Potassium Hydroxide → 2-(5,6-dihydro-2H-4-pyranyl)-5-methanesulfonylindole

To a solution of the compound obtained in Example 14 (3) (28.8 mg) in methanol (3 ml), a 1N aqueous potassium hydroxide solution (0.69 ml) was added and the mixture was stirred at 100° C. for 1 hour. The reaction solution was then poured into a saturated aqueous sodium hydrogencarbonate solution, extracted with dichloromethane, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to obtain 16.5 mg of the desired product as a white powder.