104 mg (0.47 mmol) of indium(III) chloride and 0.05 ml (0.70 mmol) of trifluoroacetic acid were added to 93.0 mg (0.39 mmol) of the compound from Example 163A and 112 mg (0.47 mmol) of the compound from Example 86A with a purity of 88% under argon in 5 ml of 1,2-dichloroethane, and the mixture was heated under reflux for 2 h. Addition of the reaction mixture to saturated aqueous ammonium chloride solution was followed by extraction with dichloromethane, drying over magnesium sulfate, filtration and concentration. The residue was purified by preparative HPLC (RP18 column; mobile phase: acetonitrile/water gradient with addition of 0.1% formic acid) to result in 30.5 mg (18% of theory) of diastereomer 1 and 28.0 mg (17% of theory) of diastereomer 2 of the title compound.
