C(Cl)Cl.[OH:4][CH2:5][CH2:6][CH2:7][CH2:8]/[CH:9]=[C:10](\[CH3:16])/[C:11]([O:13][CH2:14][CH3:15])=[O:12].N1C=CN=C1.[Si:22](Cl)([C:25]([CH3:28])([CH3:27])[CH3:26])([CH3:24])[CH3:23]>CN(C)C=O>[O:4]([CH2:5][CH2:6][CH2:7][CH2:8]/[CH:9]=[C:10](\[CH3:16])/[C:11]([O:13][CH2:14][CH3:15])=[O:12])[Si:22]([C:25]([CH3:28])([CH3:27])[CH3:26])([CH3:24])[CH3:23]To a methylene chloride solution (300 ml) of Ester 3 (13.91 g; 0.0748 mol), 43 ml of DMF (dimethylformamide) and imidazole (7.6 g; 0.112 mol) are added and the whole is stirred until imidazole is fully dissolved. Tert-butyldimethylsilyl chloride (13.5 g; 0.0897 mol) is then added thereto and the whole is stirred for 20 min. After stirring, the resultant solution is quenched using a buffer solution (100 ml) and the organic compound is extracted three times with ethyl acetate, followed by the wash of the organic layer in a saturated saline solution and drying over anhydrous magnesium sulfate. After anhydrous magnesium sulfate is filtered and the solvent is distilled off under reduced pressure, the residue is separated and purified by column chromatography (developing solution, ethyl acetate:hexane=1:1) to produce Ester 4 (22.16 g; 0.0739 mol) of 99% in yield.
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