C([CH:3]([C:7]([NH2:9])=[O:8])[C:4]([O-:6])=[O:5])C.C(O[CH:13]=[C:14]([C:20]([C:22]([O:24][CH2:25][CH3:26])=[O:23])=O)[C:15]([O:17][CH2:18][CH3:19])=[O:16])C.[C:27]([O-])(=O)[CH3:28].[Na+]>C(O)C>[CH2:25]([O:24][C:22]([C:20]1[NH:9][C:7](=[O:8])[C:3]([C:4]([O:6][CH2:27][CH3:28])=[O:5])=[CH:13][C:14]=1[C:15]([O:17][CH2:18][CH3:19])=[O:16])=[O:23])[CH3:26]A solution of ethylmalonamate (23.6 g, 0.18 mol) in absolute ethanol (300 mL) is added to a stirred solution of diethyl ethoxymethyleneoxalacetate (44.0 g, 0.18 mol) in ethanol (200 mL) at 0° C., followed by the addition, of solid sodium acetate (14.72 g, 0.18 mol). After stirring for ten minutes at 0° C., the mixture is heated to reflux and stirred for 13.5 hours. After cooling, the ethanol is removed under vacuum, and the residue diluted with water and acidified to pH 2 with concentrated hydrochloric acid. The aqueous solution is extracted with methylene chloride (2×200 mL) and the organic layer washed with 300 mL saturated sodium chloride, then dried over anhydrous magnesium sulfate and concentrated in vacuum to give 45.0 g of the title product as an orange oil.
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