Triethylamine (0.0967 mL, 0.695 mmol) was added to a slurry of (rac)-2-amino-4-(3-fluoro-4-(5-(1-phenylcyclopropyl)thiazolo[5,4-b]pyridin-2-yl)phenyl)butanoic acid hydrochloride (0.153 g, 0.316 mmol) in THF (5.00 mL, 61.7 mmol) and WATER (5.00 mL, 278 mmol). The reaction mixture was cooled in an ice bath, and a solution of Boc2O (0.117 g, 0.537 mmol) in THF 2 mL was added dropwise, and the solution was then stirred at ambient temperature for 18 h. The reaction mixture was diluted with water and EtOAc, pH was adjusted to 5 with 1 N aq. HCl, and the aqueous layer was extracted with EtOAc. The combined organics were dried over MgSO4, filtered, and concentrated in vacuo, and the residue purified by chiral SFC (Column: Chiralpak AS-H (21×250 mm, 5 um); A: Liquid CO2; B: Methanol; Isocratic: 70:30 (A:B); Flow Rate: 70 mL/min) to give separately (R)-2-(tert-butoxycarbonylamino)-4-(3-fluoro-4-(5-(1-phenylcyclopropyl)-thiazolo[5,4-b]pyridin-2-yl)phenyl)butanoic acid and (S)-2-(tert-butoxycarbonylamino)-4-(3-fluoro-4-(5-(1-phenylcyclopropyl)thiazolo[5,4-b]pyridin-2-yl)phenyl)butanoic acid. MS (ESI) m/z: calculated: 547.2; Observed: 548.1 (M++1).
