Trifluoroacetic acid → H-L-Ile-D,L-Pip-OBzl TFA

Participants

Reaction Steps

Boc-L-Ile-D,L-Pip-OBzl (432 mg, 1 mmol) was dissolved in TFA (3 ml) and allowed to stand for 30 minutes under ice cooling. The reaction solution was distilled and dried under reduced pressure to yield H-L-Ile-D,L-Pip-OBzl TFA (638 mg; yield 144%), which was then dissolved in DMF (5 ml). The solution was mixed with Boc-D-Cha-OH (326 mg, 1.2 mmol) and subsequently mixed with HOBt H2O (230 mg, 1.5 mmol, 1.5 equivalents), Et3N (0.52 ml, 3.7 mmol, 3.7 equivalents) and BOP (663 mg, 1.5 mmol, 1.5 equivalents) under ice cooling, followed by stirring at room temperature for 15 hours. The reaction mixture was concentrated, extracted with ethyl acetate (100 ml), and washed twice with 10% citric acid, 4% NaHCO3 and brine, respectively. After drying over magnesium sulfate, ethyl acetate was distilled off. The residue was vacuum dried and purified by flash chromatography (2.4×14 cm) with CHCl3/MeOH (99:1) to yield Boc-D-Cha-L-Ile-D,L-Pip-OBzl (565 mg, 0.96 mmol; yield 96%) as a foam.

Provenance & Evidence