Into a 25-mL round-bottom flask, was placed (R)-methyl 2-phenyl-3-(2-(trifluoromethyl)pyrrolidin-1-yl)quinoxaline-6-carboxylate (40 mg, 0.10 mmol, 1.00 equiv), sodium hydroxide (20 mg, 0.50 mmol, 5.00 equiv), methanol (5 mL), water (1 mL). The resulting solution was stirred for 5 hs at 50° C. in an oil bath. The resulting mixture was concentrated under vacuum. The residue was diluted in 5 mL of water. The PH value was aqueous solution was adjusted to 4 with aq hydrochloric acid (1N). The resulting solids were collected by filtration. The crude product (50 mg) was purified by Prep-HPLC with the following conditions (1#-Waters 2767-1): Column, SunFire Prep C18, 5 um, 19*150 mm; mobile phase, water with 0.05% TFA and CH3CN (60% CH3CN up to 90% in 8 min, up to 100% in 1.5 min); Detector, UV 220 254 nm. This resulted in 12 mg (30%) of (R)-2-phenyl-3-(2-(trifluoromethyl)pyrrolidin-1-yl)quinoxaline-6-carboxylic acid as a yellow solid.
