BOP (68.4 mg, 0.155 mmol) was added to a solution of 62B (30.0 mg, 0.052 mmol), DIEA (0.036 mL, 0.206 mmol) and (S)-2-(tert-butoxycarbonylamino)propanoic acid (19.52 mg, 0.103 mmol) in DCM (1 mL). The clear reaction mixture was stirred at room temperature for 30 min, and then concentrated to dryness. TFA (0.238 mL, 3.09 mmol) was added and the reaction solution was stirred at 70° C. for 1 h. The resulting mixture was concentrated and then diluted with MeOH and purified by preparative HPLC (Phenomenex Axia Luna 5 micron 30×100 mm) 10% B (Solvent B=90% MeOH-10% H2O-0.1% TFA) to 90% B in A (Solvent A=10% MeOH-90% H2O-0.1% TFA) to afford 6-((trans-4-(L-alanylamino)cyclohexyl)amino)-N-(2-fluoro-4-pyridinyl)-8-(2-pyridinylamino)imidazo[1,2-b]pyridazine-3-carboxamide (13.7 mg, 0.026 mmol, 49.9% yield) as white solid. HPLC Rt=1.618 minutes (Phenomenex Luna 5 micron C18 4.6×30 mm: 0 to 100 B in 2 min with 1 min hold time, Flow rate=5 mL/min, detection at 254 nm, Solvent A: 10% methanol/90% water/0.1% TFA; Solvent B: 10% water/90% methanol/0.1% TFA). [M+H]=533.17.
