900 mg (1.89 mmol) of the compound from Example 72A and 1.36 g (9.49 mmol) of 1-bromo-2-chloroethane are dissolved in 30 ml of 1-methyl-2-pyrrolidone. 1.55 g (4.75 mmol) of caesium carbonate are added to the solution, and the mixture is stirred at 60° C. for 15 hours. Water is then added, and, after phase separation, the aqueous phase is extracted three times with tert-butyl methyl ether and three times with dichloromethane. The combined organic phases are washed successively with 1N aqueous sodium hydroxide solution and saturated sodium chloride solution and then dried over sodium sulphate. The drying agent is filtered off and the solvent is removed completely on a rotary evaporator. The residue is purified by chromatography on silica gel (cyclohexane/ethyl acetate 1:5). This gives 464 mg (45% of theory, purity according to LC-MS 74%) of the desired product.
