24424-99-5

78-96-6

95656-86-3

Step 1: 1-Amino-2-propanol (compound 42.1; 3.53 g, 47.0 mmol) and triethylamine (25 mL) were dissolved in methanol (35 mL) under nitrogen protection. Subsequently, a solution of di-tert-butyl dicarbonate (10.3 g, 47.0 mmol) in methanol (15 mL) was added slowly and dropwise. The reaction mixture was stirred overnight at room temperature. Upon completion of the reaction, the mixture was concentrated and the residue was dried under high vacuum to give 8.23 g (quantitative yield) of clear oily product. This oily product was dissolved in tetrahydrofuran (100 mL) and triethylamine (13.1 mL, 94.0 mmol) was added. Methanesulfonyl chloride (3.82 mL, 49.3 mmol) was added dropwise to this solution at 0 °C. After 1 h of reaction, the mixture was diluted with ethyl acetate and washed sequentially with 1 M aqueous hydrochloric acid, aqueous sodium bicarbonate and brine. The organic phase was dried with anhydrous sodium sulfate and concentrated to give 10.5 g (88% yield) of a clear oily product (compound 42.2), which solidified on standing. Electrospray mass spectrometry (ES(+)MS) showed m/e = 254 ([M+H]+).