[F:1][C:2]1[CH:3]=[CH:4][C:5]([NH:8][NH2:9])=[N:6][CH:7]=1.[C:10](O)(=[O:14])[CH:11]([CH3:13])[CH3:12].C1C=C2N=NN(O)C2=CC=1.O.C(Cl)CCl.C([O-])(O)=O.[Na+]>C(Cl)Cl.CCOCC>[F:1][C:2]1[CH:3]=[CH:4][C:5]([NH:8][NH:9][C:10](=[O:14])[CH:11]([CH3:13])[CH3:12])=[N:6][CH:7]=1To a solution of 5-fluoro-2-hydrazinyl-pyridine (for reference procedure see WO 2010/022076, which is incorporated herein by reference in its entirety; 2.08 g, 16.4 mmol), isobutyric acid (1.82 mL, 19.6 mmol), and HOBt hydrate (251 mg, 1.64 mmol) in DCM (50 mL), EDC (3.76 g, 19.6 mmol) was added, and the resulting orange solution was stirred at room temperature for 18 h. Sat. aq. NaHCO3 (50 mL) was added, and the mixture was stirred vigorously for 15 min. The organics were washed with sat. aq. NaHCO3 (50 mL), passed through a hydrophobic frit, and concentrated under vacuum to leave a pale brown solid. The solid was suspended in Et2O (50 mL) and filtered, washing with Et2O (25 mL), to leave a white solid (1.48 g, 46%). The ethereal washings were concentrated under vacuum and the residue suspended in Et2O (10 mL), filtered, washed with Et2O (2×2 mL), to leave a white solid (330 mg, 10%). The solids were combined (1.81 g, 56%). 1H NMR (400 MHz, CDCl3): 1.23 (6H, d), 2.50 (1H, sept), 6.65 (1H, dd), 6.80 (1H, d), 7.29 (1H, ddd), 7.77 (1H, br s), 8.01 (1H, d).
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