Palladium chloride (100 mg) and cupric chloride dihydrate (50 mg) were added to DMF solution (30 ml) of 2-t-butoxycarbonyl-9-allyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (1.90 g, 6.1 mmol) and stirred at room temperature for 18 hours. The reaction solution was mixed with ethyl acetate, washed with water and dried with anhydrous sodium sulfate, and then the solvent was removed by evaporation under a reduced pressure, the thus obtained residue was mixed with diisopropyl ether (20 ml) and the thus precipitated crystals were collected by filtration to obtain 1.17 g of the title compound (59% in yield).
