To a solution of N-(3-ethyl-1-((6-methylpyridin-2-yl)methyl)-1H-indazol-4-yl)-7-(piperazine-1-carbonyl)imidazo[1,2-a]pyridine-3-carboxamide dihydrochloride (Example 12; 5 mg, 0.0084 mmol) in dichloromethane/methanol (1:1; 1 mL) was added an excess of sodium triacetoxyborohydride and formaldehyde solution. The mixture was stirred at ambient temperature for 2 hours. Further excess sodium triacetoxyborohydride and formaldehyde solution were added and the mixture was stirred an additional 0.5 hours. The mixture was concentrated under a stream of nitrogen and the residue was purified using preparative thin layer chromatography on silica, eluting with 15% methanol and 0.5% ammonium hydroxide in dichloromethane to provide the desired product (free base form). This material was dissolved in methanol and filtered. To the filtrate was added hydrogen chloride (1 mL; 2M in ether) and the solvent was evaporated to a residual film under a stream of nitrogen. The material was dried under high vacuum to give N-(3-ethyl-1-((6-methylpyridin-2-yl)methyl)-1H-indazol-4-yl)-7-(4-methylpiperazine-1-carbonyl)imidazo[1,2-a]pyridine-3-carboxamide dihydrochloride (3.3 mg). MS (APCI), positive scan, m/z=537.3 (M+H).
