Trifluoroacetic acid → H-L-Ile-D-Pro-OBzl-TFA

Participants

Reaction Steps

Boc-L-Ile-D-Pro-OBzl (21.5 g, 51.4 mmol) was dissolved in TFA (50 ml) and left with standing on ice for one hour. On completion of the reaction, TFA was removed by evaporation, and the residue was vacuum-dried to obtain H-L-Ile-D-Pro-OBzl-TFA. The compound was dissolved in DMF (100 ml), and Boc-D-Tyr(Me)-OH (16.7 g, 56.5 mmol) was then added. HBTU (29.4 g, 77 mmol), HOBt.H2O (7.87 g, 51 mmol), and triethylamine (25.2 ml, 180 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 compound (22.0 g, 37 mmol, 72% yield). TLC: Rf=(CHCl3/MeOH=9/1).

Provenance & Evidence