Sodium Hydroxide → (4R)-4-methyl-4-[2-(1-ethylpyrrol-2-yl)ethenyl]-1,3-oxazolidin-2-one

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Reaction Steps

(2R)-2-t-Butoxycarbonylamino-2-methyl-4-(1-ethylpyrrol-2-yl)-1-n-hexanoyloxy-3-butene (11.7 g, 29.8 mmol) obtained in Reference example 3 (3b) was dissolved in a mixture of tetrahydrofuran (40 mL) and methanol (40 mL) and a 2N aqueous sodium hydroxide solution (40 mL) was added thereto, followed by stirring of the mixture at room temperature for 1 hour and 30 minutes. Acetic acid (1.5 mL) was added to the reaction mixture to stop the reaction and water and ethyl acetate were added thereto to separate it. The thus obtained organic phase was separated, washed with water and 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 (8.7 g). A solution of potassium t-butoxide (4.0 g, 35.6 mmol) in tetrahydrofuran (30 mL) was added to a solution of the crude product (8.7 g) in tetrahydrofuran (100 mL) under ice-cooling over 10 minutes, followed by stirring of the mixture at the same temperature for 1 hour. Acetic acid (2 mL) was added to the reaction mixture to neutralize it, and the mixture was concentrated under reduced pressure and water and ethyl acetate were added thereto to separate it. The thus obtained organic phase was 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, 3:2) to obtain the title compound (5.7 g, yield: 86%).

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