A solution of 3-cyclopentyl-2-(6-oxo-6H-pyridazin-1-yl)-propionic acid (183 mg, 0.77 mmol) in methylene chloride (4.30 mL, 0.18M) at 25° C. was treated with N,N,N′,N′-tetramethyl-O—(N-succinimidyl)uronium tetrafluoroborate (0.28 g, 0.92 mmol) and N,N-diisopropylethylamine (0.40 mL, 2.32 mmol). The resulting solution was stirred at 25° C. for 2 h. After this time, the reaction was treated with 1-(3-amino-pyrazol-1-yl)-2-methyl-propan-2-ol (Intermediate 1, 156 mg, 1.0 mmol). The resulting solution was stirred at 25° C. for 2 d. After this time, the reaction was partitioned between water (75 mL) and methylene chloride (3×75 mL). The combined organics were dried over sodium sulfate, filtered and concentrated in vacuo. Silica gel column chromatography (ISCO, 40 g, 1-2% methanol/methylene chloride) afforded 3-cyclopentyl-N-[1-(2-hydroxy-2-methyl-propyl)-1H-pyrazol-3-yl]-2-(6-oxo-6H-pyridazin-1-yl)-propionamide as an off-white solid (21.9 mg, 7.6%); ES+-HRMS m/e calcd for C19H27N5O3 [M+H+] 374.2187 found 374.2187. 1H-NMR (300 MHz, DMSO-d6) δ ppm 0.99-1.72 (m, 9H), 1.05 (s, 3H), 1.06 (s, 3H), 1.92 (m, 1H, CH), 2.28 (m, 1H), 3.89 (s, 2H), 4.67 (s, 1H), 5.52 (dd, J=4.2, J=10.6 Hz, 1H), 6.39 (d, J=2.3 Hz, 1H), 6.94 (dd, Jo=9.4 Hz, Jm=1.5 Hz, 1H), 7.42 (dd, Jo=9.4, Jo=3.8 Hz, 1H), 7.52 (d, J=2.3 Hz, 1H), 8.00 (dd, Jo=3.8 Hz, Jm=1.5 Hz, 1H), 10.79 (s, 1H).
