[N:1]1([C:11]([N:13]2[CH2:18][CH2:17][CH:16]([C:19]([O:21]CC)=[O:20])[CH2:15][CH2:14]2)=[O:12])[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH2:4][CH2:3][CH2:2]1.[OH-].[Na+]>C(O)C>[N:1]1([C:11]([N:13]2[CH2:18][CH2:17][CH:16]([C:19]([OH:21])=[O:20])[CH2:15][CH2:14]2)=[O:12])[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH2:4][CH2:3][CH2:2]111.2 g of ethyl 1-(3,4-dihydroquinolin-1(2H)-ylcarbonyl)piperidine-4-carboxylate, 443 ml of ethanol and 163 ml of 1N aqueous sodium hydroxide solution are introduced into a 1 l round-bottomed flask. The reaction medium is heated at 50° C. for 4 h 30. The ethanol is evaporated under reduced pressure and a 1N aqueous hydrochloric acid solution is subsequently added. The precipitate is filtered off, washed with water and then dried under reduced pressure. 9.5 g of 1-(3,4-dihydroquinolin-1(2H)-ylcarbonyl)piperidine-4-carboxylic acid are obtained.
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