Methyl 6-bromo-1-oxo-4-phenyl-1H-isochromene-3-carboxylate (0.319 g, prepared according to the reported preparation in US 2005/0148624) and the compound prepared in Example 9 (0.458 g) were suspended in methanol (10 mL) and diisopropylethylamine (0.772 mL) was added. Tetrahydrofuran (5 mL) was added and the reaction mixture was heated at 60° C. overnight. The reaction mixture was then cooled to room temperature and concentrated. The reaction mixture was partitioned between ethyl acetate and a saturated aqueous sodium bicarbonate solution. The organics were washed with brine, dried over anhydrous magnesium sulfate and concentrated. The residue was purified by column chromatography on silica gel (ethyl acetate) to obtain the title compound (0.560 g) having the following physical data.
