To a solution of alcohol 181 (1.0 g, 4.16 mmol) in dichloromethane (40 mL) at room temperature under nitrogen atmosphere were successively added solid t-butyldimethylsilyl chloride (815 mg, 5.41 mmol), imidazole (340 mg, 4.99 mmol), and a catalytic amount of 2,6-dimethylaminopyridine. The mixture was stirred over 1 hour and triethylamine (696 μL, 4.99 mmol) was added. The mixture was stirred for 2 days. The reaction was quenched with water and the layers separated. The aqueous layer was extracted with dichloromethane and the combined organic layers were washed successively with a 1N HCl (2×10 mL), a saturated solution of sodium bicarbonate and brine, dried (MgSO4) and concentrated in vacuo. The crude residue was purified by flash chromatography using hexane as the eluent, and affording the title compound 182 in 84% yield (1.24 g). 1H NMR: (300 MHz, CDCl3) δ: 7.83-7.79 (m, 3H), 7.70 (s, 1H), 7.47-7.40 (m, 3H), 5.78 (ddt, J=17.0, 10.4, 6.6 Hz, 1H), 5.85-5.71 (m, 2H), 4.79 (dd, J=6.9, 4.9 Hz, 1H), 2.04-1.98 (m, 2H), 1.80-1.54 (m, 2H), 0.90 (s, 9H), 0.04 (s, 3H), −0.14 (s, 3H). MS (ESI)=223 (MH+-TBSO).
