Allyl bromide → N-(t-Butoxycarbonyl)-D-tryptophan Allyl Ester

N-(t-Butoxycarbonyl)-D-tryptophan (3 g; 9.868 mmol) was dissolved in acetone and an aqueous solution of potassium carbonate (2.84 g; 20.58 mmol) added followed by allyl bromide (1.55 g; 12.81 mmol). The reaction mixture was stirred for 18 h and then the acetone was substantially removed by evaporation under reduced pressure. The oily water layer that remained was acidified to approximately pH=5 with 1N-hydrochloric acid and then extracted with methylene chloride. The methylene chloride layer was dried over anhydrous magnesium sulfate powder, filtered and evaporated under reduced pressure to give a foamy solid. The foam was further purified by column chromatography using silica gel and ethyl acetate and hexanes 2:1 v/v as eluant. In this manner, a 1.92 g yield (56%) of the desired product was obtained as an off white solid. FAB-MS:- calculated for C19H24N2O4 344; found 344 (M).