p-Toluenesulfonic acid → [(1R,2S)-1-carboxy-2-hydroxy-propyl]-methyl-ammonium toluene-4-sulfonate

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Reaction Conditions

Reaction Steps

In a heart-shaped flask, (2R,3S)-2-[tert-butoxycarbonyl-(methyl)-amino]-3-hydroxy-butanoic acid (0.086 g, 0.37 mmol) was mixed with p-TsOH (0.073, 0.39 mmol) and the solid mixture was cooled to 0° C. Subsequently TFA (2.0 mL) was added over 10 min and the reaction mixture was left to react for 15 min at 0° C. The solution was rotary evaporated maintaining the bath below 30° C. and the obtained oil was left under vacuum for 1 h. The oil was then dissolved in dry Et2O to form a white precipitate. The solution was decanted and the solid washed several times with the same solvent to give a pure product (0.11 g, quant.), as a white sticky solid. 1H NMR (DMSO-d6) δ 1.25 (d, J=6.5 Hz, 3H), 2.29 (s, 3H), 2.60 (s, 3H), 3.73-3.82 (m, 1H), 4.02-4.11 (m, 1H), 7.11 (d, J=8.1 Hz, 2H), 7.48 (d, J=8.1 Hz, 2H).

Provenance & Evidence