Reaction Steps
A flame-dried round-bottom flask with magnetic stir bar was charged with 380 mg (0.939 mmol, 1 equiv.) starting material 50 followed by 9.4 mL THF and 596 μL (4.70 mmol, 5 equiv.) of chlorotrimethylsilane with stirring. The solution was cooled in an acetone/dry ice bath for 10 minutes prior to the addition of 9.4 mL of a 0.5M solution of lithium tetramethylpiperidide in THF (4.7 mmol, 5 equiv.). The mixture was stirred at −78° C. for 10 minutes before placing the reaction in a water/ice bath for an additional 10 minutes. The reaction was quenched by the addition of 2 mL of saturated aqueous sodium bicarbonate and transferred to a separatory funnel by the addition of 50 mL hexane. The organic layer was then washed with saturated aqueous sodium bicarbonate, 10% aqueous hydrochloric acid, water, and saturated brine solution. The organic layer was then dried with MgSO4 and concentrated in vacuo to give a yellow oil. Purification by silica gel chromatography (Rf=0.25 in 9:1 hexane:ethyl acetate) gave 425 mg (95% yield) of 51 as a clear oil. 1H NMR (500 MHz, CDCl3) δ ppm 5.06 (tt, J=7.0, 1.3 Hz, 1H), 4.99 (tt, J=6.9, 1.4 Hz, 1H), 4.59 (dd, J=35.6, 6.8 Hz, 2H), 3.92 (s, 3H), 3.60 (dd, J=11.5, 5.2 Hz, 2H), 3.33 (s, 3H), 3.17 (s, 1H), 2.55 (dd, J=14.5, 6.3 Hz, 1H), 2.38-2.38 (m, 0H), 2.40 (dd, J=14.6, 7.4 Hz, 1H), 2.27-2.34 (m, 1H), 2.24 (dd, J=13.5, 5.2 Hz, 4H), 1.84-1.94 (m, 1H), 1.81 (dd, J=13.4, 11.6 Hz, 2H), 1.63-1.68 (m, 12H), 1.55 (ddd, J=13.0, 4.5 Hz, 1H), 1.17-1.26 (m, 1H), 0.91 (s, 3H), 0.23-0.24 ppm (m, 9H). 13C NMR (126 MHz, CDCl3) δ ppm 205.9, 197.8, 185.8, 134.2, 131.8, 127.4, 124.4, 119.4, 97.3, 79.2, 70.8, 64.4, 58.4, 55.8, 46.5, 37.7, 37.4, 29.8, 26.0, 25.9, 21.6, 18.1, 17.8, 16.4, 0.7. HRMS-ESI (m/z): [M+H]+ calculated C27H44O5Si, 477.3031. found 477.3031.
