[NH2:1][C:2]1[CH2:7][CH2:6][CH2:5][CH2:4][C:3]=1[C:8]([O:10][CH2:11][CH3:12])=[O:9].N1C=CC=CC=1.[Br:19][CH2:20][CH2:21][CH2:22][CH2:23][C:24](Cl)=[O:25].C(OCC)(=O)C>O1CCCC1>[CH2:11]([O:10][C:8]([C:3]1[CH2:4][CH2:5][CH2:6][CH2:7][C:2]=1[NH:1][C:24](=[O:25])[CH2:23][CH2:22][CH2:21][CH2:20][Br:19])=[O:9])[CH3:12]
In 150 ml of tetrahydrofuran, 42.3 g of ethyl 2-aminocyclohex-1-enecarboxylate as synthesized in above Step 7-1-B was dissolved, to which 40 g of pyridine was added, and then 5-bromovaleryl chloride was dropped thereinto under cooling with ice. Stirring the system for an overnight at room temperature, ethyl acetate was added, followed by washing with saturated aqueous sodium hydrogencarbonate solution, 10% aqueous citric acid and saturated brine, and drying over anhydrous magnesium sulfate. Concentrating the solvent under reduced pressure, the residue was purified on silica gel column chromatography (n-hexane:ethyl acetate=8:1) to provide 76.6 g (92%) of 2-(5-bromopentanoylamino)-cyclohex-1-enecarboxylic acid ethyl ester.
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