Reaction Steps
A THF (100 mL) solution of 11 (4.35 g, 20.9 mmol, 1 equiv.) was cooled to −78° C. in a 250-mL round-bottom flask, and a cyclohexane solution of sec-butyllithium (1.21 M, 21.6 mL, 26.1 mmol, 1.25 equiv.) was added slowly over 5 min. The resulting yellow slurry was warmed to −30° C. over 40 min and maintained at that temperature for an additional 15 min. The resulting dark orange-red slurry was cooled to −78° C., and a THF (20 mL) solution of 29 (4.98 g, 18.8 mmol, 0.9 equiv.) was added, followed by two THF (10 mL) rinses of the flask that contained 29. At the end of the initial addition of 29, the slurry became faint yellow, and it was allowed to warm slowly to 0° C. over 3.5 h. The slurry was then quenched with H2O at 0° C., producing a mild effervescence. The mixture was warmed to room temperature and extracted thrice with EtOAc. The organic extracts were combined, washed with H2O and brine, dried over Na2SO4, filtered, and concentrated in vacuo to a yellow oil. Flash column chromatography (400 mL SiO2, 9:1 to 8:2 hexane:EtOAc) afforded 4.95 g (12.6 mmol, 67% yield) of 30 as a colorless oil. TLC Rf 0.38 (8:2 hexane:EtOAc). 1H NMR (600 MHz; CDCl3): δ 4.89 (t, J=7.3 Hz, 1H), 4.76 (t, J=3.5 Hz, 1H), 4.72 (t, J=3.5 Hz, 1H), 3.51 (s, 3H), 3.46 (s, 3H), 3.15 (s, 3H), 2.75 (t, J=3.6 Hz, 2H), 2.61 (dd, J=8.0, 3.9 Hz, 1H), 2.34-2.27 (m, 2H), 2.03 (dd, J=13.7, 3.9 Hz, 1H), 1.76 (dd, J=13.7, 8.0 Hz, 1H), 1.62 (s, 3H), 1.54 (s, 3H), 1.51 (m, J=11.0, 5.5, 2.8 Hz, 1H), 1.42-1.37 (m, 2H), 1.35-1.30 (m, 2H), 1.27-1.22 (m, 1H), 1.17 (s, 3H), 1.12 (s, 6H). 13C NMR (126 MHz; CDCl3): δ 154.07, 154.01, 132.5, 120.7, 93.04, 92.93, 74.6, 61.46, 61.26, 54.5, 54.1, 49.3, 46.2, 40.10, 39.90, 34.6, 34.1, 26.1, 25.22, 25.16, 24.2, 19.8, 17.8, 16.8. FTIR (thin film) νmax: 2972, 2912, 2828, 1695, 1659, 1453, 1381, 1364, 1223, 1206, 1151, 1124, 1084, 1033, 973, 952, 849, 779, 689 cm−1. HRMS-ESI (m/z): [M+H]+ calculated for C24H40O4, 393.2999. found, 393.3000.
