反应详情

Alcohol 24 (100.0 mg, 0.4057 mmol) was dissolved in 2.0 ml of Et2O and treated with 676 mg of tetrabutylammonium fluoride on silica (1.2 mmol/g, 0.8112 mmol, 2.0 eq) and stirred at 25° C. for 3h at which time alumina (acidic, ca. 1 g) was added. The slurry was filtered through a pad of Celite, concentrated and chromatographed (25 g SiO2, 60% CH2Cl2 /40% EtOac) to yield 27.9 mg of diol 26 (52%) which was protected for characterization. Diol 26 (27.9 mg, 0.211 mmol) was dissolved in 5.0 ml of THF, and treated with 2,2-dimethoxypropane (64 μl, 0.5159 mmol, 2.0 eq) and a crystal of p-toluenesulfonic acid. After 67 h at 25° C., 200 mg of Na2CO3 was added. The mixture was poured onto 7.0 ml of 0.10 M pH 7.0 phosphate buffer, extracted with Et2O (3×10 ml), washed with H2O (1×1 ml), 5% NaHCO3 (2×1 ml), brine (1×1 ml), dried over MgSO4 and concentrated to give 30.0 mg of acetonide 28 as a clear liquid (89%). 1H NMR (CDCl3, 360.134 MHz) δ 4.04 (1H,dd,J=11.56, 2.90 Hz), 3.86 (1H,ddd,J=10.40, 5.29, 2.52 Hz), 3.52 (1H,dd,J=11.44, 0.68 Hz), 1.37 (3H, s), 1.33 (3H, s), 1.45-1.1 (5H,m), 0.99 (3H, d,J=6.92 Hz), and 0.86 (3H,t,J=7.08H). 13C NMR (CDCl3, 90.55 MHz) δ:72.0, 71.2, 67.0, 35.0, 31.7, 29.8, 19.1, 18.5, 14.0, and 10.5. IR (thin film): 2957(m), 2924(s), 2855(m), 1732(br), 1458(m), 1377(w), 1262(m), 1179 9(w), 1074(w), and 800(w) cm-1.

1. additionwas added
2. filtrationThe slurry was filtered through a pad of Celite
3. concentrationconcentrated
4. customchromatographed (25 g SiO2, 60% CH2Cl2 /40% EtOac)