反应详情

A solution of 5 (25.5 g, 71.73 mmol) in THF (300 mL) and water (75 mL) under Ar is cooled to 0° C. To this is added via syringe H2O2 (30% in water, 30.6 mL, 0.300 mol) gradually over a period of 15 minutes. LiOH·H2O (4.92 g, 0.12 mol) in water (150 mL) is added via syringe. The mixture is stirred for 3 h after which the septum is removed and Na2SO3 (37.8 g, 0.300 mol) in water (225 mL) is added slowly. The bulk of the THF is removed by rotavap at a bath temperature between 25-30° C. The residue is extracted with CH2Cl2 (100 ml×3). The combined organic layer is washed consecutively with 0.5 N HCl (100 mL), sat. NaHCO3 (100 mL), water (100 mL) and brine (100 mL). The solution is then dried over Na2SO4 and concentrated in vacuo. The residue is recrystallized in hexane/ethyl acetate to afford the Evan's chiral auxiliary 2 as white needles. The aqueous layer from the first extraction was acidified to pH 1 and extracted with ethyl acetate (100 mL×3). The combined organic layer is washed with 0.5 N HCl (100 mL) and then brine (100 mL). It is then dried over Na2SO4 and concentrated to yield 6 as a colorless oil (17.198 g, 70.39 mmol, 98%). 1H NMR (400 MHz, CDCl3) δ 0.88 (t, J=6.8 Hz, 3H), 1.21-1.37 (m, 6H), 1.43 (s, 9H), 1.40-1.70 (m, 2H), 2.61 (dd, J=9.3 Hz, 1H), 2.38 (dd, J=16.4, 5.1, 1H), 2.61 (dd, J=16.4, 9.3, 1H), 2.78 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 13.9, 17.5, 17.9, 22.3, 26.5, 27.9, 31.5, 37.0, 41.3, 94.9, 80.0, 171.1, 181.1. HRMS calcd for C13H25O4 (MH+): 245.1752. Found (DCI): 245.1766 (Δ=5.2 ppm).

1. customis removed
2. customThe bulk of the THF is removed by rotavap at a bath temperature between 25-30° C
3. extractionThe residue is extracted with CH2Cl2 (100 ml×3)
4. washThe combined organic layer is washed consecutively with 0.5 N HCl (100 mL), sat. NaHCO3 (100 mL), water (100 mL) and brine (100 mL)
5. dry with materialThe solution is then dried over Na2SO4
6. concentrationconcentrated in vacuo
7. customThe residue is recrystallized in hexane/ethyl acetate