[F:1][C:2]([F:11])([F:10])[C:3]([NH:5][CH2:6][C:7]([OH:9])=[O:8])=[O:4].[CH2:12](Br)/[CH:13]=[CH:14]/[CH3:15].C1CCN2C(=NCCC2)CC1>CN(C=O)C>[F:1][C:2]([F:10])([F:11])[C:3]([NH:5][CH2:6][C:7]([O:9][CH2:12]/[CH:13]=[CH:14]/[CH3:15])=[O:8])=[O:4]A mixture of 143.1 g (836 mmol) of N-trifluoroacetylglycine in 1 L of DMF is chilled to −8° C. as 100 mL (844 mmol) of E-crotyl bromide is added dropwise, followed by addition of 140 mL (937 mmol) of DBU at −5° C. After 1.5 h at −5° C. and 2 h at −2° C. the mixture is allowed to warm to 25° C. The mixture is cooled to 0° C. and 40 mL more DBU is added. After warming to 25° C. the mixture is concentrated in vacuo. 1 L of 1:1 ether-water is added. The organic layer is separated, washed with water, 1 N HCl, saturated aqueous sodium bicarbonate, and saturated aqueous sodium chloride. Drying and concentration in vacuo is followed by trituration of the oil with hexanes-EtOAC to provide a solid. Chromatography on silica gel (elution with 3:1 hexanes-EtOAc) affords 49.96 g of (2E)-2-buten-1-yl N-trifluoroacetylglycinate as an oil.
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