Hexane → ethyl (9R)-9-{2-[(tert-butoxycarbonyl)amino]ethyl}-2-methyl-8,9-dihydro-7H-cyclopenta[c]pyrazolo[1,5-a]pyridine-1-carboxylate

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Ethyl 9-{2-[(tert-butoxycarbonyl)amino]ethyl}-2-methyl-8,9-dihydro-7H-cyclopenta[c]pyrazolo[1,5-a]pyridine-1-carboxylate (300 mg) was fractionated by high performance liquid chromatography (instrument: Prep LC 2000 (manufactured by Nihon Waters K.K.), column: CHIRALPAK AD (50 mm ID×500 mm L, manufactured by Dicel Chemical Industries, Ltd.), mobile phase: A) hexane 100%, B) hexane/ethanol=70/30, mixing ratio: A/B=80/20, flow rate: 60 mL/min, column temperature: 30° C., sample concentration: 10 mg/mL (hexane/ethanol=95/5), injection amount: 300 mg). A fraction solution containing an optically active compound having a longer retention time under the above-mentioned high performance liquid chromatography conditions was concentrated to give the title compound (140 mg, 99.7% ee). The enantiomer excess (ee) was measured by high performance liquid chromatography (column: CHIRALPAK AD (4.6 mm ID×250 mm L, manufactured by Dicel Chemical Industries, Ltd.), mobile phase: hexane/ethanol=95/5, flow rate: 0.5 mL/min, column temperature: 30° C., sample concentration: 0.25 mg/mL (hexane/ethanol=95/5), injection volume: 10 μL).

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