Under an argon atmosphere, 0.49 mmol of the compound obtained in Step B, 0.2 mmol of tetrakis(triphenylphosphine)palladium(0) and 0.49 mmol of potassium acetate in 15 ml of DMF are heated at 140° C. for 3 hours. After returning to room temperature, the reaction mixture is filtered using a Büchner funnel and then evaporated to dryness. The residue is then hydrolysed and subsequently extracted with ethyl acetate. The organic phase is dried over magnesium sulphate and concentrated, and the residue is purified by flash chromatography over silica gel (eluant:petroleum ether/ethyl acetate) to yield the title compound.
