L-Aspartic Acid → N-(Benzyloxycarbonyl)aspartic acid

Participants

Reaction Steps

Aspartic acid (100 g, 0.75 mol) was suspended in 400 ml methylene chloride and stirred mechanically. Trimethylsilyl chloride (244 g, 2.25 mol) was added. The mixture was refluxed for 1.5 hours and then cooled in an ice bath. Triethylamine (303 g, 3.0 mol) was slowly added with stirring and cooling. Carbobenzoxy chloride (128 g, 0.75 mol) was slowly added with cooling. The mixture was stirred for 2 hours at 0° C. and then warmed to RT for 2 hours. The reaction mixture was poured into a stirred mixture of 500 ml 2.5% NaHCO3 and 500 ml Et2O. The layers were separated and the aqueous phase was extracted with 3×300 ml Et20. The aqueous layer was acidified to pH 2 with conc. HCl and extracted with 3×200 ml EtOAc. The combined organic layers were dried over MgSO4, filtered and concentrated to a white solid. Recrystallization from 290 ml H2O yielded 145 g (72.3%) Z-aspartic acid.

Provenance & Evidence