C[O:2][C:3]([C:5]1[CH:10]=[CH:9][C:8]([C:11]#[C:12][C:13]2[CH:18]=[CH:17][CH:16]=[C:15]([F:19])[CH:14]=2)=[CH:7][N:6]=1)=[O:4].O.[Li+].[OH-].Cl>C1COCC1>[F:19][C:15]1[CH:14]=[C:13]([C:12]#[C:11][C:8]2[CH:9]=[CH:10][C:5]([C:3]([OH:4])=[O:2])=[N:6][CH:7]=2)[CH:18]=[CH:17][CH:16]=1(1.9 g, 7.44 mmol) 5-(3-Fluoro-phenylethynyl)-pyridine-2-carboxylic acid methyl ester (Example 1, step 1) was dissolved in THF (30 ml) and water (30 ml) and LiOH (357 mg, 24.9 mmol, 2 equiv.) was added at room temperature. The mixture was stirred for 16 hours at room temperature. The reaction mixture was acidified with 4N HCl to pH 2.5 and THF was evaporated to form a yellow suspension. The suspension was cooled to 0-5° C. and filtered. The crystals were washed with cold water and evaporated to dryness. The desired 5-(3-fluoro-phenylethynyl)-pyridine-2-carboxylic acid (1.71 g, 95% yield) was obtained as a light yellow solid, MS: m/e=239.9 (M+H+).
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