Methyl N-(tert-butoxycarbonyl)-L-threoninate

2592-18-9

77-78-1

60538-19-4

The general procedure for the synthesis of Boc-D-alanine methyl ester from (2S,3R)-2-((tert-butoxycarbonyl)amino)-3-hydroxybutanoic acid and dimethyl sulfate was as follows: 1) Synthesis of N-Boc-L-threonine methyl ester: Potassium carbonate (34.7 g, 250 mmol) and dimethyl sulfate (29.3 g, 232 mmol) were sequentially added to a solution of N-Boc-L-threonine (50.0 g, 213 mmol) in acetone (250 mL). The reaction mixture was heated to reflux for 1 h and subsequently cooled to room temperature in air. Insoluble solids were removed by filtration and the filtrate was concentrated under reduced pressure to remove the solvent to afford N-tert-butoxycarbonyl-L-threonine methyl ester as a colorless oil (54.6 g, 100% yield). The product was characterized by 1H-NMR (300 MHz, DMSO-d6): δ 1.26 (3H, d, J = 6.42 Hz), 1.46 (9H, s), 2.02 (1H, d, J = 5.14 Hz), 3.78 (3H, s), 4.28 (1H, m), 5.29 (1H, m). Mass spectra (FAB) showed molecular ion peak m/z: 234 ([M + H]+).