Trifluoroacetic acid → 2-((1R)-1-((2R)-2-amino-3-(2-naphthyl)propionylamino)-2-(2-naphthyl)ethyl)-5-phenyl-1,3-thiazole-4-carboxylic acid amide

((1R)-1-((1R)-1-(4-Carbamoyl-5-phenyl-1,3-thiazol-2-yl)-2-(2-naphthyl)ethylcarbamoyl)-2-(2-naphthyl)ethyl)carbamic acid tert-butylester (0.22 g; 0.328 mmol) was dissolved in methylene chloride (2.5 ml) and trifluoroacetic acid (2.5 ml) was added. The reaction mixture was stirred 1 h at room temperature and the solvent was removed in vacuo. The residue was dissolved in methylene chloride and evaporated (2×5 ml). The residue was dissolved in methylene chloride (10 ml) and washed with sodium hydrogencarbonate (satd; 10 ml), water (10 ml) and dried (magnesium sulfate). The solvent was removed in vacuo to afford 0.155 g of 2-((1R)-1-((2R)-2-amino-3-(2-naphthyl)propionylamino)-2-(2-naphthyl)ethyl)-5-phenyl-1,3-thiazole-4-carboxylic acid amide.