Sodium (3 eq) was added to ethanol under nitrogen at room temperature and stirred until complete dissolution occured. 1-(2,4-Bis-benzyloxy-5-isobutyl-phenyl)-ethanone (1 eq) was added, followed by diethyl oxalate (1.5 eq) and the reaction mixture heated to reflux for 4 hours. The mixture was allowed to cool to room temperature and acidified with 2M HCl (aq) to give a yellow precipitate of 4-(2,4-Bis-benzyloxy-5-isobutyl-phenyl)-2,4-dioxo-butyric acid ethyl ester, which was obtained by filtration.
