[CH2:1]([O:8][C:9]([N:11]1[CH2:16][CH2:15][CH:14]([CH2:17][CH2:18][CH2:19][CH2:20][C:21]([OH:23])=[O:22])[CH2:13][CH2:12]1)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C(=O)([O-])O.[Na+].[CH2:29](I)[CH3:30].CN(C)C=O>O>[CH2:1]([O:8][C:9]([N:11]1[CH2:12][CH2:13][CH:14]([CH2:17][CH2:18][CH2:19][CH2:20][C:21]([O:23][CH2:29][CH3:30])=[O:22])[CH2:15][CH2:16]1)=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1A mixture of 54.8 g of 5-(1-benzyloxycarbonyl-4-piperidyl)valeric acid, 29 g of sodium hydrogen-carbonate, 21 ml of ethyl iodide and 150 ml of N,N-dimethylformamide is heated at 70° to 80° C. with stirring for 3 hours. Ethyl iodide (10 ml) is additionally added to the reaction solution, followed by heating at 90° to 100° C. for 3 hours. After cooling, 1 l of water is added to the reaction solution, and the mixture is extracted with 1 l of ethyl acetate. The extract is washed with water, 1N hydrochloric acid and dilute aqueous sodium hydrogencarbonate solution successively, dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give 58 g of ethyl 5-(1-benzyloxycarbonyl-4-piperidyl)valerate as pale yellow oil.
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