563 mg (1.305 mmol) of the compound obtained in Example 15A were initially charged in 1,2-dimethoxyethane (7.5 ml), and 339 mg (1.305 mmol) of caesium iodide, 165 mg (0.652 mmol) of iodine and 74 mg (0.391 mmol) of copper(I) iodide were then added. Isopentyl nitrite (1.04 ml) was then added, and the mixture was heated at 60° C. for 2 days. After cooling, the mixture was filtered, the filter cake was washed with ethyl acetate and the filtrate was washed twice with 5% strength aqueous sodium thiosulphate solution and once with saturated aqueous sodium chloride solution. The organic phase was then dried over sodium sulphate, filtered and concentrated to dryness. The residue was purified by preparative HPLC (acetonitrile/water (+0.05% formic acid) gradient). This gave 98 mg of the title compound (14% of theory).
