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 121 mg (0.47 mmol) of the compound from Example 87A 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 35.0 mg (20% of theory) of diastereomer 1 and 31.3 mg (18% of theory) of diastereomer 2 of the title compound.
