In a round bottom flask was added crude (R)-2-(5-Bromo-thiophene-2-sulfonylamino)-3-(1H-indol-3-yl)-propionic acid (3) (60 mg, 0.14 mmol), p-tolyl acetylene 4 (480 mg, 0.41 mmol), PdCl2P(PPh3)2 (10 mg, 0.015 mmol), copper(I)iodide (2 mg, 0.01 mmol) and triethylamine (0.025 g, 0.25 mmol) and then dissolved in dry DMF (2 mL) under an atmosphere of nitrogen. The reaction mixture was then heated at 50° C. under a nitrogen atmosphere for 2 hours. The reaction mixture was then cooled to room temperature and diluted with ethyl acetate and washed with a solution composed of NaCl/NaHCO3/(NH4)2CO3/water (1:1:1:1) (×3), water, and then dried over sodium sulfate (Na2SO4). The crude product was purified using a SAX column to provide to give the desired (R)-3-(1H-Indol-3-yl)-2-(5-p-tolylethynyl-thiophene-2-sulfonylamino)-propionic acid 5 (0.036 g, 55%).
