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

Participants

Reaction Steps

Boc-L-Ile-DL-Pip-OBzl (3.33 g, 7.70 mmol) was dissolved in TFA (10 ml) and left with standing on ice for 30 minutes. On completion of the reaction, TFA was removed by evaporation, and the residue was vacuum-dried to obtain H-L-Ile-DL-Pip-OBzl.TFA. The compound was dissolved in DMF (16 ml), and Boc-D-Tyr(Me)-OH (3.41 g, 11.6 mmol) was then added. HBTU (4.38 g, 11.6 mmol), HOBt.H2O (1.18 g, 7.70 mmol), and triethylamine (7.01 ml, 50.1 mmol) were further added and stirred for 3 hours under ice-cooling. The reaction solution was concentrated, dissolved in ethyl acetate, and successively washed with an aqueous 10% citric acid solution, an aqueous 4% sodium bicarbonate solution, and saturated saline. The product was dried over MgSO4 and concentrated, and the resulting foam substance was purified by flash silica gel chromatography (4×30 cm, 1% methanol/chloroform) to obtain the foam title diastereomer mixture (3.46 g, 5.67 mmol, 74% yield). TLC: Rf=(CHCl3/MeOH=9/1).

Provenance & Evidence