A mixture of chloromethyl ethyl carbonate (17.9 mg, 129 μmol) and NaI (19.4 mg, 129 μmol) in acetone (0.7 mL, 10 mmol) was heated at 65° C. for 1 hour. The mixture was then cooled to room temperature and a mixture of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-(3-methoxyisoxazole-5-carbonyl)hydrazino]-2-hydroxypropionic acid (20.0 mg) and DIPEA (15.0 μL, 0.1 mmol) in acetone (0.3 mL) was added. The resulting mixture was stirred at room temperature for 1 hour then concentrated. The residue was dissolved in AcOH (2.0 mL), filtered, and purified by reverse phase preparative HPLC. The desired fractions were combined and freeze dried to yield a white solid. The solid was dissolved in acetic acid (1.5 mL), filtered and purified by reverse phase preparative HPLC to yield the title compound (5.8 mg, purity 94%). MS m/z [M+H]+ calc'd for C25H25ClFN3O9, 566.13. found 566.
