Synthesis
General procedure for the synthesis of aminothiazole acid from ethyl (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetate (Example 2): in a 250 ml reaction vial, 45.9 g (0.2 mol) of ethyl (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetate was suspended in 200 ml of ethanol, followed by the addition of 1 N sodium hydroxide aqueous solution. The reaction mixture was stirred at room temperature for 15 hours. Upon completion of the reaction, the pH of the reaction solution was adjusted to 7.0 with 10% aqueous hydrochloric acid, followed by distillation under reduced pressure to remove the ethanol. The aqueous phase was washed with ethyl acetate and the pH was adjusted again with 10% aqueous hydrochloric acid to 2.8. Stirring was carried out under cooling conditions in an ice bath to induce the precipitation of crystals. The crystals were separated by filtration, washed with acetone and finally recrystallized from ethanol to give 22.9 g of 2-(2-aminothiazol-4-yl)-2-(Z)-methoxyiminoacetic acid in 57.0% yield.
