[CH2:1]([O:5][N:6]=[C:7]([C:13](=O)[CH2:14]Cl)[C:8]([O:10][CH2:11][CH3:12])=[O:9])[CH2:2][CH2:3][CH3:4].[NH2:17][C:18]([NH2:20])=[S:19].C([O-])(=O)C.[Na+].C(=O)([O-])[O-].[Na+].[Na+]>C(O)C.O>[NH2:20][C:18]1[S:19][CH:14]=[C:13]([C:7](=[N:6][O:5][CH2:1][CH2:2][CH2:3][CH3:4])[C:8]([O:10][CH2:11][CH3:12])=[O:9])[N:17]=1A solution of ethyl 2-n-butoxyimino-4-chloro-3-oxobutyrate (syn isomer, 52.1 g.), thiourea (15.9 g.), sodium acetate 3 hydrate (28.4 g.), water (130 ml.) and ethanol (180 ml.) was stirred at 40° C. for 1.25 hours. The resultant solution was adjusted to pH 6.5 with an aqueous solution of sodium carbonate under ice cooling, and stirred for 20 minutes under ice cooling. The precipitates were collected by filtration, and washed with water and diisopropyl ether in turn to give ethyl 2-(2-aminothiazol-4-yl)-2-n-butoxyiminoacetate (syn isomer, 36.1 g.), mp 126° to 128° C.
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