A mixture of chloromethyl butyrate (20.5 μL, 164 μmol) and NaI (24.5 mg, 164 μmol) in acetone (2.0 mL, 27 mmol) was stirred at 60° C. for 1 hour, then cooled to room temperature and added to a mixture of (R)-3-[N-(3′-chlorobiphenyl-4-ylmethyl)-N′-(3-hydroxyisoxazole-5-carbonyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl ester (30.0 mg, 54.5 μmol) and Et3N (38.0 μL, 273 μmol) in acetone (1 mL). The resulting mixture was stirred at room temperature for 2 hours, concentrated, dissolved in AcOH (2 mL), filtered, and purified by reverse phase preparative HPLC. The desired fractions were combined and lyophilized. Zinc (178 mg, 2.7 mmol) and AcOH (1.0 mL, 18 mmol) was added and the resulting mixture was stirred at room temperature for 2 hours. The mixture was filtered and purified by reverse phase preparative HPLC to yield the title compound (2.5 mg). MS m/z [M+H]+ calc'd for C25H26ClN3O8, 532.14. found 532.2.
