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29427-58-5

Preparation of Example 39: Synthesis of 1.3-dimethoxycarbonyl-O-methylisourea Procedure: 1. MeOH-H2SO4 solution was prepared by slowly adding sulfuric acid (112.7 g, 0.97 mol) to pre-cooled methanol (150 mL). 2. In another flask, cyanamide (50 g, 1.19 mol) was dissolved in methanol (100 mL) and cooled to about 5° C. in an ice water bath and cooled to about 5 °C. 3. The MeOH-H2SO4 solution was slowly added dropwise to the methanol solution of cyanamide while maintaining the reaction temperature at no more than 10 °C for 2 h. 4. After the dropwise addition was completed, the reaction mixture was continued to be stirred at the same temperature for 1 h. 5. At the end of the reaction, the solvent was removed by concentration in vacuum to afford O-methylisourea hydrogensulfate as a thick, syrupy product, assuming a yield of 1.5 mmol. syrupy product, assuming quantitative yield, which was used directly in the subsequent reaction.