C(OC([N:8]1[CH2:13][CH2:12][C:11]([C:15]2[CH:20]=[CH:19][C:18]([F:21])=[CH:17][C:16]=2[F:22])(O)[CH2:10][CH2:9]1)=O)(C)(C)C.S(=O)(=O)(O)O.[OH-].[Na+]>C1(C)C=CC=CC=1>[F:22][C:16]1[CH:17]=[C:18]([F:21])[CH:19]=[CH:20][C:15]=1[C:11]1[CH2:12][CH2:13][NH:8][CH2:9][CH:10]=14-(2,4-Difluoro-phenyl)-4-hydroxy-piperidine-1-carboxylic acid tert-butyl ester (0.4 g) was dissolved in toluene (10 mL). Concentrated sulphuric acid (0.3 mL) was added and the mixture was heated at reflux for 2 hours and then allowed to stand at room temperature overnight. A solution of aqueous sodium hydroxide (1 N, 30 mL) was added and the products extracted into ethyl acetate. The organic solution was dried with magnesium sulphate, filtered and the solvent removed by evaporation under vacuum to give the title compound as a dark oil (0.2 g) which was used without further purification. LCMS m/z 196.1 [M+H]+. R.T.=2.12 min (Analytical Method 4).
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