To a solution of the compound obtained in Example 30 (4) (0.1722 g) in ethanol (14 ml), potassium hydroxide (0.047 g) was added and the mixture was stirred at 15 to 30° C. for 30 minutes. To the mixture was added 10% aqueous hydrochloric acid solution, and the mixture was extracted with ethyl acetate, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The resulting residue was separated using silica gel column chromatography (hexane:ethyl acetate=1:1) to obtain 0.0748 g of the desired product.
