76% |
|
General procedure: Compound 2 (2 mmol) was dissolved in anhydrous THF (10 mL) then cooled to -78 C under nitrogen followed by slow addition of 1M LHMDS in THF solution (1.7 mL, 1.7 mmol) over 20 min. The resulting mixture was subsequently stirred at -78 C for 1 h before (R)-(-)-glycidyl butyrate (0.24 g, 1.7 mmol) was added drop wise at -78 C and the mixture was stirred at this temperature for 1 h then allowed to gradually warm to room temperature under stirring for 12 hrs. The reaction was quenched with DDW (10 mL) followed by EtOAc (4 mL). Then the two layers were separated and the aqueous layer was extracted with EtOAc (3×10 mL). The combined organic extracts were washed with saturated aqueous sodium chloride (3×5 mL), dried over Na2SO4, filtered, and concentrated under vacuum. The crude product was then dissolved in DCM (10 mL) and allowed to stand overnight to get a white precipitate which was filtered and washed with DCM. |
65.6% |
|
1.la (6.0 g, 19.6 mmol, 1.0 equiv) was dissolved in THE (60 mL) and cooled to -75 C. nBuLi (1 .51g, 23.5 mmol, 1.2 equiv) was gradually added and the reaction mixture was stirred at -75 C for 1 hour. (R)-oxiran-2-ylmethyl butyrate (2.82 g, 19.6 mmol, 1.0 equiv) was added, the reaction mixture was stirred at -75 C for 1 hour, allowed to attain room temperature, and stirred at room temperature overnight. The reaction mixture was quenched with saturated aqueous ammonium chloride solution and extracted with EtOAc. The organic layer was washed with brine, dried over sodium sulfate and concentrated. The residue was purified by silica gel column chromatography (50-60% EtOAc/Hexane) to afford product 1.lb (3.5 g, 65.6 % yield). LCMS (mlz): 274.1 [M+H]. 1H NMR(400 MHz, DMSO d6) 6 7.64 -7.49 (m, 4H), 5.23 (t, J = 5.7 Hz, 1H), 4.71 (td, J = 9.4, 3.7 Hz, 1H), 4.08 (t, J =9.0 Hz, 1H), 3.82 (dd, J= 8.8, 6.2 Hz, 1H), 3.68 (ddd, J 12.3, 5.5, 3.4 Hz, 1H), 3.56 (ddd, J = 12.3, 5.8, 4.1 Hz, 1H). |