Formic Acid → 5-(N-methylamino)-2-phenyl-1,3,4,5-tetrahydrobenz[cd]indole

A portion (100 mg) of the compound obtained in Example 81 was suspended in tetrahydrofuran (THF; 3 ml) and to the suspension was added a solution (1M; 0.5 ml) of an acid anhydride prepared from acetic anhydride and formic acid in THF at -20° C. The mixture was stirred for 20 minutes. The solid obtained by concentrating the reaction mixture was suspended in THF (3 ml) and to the suspension was added a solution of borane-methyl sulfide complex in THF (10M; 100 μl). The mixture was heated to reflux for 1 hour and allowed to cool. 3N solution (10 ml) of hydrochloric acid in methanol was added to the reaction mixture, followed by stirring for 1 hour at room temperature. The reaction mixture was made basic with 3N aqueous solution of sodium hydroxide and extracted with ethyl acetate. The organic layer was washed with saturated aqueous solution of sodium chloride and dried over anhydrous sodium sulfate. Then, the solvent was distilled off under reduced pressure to yield 90 mg (85%) of the titled compound.