(6-(5-Methoxy-1-methyl-1H-indol-3-yl)-5-((2-(trimethylsilyl)ethoxy)methyl)-5H-pyrrolo[2,3-b]pyrazin-2-yl)methanamine (0.185 g, 0.423 mmol, Preparation #I.1) in THF (5 mL) was treated with pyridine (0.044 mL, 0.55 mmol) and Ac2O (0.044 mL, 0.46 mmol). After about 5 min the mixture was treated with AcOH (0.024 mL, 0.42 mmol), diluted with EtOAc (20 mL) and then washed with water (15 mL) and brine (10 mL). The organic layer was dried over anhydrous MgSO4, filtered and evaporated under reduced pressure to give N-((6-(5-Methoxy-1-methyl-1H-indol-3-yl)-5-((2-(trimethylsilyl)ethoxy)methyl)-5H-pyrrolo[2,3-b]pyrazin-2-yl)methyl)acetamide (0.207 g, 102%, crude): LC/MS (Table 2, Method a) Rt=2.63 min; MS m/z 480 (M+H)+.
