534 mg of {1-[8-(4-Methoxy-phenyl)-1,4-dioxa-spiro[4.5]dec-8-yl]-propyl}-carbamic acid benzyl ester (96) were dissolved in 1 mL of a 2:1 mixture of acetone and 6N aqueous hydrochloric acid. The reaction mixture was stirred for 16 h at room temperature, then dropped into 150 mL of saturated aqueous sodium bicarbonate solution. The phases were separated and the aqueous phase was extracted three times with dichloromethane (100 mL each). The combined organic phases were dried over magnesium sulphate, filtered and concentrated to give the ketone 97. Rt=1.58 min (Method 19). Detected mass: 396.3 (M+H+).
