2-Hydroxy-2-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)phenyl)acetic acid (Int-Va, 90 mg, 0.209 mmol) was dissolved in DMF (1 mL) prior to the addition of 4-methylmorpholine (115 μL, 1.043 mmol), 3-amino-azetidine-1-carboxylic acid tert-butyl ester (53.9 mg, 0.313 mmol), and BOP (166 mg, 0.376 mmol). This was stirred overnight before EtOAc was added. The solution was washed with brine, 1N HCl, and sat. NaHCO3 solution. The organic layer was dried and concentrated to give single enantiomer tert-butyl 3-(2-hydroxy-2-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)phenyl)acetamido)azetidine-1-carboxylate (120.6 mg, 0.206 mmol, 99% yield): LCMS=586.4 [M+H]+. A portion of this tert-butyl 3-(2-hydroxy-2-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)phenyl)acetamido)azetidine-1-carboxylate (118 mg, 0.202 mmol) was dissolved in CH2Cl2 (2 mL) and TFA (2 mL). This was stirred for 1 h and then concentrated. The resulting residue was purified by preparative HPLC (PHENOMENEX® Luna 5u C18 21.2×100 mm, gradient elution with Method 1—MeOH/water containing 0.1% trifluoroacetic acid as defined above, 0% B to 100% B% over 10 min, product retention time=10.5 min, 20 mL/min, 220 nM) to give single enantiomer N-(azetidin-3-yl)-2-hydroxy-2-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)phenyl)acetamide-TFA (30 mg, 0.046 mmol, 22.60% yield): LCMS=486.0 [M+H]+; 1H NMR (400 MHz, methanol-d4) δ ppm 8.14-8.25 (2 H, m), 7.65-7.78 (4 H, m), 7.54-7.65 (3 H, m), 5.18 (1 H, s), 4.71 (1 H, t, J=7.81 Hz), 4.16-4.32 (4 H, m). HPLC Peak RT=8.3 min (Analytical Method A).
