Compound 16a

(3aR,4R,4aS,5S,7R,8R,9aS,10R,10aR)-5-Allyl-10-(benzyloxy)-7-bromo-8-(((tert-butyldimethylsilyl)oxy)methyl)-2,2-dimethyl-4-vinyloctahydro-4a,8-epoxycyclohepta[4,5]benzo[1,2-d][1,3]dioxol-6(5H)-one

From: Gateway synthesis of daphnane congeners and their protein kinase C affinities and cell-growth activities

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InChIKey BOZRDNBNHQIDEI-OIPRHVGOSA-N

Compound data: CIF

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

Tetrabutylammonium fluoride (1.0 M in THF, 1.36 mL, 1.36 mmol) was added over 5 minutes to a 0 °C solution of 16 (1.04 g, 1.36 mmol) and acetic acid (78 µL, 1.04 mmol) in THF (25 mL). 30 minutes after the addition was complete, the reaction was quenched with saturated ammonium chloride (25 mL) and extracted with diethyl ether (3 x 25 mL). The combined organic extracts were dried over anhydrous magnesium sulfate and filtered. Concentration and flash chromatography (gradient of 1:9 diethyl ether:pentane to 3:20 diethyl ether:pentane) provided pure α-bromo ketone 16a (0.745 g, 84%) as a white crystalline solid. For X-ray crystallography, the product was recrystallized from Et2O by slowly diffusing pentane vapor into the solution at r.t. m.p.: 130-131°C. TLC: Rf= 0.17 (1:9 ethyl acetate:pentane), one spot. 1H-NMR (500 MHz, CDCl3) δ 7.36-7.27 (m, 5H, Ar-H), 5.97 (dt, 1H, J=17.0 Hz, 9.9 Hz, C18-H), 5.84 (ddd, 1H, J=11.0 Hz, 7.6 Hz, 6.3 Hz, C2-H), 5.30 (dd, 1H, J=10.1 Hz, 1.6 Hz, vinyl), 5.20 (dd, 1H, J=17.3 Hz, 1.5 Hz, vinyl), 5.07 (dd, 1H, J=17.1 Hz, 1.5 Hz, vinyl), 5.00 (dd, 1H, J=10.0 Hz, 1.3 Hz, vinyl), 4.96 (d, 1H, J=10.4, benzylic), 4.90 (s, 1H, C5-H), 4.37 (d, 1H, J=10.4 Hz, benzylic), 4.34 (dd, 1H, J=10.6 Hz, 9.4 Hz, C12-H), 3.85 (dd, 1H, J=5.6 Hz, 2.0 Hz, C14-H), 3.67 (d, 1H, J=11.2 Hz, C20-H), 3.63 (d, 1H, J=11.3 Hz, C20-H), 3.44 (dd, 1H, J=9.3 Hz, 2.0 Hz, C13-H), 2.72 (dd, 1H, J=7.2 Hz, 1.3 Hz, C10-H), 2.60 (dd, 1H, J=8.0 Hz, 6.5 Hz, C1-H), 2.58 (t, 1H, J=10.5 Hz, C11-H), 2.32 (ddd, 1H, J=8.4 Hz, 5.6 Hz, 1.3 Hz, C8-H), 1.97 (ddd, 1H, J=12.2 Hz, 7.7 Hz, 1.1 Hz, C1-H), 1.78-1.69 (m, 2H, C7-H), 1.49 (s, 3H, acetonide), 1.47 (s, 3H, acetonide), 0.81 (s, 9H, t-butyl), -0.11 (s, 3H, Si-CH3), -0.14 (s, 3H, Si-CH3) ppm. 13C-NMR (125 MHz, CDCl3) δ 201.39, 137.78, 136.47, 134.78, 128.57, 128.44, 127.94, 120.76, 116.26, 110.58, 90.12, 86.42, 82.16, 75.70, 75.00, 73.00, 64.74, 60.25, 57.03, 50.51, 43.81, 30.49, 29.77, 27.30, 26.73, 25.72, 18.20, -5.35, -5.47 ppm. FTIR (thin film) 2983, 2929, 2855, 1722, 1456, 1380, 1249, 1183, 1095, 1026, 995, 919, 870, 838, 778, 751, 698 cm-1. HRMS: Calculated for C29H38BrO6Si (M-C4H9+): 591.1600; Found: 591.1611; Calculated for C33H47O6Si (M-Br): 567.3142; Found: 567.3142. [α]D = -15.0 ° (c 1.00, CHCl3). Elemental analysis: Calculated for C33H47BrO6Si: %C = 61.19, %H = 7.31; Found: %C = 61.57, %H = 7.02.