C[O:2][C:3](=[O:18])[CH:4]([N:11]1[C:16](=[O:17])[CH:15]=[CH:14][CH:13]=[N:12]1)[CH2:5][CH:6]1[CH2:10][CH2:9][CH2:8][CH2:7]1.[OH-].[Na+]>CO>[CH:6]1([CH2:5][CH:4]([N:11]2[C:16](=[O:17])[CH:15]=[CH:14][CH:13]=[N:12]2)[C:3]([OH:18])=[O:2])[CH2:10][CH2:9][CH2:8][CH2:7]1A solution of 3-cyclopentyl-2-(6-oxo-6H-pyridazin-1-yl)-propionic acid methyl ester (2.99 g, 11.97 mmol) in methanol (7.9 mL, 1.5M) was treated with a 4N aqueous sodium hydroxide solution (3.29 mL, 13.16 mmol) and stirred at 25° C. overnight. At this time, the reaction was concentrated in vacuo. The residue was partitioned between water (100 mL) which was acidified with a 2N aqueous hydrochloric acid solution and a solution of 90/10 methylene chloride/methanol (3×75 mL). The combined organics were dried over sodium sulfate, filtered and concentrated in vacuo to afford 3-cyclopentyl-2-(6-oxo-6H-pyridazin-1-yl)-propionic acid (2.45 g, 86%) as a light pink solid; ES+-HRMS m/e calcd for C12H16N2O3 [M+H+] 237.1234, found 237.1233.
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