To a solution of (S)-4′-fluoro-2′-methoxy-5,6-dihydrospiro[[1,3]thiazine-4,9′-xanthene]-2,7′-diamine (55 mg, 0.159 mmol), 5-chloro-2-pyridinecarboxylic acid (37.6 mg, 0.239 mmol), and TEA (0.067 mL, 0.478 mmol) in DCM (1.5 mL) was added propylphosphonic anhydride solution, 50 wt. % in ethyl acetate (0.152 mL, 0.239 mmol). The mixture was stirred at rt. 0.5 hr later, the reaction mixture was concentrated. The red residue was diluted with water and extracted with DCM. The organic extract was washed with brine and dried over MgSO4. The solution was filtered and concentrated in vacuo to give the crude material as a red solid. The crude material was purified by chromatography eluting with a gradient of DCM for 5 mins and 25% to 35% to 50% DCM/MeOH/NH4OH in (40% of EtOAc in Heptane), to provide (S)—N-(2-amino-4′-fluoro-2′-methoxy-5,6-dihydrospiro[[1,3]thiazine-4,9′-xanthen]-7′-yl)-5-chloropicolinamide (11 mg, 0.023 mmol, 14.24% yield) as off-white solid.
