Hydrochloric Acid → Fmoc-L-aspartic acid

Participants

Reaction Steps

Forty-five g (0.134 M, 0.96 eq) of Fmoc-Osu was added to 20 g (0.15 M, 1 eq) of aspartic acid and 20 g of Na2CO3 dissolved in 400 mL of water and 200 mL of dioxane. The mixture was stirred for 2 hrs while the pH was maintained at about 9 by the addition of small amounts of Na2CO3. Then the cloudy white mixture was poured into 500 mL of ice water containing 40 mL of conc HCl. The white solid was extracted with 500 mL EtOAc and this was mixed with 500 mL of hexane. The mixture was chilled overnight and stirred the next day to give 38 g of Fmoc-aspartic acid as crystals (71% yield) upon filtration and air drying. 10 g (0.28 M) of this product was dissolved in 200 mL of methanol and 20 mL of conc H2SO4 was added. The solution was allowed to stand overnight. The mixture was poured into 1 L of water and filtered. The resulting white solid was dried and redissolved in EtOAc. Slow addition of hexane and chilling gave 9 g (83% yield) of product as white needles, mp 78-80°. [a]d =-13.9°.

Provenance & Evidence