N-t-Butoxycarbonyl-L-alanine (377 mg, 2.0 mmol), HOBT (283 mg, 2.1 mmol) and EDC hydrochloride (420 mg, 2.2 mmol) were dissolved in 5 mL of DMF. Benzylamine (230 μL, 2.1 mmol) was added followed by triethylamine (280 μL, 1.9 mmol). The mixture was stirred overnight and the solvent was evaporated. The residue was partitioned between ethyl acetate and 10% citric acid and the organic phase was washed sequentially with 10% sodium bicarbonate and brine. The solution was dried and evaporated to yield 498 mg of a waxy solid.
