C[Si]([N-][Si](C)(C)C)(C)C.[Li+].[C:11]([O:14][CH2:15][CH3:16])(=[O:13])[CH3:12].C[O:18][C:19]([CH:21]1[CH2:25][CH2:24][O:23][CH2:22]1)=O>C1COCC1>[CH2:15]([O:14][C:11](=[O:13])[CH2:12][C:19](=[O:18])[CH:21]1[CH2:25][CH2:24][O:23][CH2:22]1)[CH3:16]To a solution of lithium bis(trimethylsilyl)amide (1 M in hexanes; 100 mL) in THF (200 mL) at −78° C. was added dry ethyl acetate (10.8 g, 12 mL, 122.5 mmol) dropwise. After 30 min at −78° C., the mixture was treated with a solution of tetrahydro-furan-3-carboxylic acid methyl ester (6.0 g, 46.1 mmol) in THF (50 mL). After 4 h at −78° C., the reaction was quenched with satd. aq. NH4Cl, warmed to rt, and extracted with EtOAc (5×75 mL). The combined organic layers were washed with satd. aq. NaCl, dried, and concentrated to give a colorless oil. Chromatography on SiO2 (EtOAc/CH2Cl2) afforded the title compound (3.3 g).
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