O[N:2]=[C:3]([C:13]1[S:14][CH:15]=[CH:16][CH:17]=1)[CH:4]([CH3:12])[C:5](=[O:11])[C:6]([O:8][CH2:9][CH3:10])=[O:7].S(=O)(=O)(O)O.C(=O)(O)[O-].[Na+]>C(O)C>[CH3:12][C:4]1[C:3]([C:13]2[S:14][CH:15]=[CH:16][CH:17]=2)=[N:2][O:11][C:5]=1[C:6]([O:8][CH2:9][CH3:10])=[O:7]Ethyl 4-(hydroxyimino)-3-methyl-2-oxo-4-(thiophen-2-yl)butanoate (7.7 g, 30.2 mmol) and concentrated sulfuric acid (8 mL) were added to 120 mL of absolute ethanol and the mixture was refluxed for 20 hours. After the mixture cooled to room temperature, saturated sodium bicarbonate solution was added to neutralize the mixture. The product was extracted with EtOAc and the combined organic layer was dried over MgSO4 and concentrated to give 3.9 g of the title compound. MS: (+) m/z 238.38 (M+1).
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