50 mg (0.12 mmol) of the compound from example 121 were initially charged in tetrahydrofuran (5 ml), then 0.11 ml (0.81 mmol) of isoamyl nitrite and 3 mg (0.02 mmol) of copper(II) chloride were added, and the mixture was stirred at RT overnight. The reaction mixture was admixed with saturated aqueous sodium hydrogencarbonate solution and extracted twice with ethyl acetate. The collected organic phases were dried over sodium sulfate, filtered and concentrated. The residue was purified by means of preparative HPLC (eluent: acetonitrile/water with 0.1% formic acid gradient). This gave 7 mg (13% of theory) of the title compound in solid form.
