A solution of 917 mg (1.52 mmoles) of (1S,2RS,-3RS,5S,6S,7R)-3-methanesulfonyloxymethyl-2,3-epoxy-6-[(E,3S)-3-t-butyldimethylsilyloxy-1-octenyl]-7-t-butyldimethylsilyloxybicyclo[3.3.0]octane obtained in Example 2 in 3 ml of tetrahydrofuran was added to an anion radical solution prepared by reacting naphthalene (1.28 g, 10 mmoles) with sodium (207 mg, 9 mmoles) in 30 ml of tetrahydrofuran at room temperature for I hour. The mixture was stirred at room temperature for 10 minutes and 3.0 g of ammonium chloride was added to the reaction solution. Then, a saturated aqueous solution of ammonium chloride was added and the resulting mixture was extracted with ethyl acetate. The organic layer was washed with an aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate and concentrated to give a crude product. It was subjected to column chromatography (silica gel 50 g; hexane/ethyl acetate=19/1) to give (1S,2RS,5S,-6S,7 R)-2-hydroxy-3-methylene-6-[(E,3S)-3-t-butyldimethylsilyloxy- 1-octenyl) -7-t-butyldimethylsilyloxybicyclo[3.3.0]octane (605 mg, 1.19 mmoles, 78%).
