[CH3:1][N:2]1[C:6]([CH:7]2[CH2:12][CH:11]([C:13]([O:15]CC)=[O:14])[CH2:10][CH2:9][N:8]2[C:18]([O:20][CH2:21][C:22]2[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=2)=[O:19])=[N:5][N:4]=[N:3]1.[Li+].[OH-].Cl>C1COCC1.O>[CH2:21]([O:20][C:18]([N:8]1[CH2:9][CH2:10][CH:11]([C:13]([OH:15])=[O:14])[CH2:12][CH:7]1[C:6]1[N:2]([CH3:1])[N:3]=[N:4][N:5]=1)=[O:19])[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=11-Benzyl 4-ethyl 2-(1-methyl-1H-tetrazol-5-yl)piperidine-1,4-dicarboxylate (1.14 g, 2.93 mmol) (from reference compound 36, step 6) was dissolved in THF (10 mL) and water (10 mL) and LiOH (0.280 g, 11.69 mmol) was added. The mixture was stirred at room temperature for 30 min and then diluted with water and acidified with 2 M HCl. The aqueous phase was extracted 3 times with EtOAc, the combined organic phase dried over Na2SO4 and evaporated to yield 1-(Benzyloxycarbonyl)-2-(1-methyl-1H-tetrazol-5-yl)piperidine-4-carboxylic acid (990 mg, 98%). 1H NMR (400 MHz, cdcl3) δ 1.89-2.01 (m, 1H), 2.15-2.24 (m, 1H), 2.27-2.36 (m, 1H), 2.50-2.61 (m, 1H), 2.78 (p, 1H), 3.68-3.80 (m, 1H), 3.91-4.09 (m, 4H), 5.08 (q, 2H), 5.44 (t, 1H), 7.23-7.39 (m, 5H). MS m/z 346 (M+H)+
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