[CH2:1]([O:3][C:4]([C:6]1[CH:11]=[CH:10][NH:9][C:8](=[O:12])[CH:7]=1)=[O:5])[CH3:2].C(=O)([O-])[O-].[K+].[K+].C(N(C(C)C)CC)(C)C.[CH3:28][Si:29]([CH3:36])([CH3:35])[CH2:30][CH2:31][O:32][CH2:33]Cl>CN(C)C=O.C(OCC)(=O)C>[CH2:1]([O:3][C:4]([C:6]1[CH:11]=[CH:10][N:9]([CH2:33][O:32][CH2:31][CH2:30][Si:29]([CH3:36])([CH3:35])[CH3:28])[C:8](=[O:12])[CH:7]=1)=[O:5])[CH3:2]
The title compound of example 18.1 (32 g, 191 mmol) and potassium carbonate (132 g, 957 mmol) were stirred in dimethylformamide (350 mL) at room temperature. Diisopropylethylamine (10 mL, 57 mmol) was added via a syringe, followed by 2-(trimethylsilyl)ethoxymethyl chloride (44.0 mL, 249 mmol). The reaction was stirred at room temperature and diisopropylethylamine (56.6 mL, 325 mmol) was added over 5 hours via a pressure equalized addition funnel. The reaction was then stirred overnight at room temperature. When TLC analysis showed that the reaction was complete the reaction mixture was diluted with ethyl acetate and washed four times with water and once with brine. The organic phase was dried over magnesium sulfate, filtered and concentrated. The residue was chromatographed on silica gel in 5-40% ethyl acetate in hexanes to purify the desired product (80%, trace amount of o-alkylated product observed).
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