(+/−)-2-((2-chloro-5-cyano-3-((4aR,8aR)-hexahydro-1H-pyrido[3,4-b][1,4]oxazin-6(7H)-yl)phenyl)amino)-4-(ethylamino)imidazo[2,1-f][1,2,4]triazine-7-carbonitrile (Example 371)(13 mg, 0.027 mmol) was taken up in MeOH (0.5 mL) and THF (0.5 mL) and trimethyl orthoformate (0.225 mL, 2.036 mmol), AcOH (6.22 μl, 0.109 mmol), and formaldehyde (2.492 μl, 0.027 mmol) were added. The reaction was stirred at 25° C. for 5 min, then NaCNBH4 (0.271 mL, 0.271 mmol) was added and the reaction stirred at 25° C. 1 hr. The reaction mixture was diluted with EtOAc and washed with sat'd NaHCO3, then brine. The organic layer was dried over Na2SO4, and concentrated. The crude material was purified via preparative LC/MS with the following conditions: Column: Waters XBridge C18, 19×200 mm, 5-μm particles; Guard Column: Waters XBridge C18, 19×10 mm, 5-μm particles; Mobile Phase A: water with 20-mM ammonium acetate; Mobile Phase B: 95:5 acetonitrile: water with 20-mM ammonium acetate; Gradient: 50-100% B over 15 minutes, then a 5-minute hold at 100% B; Flow: 20 mL/min. Fractions containing the desired product were combined and dried via centrifugal evaporation to afford (+/−)-2-((2-chloro-5-cyano-3-((4aR,8aR)-1-methylhexahydro-1H-pyrido[3,4-b][1,4]oxazin-6(7H)-yl)phenyl)amino)-4-(ethylamino)imidazo[2,1-f][1,2,4]triazine-7-carbonitrile (12.2 mg).
