[C:1]([O:8][CH2:9][CH3:10])(=[O:7])[C:2]([O:4]CC)=O.[O-:11]CC.[K+].[CH3:15][C:16]([C:18]1[CH:23]=[CH:22][C:21]([O:24][CH2:25][C:26]2[CH:31]=[CH:30][CH:29]=[CH:28][CH:27]=2)=[CH:20][CH:19]=1)=O.Cl>CCOCC>[CH2:25]([O:24][C:21]1[CH:22]=[CH:23][C:18]([CH:16]([CH:15]=[O:11])[C:2](=[O:4])[C:1]([O:8][CH2:9][CH3:10])=[O:7])=[CH:19][CH:20]=1)[C:26]1[CH:31]=[CH:30][CH:29]=[CH:28][CH:27]=1Diethyl oxalate (17.7 g) is added in one portion to a stirred suspension of potassium ethoxide (10.2 g) in anhydrous ether (1000 mL). The stirred mixture is cooled to 0° C., treated with 4-benzyloxyacetophenone (25 g) portionwise, and stirring continued for 3 hours. After standing at room temperature for 18 hours the reaction mixture is poured onto 1 N hydrochloric acid (500 mL) and the organic phase separated. The organic phase is washed with water, dried over magnesium sulphate and evaporated to give ethyl 4-benzyloxypheyl-2,4-dioxobutanoate (35 g).
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