A suspension of N-(7′-bromo-4′-fluoro-2′-methoxy-5,6-dihydrospiro[[1,3]oxazine-4,9′-xanthene]-2-yl)-4-nitrobenzamide (6.0 g, 11.06 mmol) in methanol (60 mL) was heated to 65° C. NaOH (2 M solution) (48.7 ml, 97 mmol) was added and the resulting mixture was heated to 65° C. for 4 hrs. The reaction mixture was concentrated under reduced pressure, the precipitate was filtered off, washed twice with water and dried to afford 7′-bromo-4′-fluoro-2′-methoxy-5,6-dihydrospiro[[1,3]oxazine-4,9′-xanthen]-2-amine (3.90 g, 9.92 mmol, 50.9% yield) as white solid.
