, 9.9, 4.6, 1H), 5.26 (dd, J=17.5, 1.5, 1H), 5.17 (dd, J=10.1, 1.8, 1H), 5.16 (s, 1H), 5.15 (dt, J=16.5, 1.6, 1H), 5.05 (dt, J=10.0, 1.7, 1H), 4.93 (d, J=10.3, 1H, AB), 4.38 (d, J=10.3, 1H, AB), 4.32 (dd, J=10.5, 9.4, 1H), 3.81 (dd, J=4.4, 2.1, 1H), 3.67 (d, J=11.5, 1H, AB), 3.61 (d, J=11.4, 1H, AB), 3.49 (dd, J=9.3, 2.1, 1H), 3.41 (ddt, J=14.6, 4.5, 2.0, 1H), 2.82 (dd, J=10.4, 9.0, 1H), 2.55 (ddd, J=14.6, 9.9, 2.3, 1H), 2.50-2.44 (m, 2H), 1.56 (dt, J=11.6, 5.9, 1H), 1.50 (s, 3H), 1.48 (s, 3H), 0.95 (s, 9H), 0.80 (s, 9H), 0.14 (s, 3H), 0.06 (s, 3H), -0.18 (s, 3H), -0.19 (s, 3H) ppm. 13C-NMR (125 MHz, CDCl3) δ 143.17, 138.09, 136.28, 135.22, 128.96, 128.35, 127.83, 123.60, 118.20, 116.48, 110.10, 87.26, 84.08, 82.49, 75.71, 75.44, 73.06, 63.72, 54.95, 49.95, 48.49, 31.50, 30.66, 27.34, 26.73, 25.74, 25.68, 18.23, 18.03, -4.18, -4.48, -5.38, -5.43 ppm. FTIR (thin film) 3075, 3031, 2983, 2954, 2929, 2884, 2857, 1641, 1472, 1463, 1409, 1380, 1369, 1362, 1301, 1256, 1212, 1173, 1143, 1120, 1089, 1076, 1028, 1004, 973, 926, 899, 887, 855, 838, 813, 779, 744, 698, 673 cm-1. HRMS: Calculated for C39H61NaO6Si2 (M+Na+): 783.3087; Found: 783.3127. [α]D = 71.8 ° (c 1.03, CHCl3).
