[N:1]1([C:6]2[N:11]=[CH:10][C:9]3[CH:12]([C:15]([O-:17])=[O:16])[CH2:13][CH2:14][C:8]=3[CH:7]=2)[CH:5]=[N:4][N:3]=[N:2]1.[OH-].[Li+]>O1CCCC1.O>[N:1]1([C:6]2[N:11]=[CH:10][C:9]3[CH:12]([C:15]([OH:17])=[O:16])[CH2:13][CH2:14][C:8]=3[CH:7]=2)[CH:5]=[N:4][N:3]=[N:2]1A solution of 3-(1H-tetrazol-1-yl)-6,7-dihydro-5H-cyclopenta[c]pyridine-7-carboxylate (235 mg, 0.958 mmol) in tetrahydrofuran (5 mL) and water (1.5 mL) at room temperature was treated with lithium hydroxide solution (1 M, 1.44 mL). After 30 min. the solution was concentrated to remove tetrahydrofuran and the remaining aqueous acidified with 1 N hydrochloric acid solution (to Ph ˜4) and extracted with ethyl acetate (3×). The combined organics were washed with brine, dried (Na2SO4), filtered and concentrated to provide 3-(1H-tetrazol-1-yl)-6,7-dihydro-5H-cyclopenta[c]pyridine-7-carboxylic acid. 1H NMR (500 MHz, CD3OD), δ 9.89 (s, 1H), 8.58 (s, 1H), 8.01 (s, 1H), 4.25 (dd, J=5.0, 5.0 Hz, 1H), 3.27-3.05 (m, 2H), 2.47-2.57 (m, 2H); LC/MS (M+1)+=232.2.
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