C([O-])C.[Na+].[CH3:5][C:6]([CH3:12])([CH3:11])[CH2:7][C:8](=[O:10])[CH3:9].[CH2:13]([O:15][C:16](=[O:22])[C:17](OCC)=[O:18])[CH3:14].Cl>CCO.O>[CH2:13]([O:15][C:16](=[O:22])/[C:17](/[OH:18])=[CH:9]/[C:8](=[O:10])[CH2:7][C:6]([CH3:12])([CH3:11])[CH3:5])[CH3:14]To an ice-cooled solution of sodium ethanolate (128.5 g, 1.79 mol) in EtOH (2500 ml) under nitrogen atmosphere is added 4,4-dimethyl-pentan-2-one (195.0 g, 1.71 mol). Half an hour later, oxalic acid diethyl ester (231.5 g, 1.71 mol) is added. After being stirred at rt for 24 h, the reaction mixture is diluted with water, and acidified to pH 2.0 by 6N aq hydrochloric acid. The mixture is contracted to about 1 L and extracted with DCM. The combined extracts are washed with brine, dried over sodium sulfate, and concentrated in vacuo to yield the product as a brown liquid.
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