To a solution of (S)-methyl 2-(1H-indazol-5-yl)-3-(2-methyl-4-(pyridin-2-yl)piperazin-1-yl)quinoxaline-6-carboxylate (47 mg, 0.10 mmol) in methanol (15 ml) was added NaOH (15.6 mg, 0.39 mmol) and water (1 mL). After stirring 6 h at room temperature, the reaction mixture was concentrated under reduced pressure to afford a residue, which was dissolved in water (10 ml), adjusted to pH 6 with HCl (3N). The solids were filtered to give (S)-2-(1H-indazol-5-yl)-3-(2-methyl-4-(pyridin-2-yl)piperazin-1-yl)quinoxaline-6-carboxylic acid as a yellow solid (40 mg, 88%).
