[OH-].[Na+].[CH3:3][O:4][N:5]=[C:6]([C:12]1[N:13]=[N:14][S:15][CH:16]=1)[C:7]([O:9]CC)=[O:8]>CO>[CH3:3][O:4][N:5]=[C:6]([C:12]1[N:13]=[N:14][S:15][CH:16]=1)[C:7]([OH:9])=[O:8]1N Aqueous solution of sodium hydroxide (6.7 ml.) was added to a solution of ethyl 2-methoxyimino-2-(1,2,3-thiadiazol-4-yl)acetate (syn isomer) (1.2 g.) in methanol (10 ml.) and the mixture was stirred for 1.5 hours at ambient temperature. Methanol was distilled off from the reaction mixture and water was added to the residue. The mixture was washed with ether, adjusted to pH 1 with 10% hydrochloric acid and extracted with ethyl acetate. The extract was washed with a saturated aqueous solution of sodium chloride and dried over magnesium sulfate. The solvent was distilled off to give prisms of 2-methoxyimino-2-(1,2,3-thiadiazol-4-yl)acetic acid (syn isomer) (0.7 g.), m.p. 110° to 113° C.
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