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 (R)-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 minutes 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 reaction mixture was then concentrated and diluted with MeOH. The crude product was purified by 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-(D-alanylamino)cyclohexyl)amino)-N-(2-fluoro-4-pyridinyl)-8-(2-pyridinylamino)imidazo[1,2-b]pyridazine-3-carboxamide (11.5 mg, 0.022 mmol, 41.9% yield) as a white solid. HPLC Rt=1.613 (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.
