Reaction Steps
Triisopropylsilyl chloride (0.63 mL, 3.0 mmol, 1.2 equiv) was added to a solution of hemiacetal 223 (0.959 g, 2.49 mmol, 1.00 equiv), imidazole (0.409 g, 6.01 mmol, 2.41 equiv), and 4-dimethylaminopyridine (29 mg, 0.24 mmol, 0.096 equiv) in dimethylformamide (2.5 mL). After 19 h, the yellow solution was concentrated and purified by silica gel chromatography (hexane/ethyl acetate 19:1 to 9:1) to afford 224 (0.800 g, 1.48 mmol, 59% yield) as a colorless oil. Rf=0.49 (hexane/ethyl acetate 4:1); 1H NMR (500 MHz, CDCl3) δ 7.43-7.24 (m, 10H), 4.78 (d, J=11.8, 1H), 4.75 (d, J=11.8, 1H), 4.55 (d, J=11.6, 1H), 4.52 (d, J=12.0, 1H), 4.51 (d, J=7.3, 1H), 3.98 (d, J=3.6, 1H), 3.72 (ddd, J=9.5, 7.3, 2.1, 1H), 3.69-3.58 (m, 3H), 3.56 (dd, J=9.6, 3.7, 1H), 2.26 (d, J=2.2, 1H), 1.19-0.99 (m, 21H); 13C NMR (126 MHz, CDCl3) δ 137.86, 137.84, 128.70, 128.63, 128.08, 128.05, 127.97, 127.93, 98.09, 80.69, 73.81, 73.78, 72.80, 72.01, 68.83, 59.83, 17.96, 17.90, 12.33; FTIR (neat film) 3463.8, 2943.4, 2866.2, 2108.6, 1455.3, 1366.1, 1280.0, 1185.4, 1099.0, 1028.7, 1014.6, 997.6, 883.5, 805.4, 736.3, 695.5, 669.0 cm−1; HRMS (ESI) m/z: Calcd for C29H43N3O5SiNa (M+Na+) 564.2870. found 564.2870.
