Potassium Carbonate → Methyl (4S)-2-[5-(3-[(1S)-2-methoxy-1-methylethoxy]-5-{[6-(methylsulfonyl)pyridin-3-yl]oxy}phenyl)-1H-pyrrol-2-yl]-4,5-dihydro-1,3-oxazole-4-carboxylate

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Reaction Steps

Methyl N-{[5-(3-[(1S)-2-methoxy-1-methylethoxy]-5-{[6-(methylsulfonyl)pyridin-3-yl]oxy}phenyl)-1H-pyrrol-2-yl]carbonyl}-L-serinate (1.91 g, 3.57 mmol) synthesized in Example (86a) was dissolved in methylene chloride (40 mL), and bis(2-methoxyethyl)aminosulfur trifluoride (0.85 mL, 4.64 mmol) was added dropwise at −78° C. After stirring for 30 minutes under nitrogen atmosphere, potassium carbonate (0.74 g, 5.35 mmol) was added, and stirring was carried out at 0° C. for 10 minutes, followed by further stirring at room temperature for 3 hours. A saturated aqueous sodium hydrogencarbonate solution (30 mL) was added, followed by extraction with methylene chloride (100 mL), and the organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure, and the resulting residue was purified using silica gel column chromatography (elution solvent: ethyl acetate/hexane=30%-70%) to afford the desired compound (1.76 g, 93%) as a white powder.

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