Acetic Acid → (4R)-4-Methyl-4-[2-(1-methylpyrrol-2-yl)ethenyl]-1,3-oxazolidin-2-one

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Reaction Steps

(2R)-2-t-butoxycarbonylamino-1-n-hexanoyloxy-2-methyl-4-(1-methylpyrrol-2-yl)-3-butene (37.0 g, 97.8 mmol) obtained in Reference example 1 (1d) was dissolved in a mixture of tetrahydrofuran (100 mL) and methanol (100 mL) and a 2N aqueous sodium hydroxide solution (100 mL) was added thereto, followed by stirring of the mixture at room temperature for 1 hour. Water and methylene chloride were added to the reaction mixture to separate it. The thus obtained organic phase was separated, washed with a saturated aqueous NaCl solution and dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure to obtain a crude product (28.8 g, yield: quantitative). A solution of potassium t-butoxide (13.2 g, 117 mmol) in tetrahydrofuran (80 mL) was added to a solution of the crude product in tetrahydrofuran (320 mL) under ice-cooling over 10 minutes and the mixture was stirred at the same temperature for 20 minutes. Acetic acid (6.7 mL, 117 mmol) was added to the reaction mixture to neutralize it and the mixture was concentrated under reduced pressure. Water and ethyl acetate were added thereto to separate it. The thus obtained organic phase was separated, washed with a saturated aqueous NaCl solution and dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure and the residue was purified by silica gel chromatography (hexane:ethyl acetate, 1:1-1:2) to obtain the title compound (20.3 g, yield: quantitative).

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