[H-].[Na+].[C:3]([NH:6][CH:7]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:8]([O:10][CH2:11][CH3:12])=[O:9])(=[O:5])[CH3:4].[C:18]([O:21][CH2:22][CH2:23][CH2:24][CH2:25]Br)(=[O:20])[CH3:19]>CN(C)C=O>[C:3]([NH:6][C:7]([CH2:25][CH2:24][CH2:23][CH2:22][O:21][C:18](=[O:20])[CH3:19])([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:8]([O:10][CH2:11][CH3:12])=[O:9])(=[O:5])[CH3:4]A stirred suspension of 95% sodium hydride (60.8 g, 2.532 mol) in anhydrous dimethylformamide (500 ml) under an atmosphere of argon was cooled to 0° C. (ice bath). A solution of diethyl acetamidomalonate (500 g, 2.302 mol) in anhydrous dimethylformamide (1.2 l) was added over a period of 45 minutes while keeping the reaction temperature below 18° C. After the addition was complete, the turbid solution was gradually warmed to room temperature. After stirring for one hour at room temperature, 4-bromobutyl acetate (471.5 g, 2.417 mol) was added. The mixture was then stirred at 59°-60° C. for 18 hours. The resulting slurry was cooled to room temperature, quenched with absolute ethanol (40 ml) and glacial acetic acid (4 ml), stirred for about 15 minutes, poured into a 10% lithium chloride solution and extracted with ethyl acetate (2×3 l). The combined ethyl acetate extracts were washed with 10% lithium chloride (3×3 l), dried (anhydrous sodium sulfate), and evaporated in vacuo to give 750 g of title product as an oil.
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