A solution of 12 mg of 3-benzoyl-7-fluoro-2-methoxycarbonyl-1,2,3,4-tetrahydroisoquinoline in 2 mL of a 6 N aqueous hydrochloric acid solution was reacted under reflux for 16 hours. Under ice-cooling, the reaction liquid was diluted by addition of water, alkalized with 5 N sodium hydroxide, and extracted with chloroform. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain a yellow oily substance. 10 mg of the obtained yellow oily substance and 3 mg of 10% Pd-C were dissolved in 2 mL of ethanol and 0.2 mL of a 4N hydrochloric acid/ethyl acetate solution, followed by stirring at room temperature for 48 hours under a hydrogen atmosphere. The reaction liquid was filtered through Celite, and the filtrate was concentrated under reduced pressure to obtain 8 mg of a yellow oily substance. To a solution of 8 mg of the yellow oily substance and 9 mg of N-Boc-2-benzylaminoethanol in 1 mL of toluene were sequentially added 9 mg of sodium triacetoxyborohydride and 5 mg of acetic acid, followed by stirring at room temperature for 2 hours. It was alkalized by addition of an aqueous sodium bicarbonate solution, followed by extraction with ethyl acetate. The organic layer was washed with brine and then dried over anhydrous sodium sulfate, and the solvent was removed by evaporation to obtain 10 mg of a yellow oily substance. To this yellow oily substance was added 2 mL of 4N hydrochloric acid/ethyl acetate, followed by stirring at room temperature for 30 minutes. The organic layer was washed with an aqueous sodium bicarbonate solution and then with brine, and then dried over anhydrous sodium sulfate, and the solvent was removed by evaporation. The residue obtained was purified using silica gel chromatography (chloroform: methanol=10:1) to obtain 2 mg (yield 41%) of a title compound as a yellow oily substance.
