5-[(4-Chloro-2-fluorophenyl){7-[(methylsulfanyl)methyl]-1H-indol-3-yl}methyl]-2,2-dimethyl-1,3-dioxane-4,6-dione → Ethyl 3-(4-chloro-2-fluorophenyl)-3-{7-[(methylsulfanyl)methyl]-1H-indol-3-yl}propanoate

5.0 mg (0.08 mmol) of copper powder were added to 3.60 g (7.79 mmol) of the compound from Example 15A in 56 ml of pyridine and 14 ml of ethanol. The reaction mixture was heated under reflux for 1 h. It was concentrated, and the residue was taken up in ethyl acetate, washed with 1N hydrochloric acid, dried over magnesium sulfate, filtered through silica gel and concentrated. The crude product was purified by preparative HPLC (RP18 column; mobile phase: acetonitrile/water gradient with addition of 0.1% formic acid) to result in 2.23 g (70% of theory) of the title compound.