[CH3:1][O:2][C:3](=[O:17])[C:4]1[CH:9]=[CH:8][C:7]([CH2:10]P(OC)(OC)=O)=[CH:6][CH:5]=1.C([N-]C(C)C)(C)C.[Li+].[O:26]([C:31]([N:33]1[CH2:38][CH2:37][C:36](=O)[CH2:35][CH2:34]1)=[O:32])[C:27]([CH3:30])([CH3:29])[CH3:28].O>C1COCC1.C(OCC)(=O)C>[C:27]([O:26][C:31]([N:33]1[CH2:38][CH2:37][C:36](=[CH:10][C:7]2[CH:6]=[CH:5][C:4]([C:3]([O:2][CH3:1])=[O:17])=[CH:9][CH:8]=2)[CH2:35][CH2:34]1)=[O:32])([CH3:30])([CH3:28])[CH3:29]
The crude product (compound 48) was dissolved in dry THF (200 mL) under N2 and cooled to −78° C. Lithium diisopropylamide (32.7 mL 1.5 M in hexanes, 49 mmol) was added dropwise. The solution was allowed to warm to room temperature. A solution of compound 46 (9.76 g, 49 mmol in 100 mL dry THF) was added to the reaction dropwise and was stirred under N2 for 12 hrs. Water (300 mL) and ethyl acetate (300 mL) were added to the reaction mixture and extracted. The aqueous phase was washed with ethyl acetate (2×300 mL). The combined ethyl acetate was dried over MgSO4 and evaporated to give a crude product, which was purified by silica gel chromatography (0-33% ethyl acetate in hexanes) to provide compound 49 as a white solid (5.64 g, 35%).
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