173998-77-1

24424-99-5

14527-26-5

173998-77-1

GENERAL STEPS: To a rapidly stirred suspension of S-methylisothiourea sulfate (60.8 g, 0.437 mol) in dichloromethane (600 mL) was slowly added 2 N sodium hydroxide solution (300 mL, 0.6 mol). The reaction mixture was cooled to 0 °C in an ice bath and a dichloromethane solution of di-tert-butyl dicarbonate (43.2 g, 0.198 mol) was slowly added dropwise over a period of 6 hours. After the dropwise addition, the reaction mixture was continued to be stirred at 0 °C for 20 min. Subsequently, the reaction mixture was diluted with dichloromethane (1 L) and the organic and aqueous phases were separated. The organic phase was washed sequentially with water (2 x 500 mL) and dried over anhydrous sodium sulfate. The desiccant was removed by filtration and the filtrate was concentrated under reduced pressure to afford the target product 1-N-Boc-2-methylisothiourea as a white solid (35.5 g, 0.187 mol, 94% yield as di-tert-butyl dicarbonate).