m-Chloroperbenzoic acid (777 mg, 4.5 mmoles) was added to a solution of (4S,5S)-4,5-bis(benzoyloxymethyl)-1-cyclohexene (1.05 g, 3.0 mmoles) in methylene chloride (6 ml) under cooling with ice. After stirring the mixture at room temperature for 2 hours, a saturated aqueous solution of sodium hydrogen sulfite was added to the reaction mixture and the excessive peracid was decomposed, after which a saturated aqueous solution of sodium hydrogen carbonate was added and the whole mixture was subjected to extraction with ethyl ether. The ether extract solution was washed with water and then with saturated aqueous solution of sodium hydrogen carbonate, and dried on anhydrous sodium sulfate. After distilling off the solvent therefrom under reduced pressure, the residue was purified by silica gel column chromatography (ethyl acetate:n-hexane=1:3, v/v) to obtain (3S,4S)-3,4-bis(benzoyloxymethyl)-7-oxabicyclo[4.1.0]heptane (1.025 g, Yield 93%).
