[CH3:1][O:2][C:3](=[O:8])/[CH:4]=[C:5](/[O-:7])\[CH3:6].[Na+].[I-].[K+].[CH2:12](Br)[CH2:13][CH2:14][CH3:15]>CN1CCCN(C)C1=O>[C:5]([CH:4]([CH2:12][CH2:13][CH2:14][CH3:15])[C:3]([O:2][CH3:1])=[O:8])(=[O:7])[CH3:6]30 g (217 mmol) of sodium (2E)-4-methoxy-4-oxo-2-buten-2-olate (Example 13A) suspended in 1,3-dimethyltetrahydro-2(1H)-pyrimidone and 1.24 g (7.5 mmol) of potassium iodide are treated dropwise with 29.8 g (217 mmol) of butyl bromide and the mixture is stirred at 80° C. for 1 h under reflux. The cooled mixture is then added to ice water and extracted with diethyl ether. The ether phase is washed with sodium thiosulphate solution, dried, concentrated and chromatographed. The eluent used is cyclohexane having an increasing ethyl acetate content.
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