To a solution of ethyl 9-(2-aminoethyl)-8,9-dihydro-7H-cyclopenta[c]pyrazolo[1,5-a]pyridine-1-carboxylate (45.0 mg, 0.165 mmol) in tetrahydrofuran (1.7 mL) was added 1.5M diisobutylaluminum hydride toluene solution (1.3 mL, 1.95 mmol) at room temperature, and the mixture was stirred for 3 hr. Sodium sulfate decahydrate (1.3 g) was added, and the mixture was filtered through celite, and the filtrate was concentrated under reduced pressure. To a mixture of the residue and triethylamine (34.5 μL, 0.248 mmol) in tetrahydrofuran (1.7 mL) was added acetic anhydride (23.4 μL, 0.248 mmol) under ice-cooling, and the mixture was stirred at room temperature for 15 min. Water (50 μL) was added, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (methanol/ethyl acetate=0/100→5/95) and recrystallization (ethyl acetate/diisopropyl ether) to give the title compound (7.3 mg, yield 17%).
