To a solution of 2-(4-Methoxymethoxy-thianthren-1-yl)-6-morpholin-4-yl-pyran-4-one (1.1 g, 2.42 mmol) in acetone (50 ml) was added sodium iodide (0.40 g, 2.66 mmol) and concentrated HCl (3 ml). The dark suspension was stirred at room temperature for 72 hours before the careful addition of 1M sodium hydroxide solution until pH 12 was attained. The mixture was washed with EtOAc (2×50 ml) and then acidified with concentrated HCl until pH 1 whereupon a brown precipitate formed which was filtered off (0.90 g, 90%) and corresponded to the title compound. m/z (LC-MS, ESP): RT=4.39 min, (M++1)=456
