[CH2:1]([O:3][C:4](=[O:12])[CH2:5][C:6]1[N:7]=[C:8]([SH:11])[S:9][CH:10]=1)[CH3:2].Br[C:14]([CH3:23])([CH3:22])[C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16].C(=O)([O-])[O-].[K+].[K+].O>CN(C)C=O>[C:18]([O:17][C:15](=[O:16])[C:14]([S:11][C:8]1[S:9][CH:10]=[C:6]([CH2:5][C:4]([O:3][CH2:1][CH3:2])=[O:12])[N:7]=1)([CH3:23])[CH3:22])([CH3:21])([CH3:20])[CH3:19](2-Mercapto-1,3-thiazol-4-yl)acetic acid ethyl ester (88.6 g) synthesized in Example 1 and tert-butyl 2-bromo-2-methylpropionate (105.3 g) were dissolved in N,N-dimethylformamide (700 mL), potassium carbonate (66.3 g) was added, and the mixture was stirred at room temperature for 8 hr. Water (1 L) was added to the reaction mixture, and the mixture was extracted with ethyl acetate (1 L). The organic layer was washed with saturated brine, and dried over hydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give the title compound (150 g) as a slightly brown oil. The present compound was used in the next step without particular purification.
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