To a solution of (S)-ethyl 6-(6-(3-ethylureido)-4-(4-(trifluoromethyl)thiazol-2-yl)pyridin-3-yl)-1-(1-hydroxy-3,3-dimethylbutan-2-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylate (Example 104, 212.7 mg, 0.34 mmol) in tetrahydrofuran (1 mL) and methanol (1 mL) was added 2 M lithium hydroxide (0.253 mL, 0.51 mmol). The reaction mixture was heated at 100° C. for 15 min in a microwave reactor. The reaction mixture was cooled to room temperature and diluted with water. 1 N HCl was added until pH 3-4 was reached. The precipitate that formed was collected by filtration, washed with water and hexanes. Purification via column chromatography (silica, 95:5 methylene chloride/methanol) provided (S)-6-(6-(3-ethylureido)-4-(4-(trifluoromethyl)thiazol-2-yl)pyridin-3-yl)-1-(1-hydroxy-3,3-dimethylbutan-2-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid as a light yellow solid (72.3 mg, 35%).
