DIEA (10.5 ml, 60 mmol) was added at 0° C. over a mixture of 1-amino-3-bromo-N-phenyl-1H-pyrrole-2-carboxamide (5.1 g, 18 mmol) and 2-(benzyloxycabonylamino)acetic acid (5.33 g, 25 mmol) in anhydrous ethyl acetate (100 ml). After 15 min T3P® solution (50% AcOEt, 15 ml) was slowly added and stirred 20 min at 0° C. and then at room temperature overnight. Further DIEA (5 ml, 30 mmol), 2-(benzyloxycabonylamino)acetic acid (2.66 g, 25 mmol) and T3P® solution (50% AcOEt, 7 ml) were added and the reaction mixture was stirred at room temperature overnight. More ethyl acetate was added and the reaction crude was washed with water and brine, dried over magnesium sulphate and the solvent was removed under vacuum. The residue was purified by flash chromatography using Isolera® Purification System (0-40%, hexane-AcOEt) to give 7.81 g (41% yield) of the final product with a purity of 45% that was used in the next step without further purification.
