A solution of tert-butyl (3S)-1-(2,2,2-trifluoro-1-(6-hydrazinylpyridin-3-yl)ethyl)pyrrolidin-3-ylcarbamate (Example 1, Step D; 0.46 g, 1.03 mmol) and methyl 2-formylquinoline-7-carboxylate (0.22 g, 1.03 mmol) in EtOH (10 mL) was stirred at ambient temperature for 1 hour. The solvent was removed under reduced pressure. The residue was dissolved in DCM (10 mL) and iodo benzene diacetate (0.40 g, 1.24 mmol) was added. The mixture was stirred at ambient temperature for 1 hour. Ethyl acetate (20 mL) and saturated sodium bicarbonate (10 mL) were added. The organic layer was separated, washed with brine, dried (sodium sulfate), filtered and concentrated under reduced pressure. The residue obtained was dissolved in THF (5 mL) and 2 N LiOH (5.15 mL, 10.30 mmol) was added. The mixture was stirred at ambient temperature for 6 hours. Ether (20 mL) was added. The aqueous layer was separated and acidified with saturated potassium hydrogen sulfate to about pH 3. The resulting solid was collected by filtration to give 2-(6-(1-((S)-3-(tert-butoxycarbonylamino)pyrrolidin-1-yl)-2,2,2-trifluoroethyl)-[1,2,4]triazolo[4,3-a]pyridin-3-yl)quinoline-7-carboxylic acid (0.45 g, 78.5%) as a solid.
