Br[CH2:2][C:3](=O)[C:4]([O:6][CH2:7][CH3:8])=[O:5].[C:10](=[S:15])([NH2:14])[CH2:11][CH2:12][CH3:13]>C(O)C>[CH2:11]([C:10]1[S:15][CH:2]=[C:3]([C:4]([O:6][CH2:7][CH3:8])=[O:5])[N:14]=1)[CH2:12][CH3:13]Ethyl 3-bromo-2-oxopropanoate (6.32 mL) was added to a solution of butanethioamide (example 87, step a) (5.2 g) in ethanol (100 mL) and the resulting mixture heated at reflux overnight. The solvent was evaporated and the residue partitioned between ethyl acetate (100 mL) and saturated sodium hydrogen carbonate solution (100 mL). The layers were separated and the aqueous phase extracted with ethyl acetate (2×100 mL). The combined organic solutions were washed with brine (100 mL) dried over sodium sulphate, filtered and evaporated. Purification was by silica gel chromatography eluting with 10:1 isohexane:ethyl acetate. The fractions containing product were combined and evaporated to give the subtitled compound as a yellow oil. Yield 5.24 g.
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