A mixture of 0.043 g of 2-methyl-4-(4-trifluoromethyl-benzyl)-4H-thieno[3,2-b]pyrrole-3-carboxylic acid, 0.060 g of (S)-4-(1-amino-ethyl)-benzoic acid methyl ester, 0.040 g of HOBT-hydrate, 0.054 g of ethyl-dimethylaminopropyl-carbodiimide hydrochloride (EDCI) and 0.060 ml of N-methylmorpholine in 2 ml of DMF was stirred at room temperature for 18 h. The reaction was then quenched with 1 ml of water and 2 ml of saturated NaHCO3 solution. The resulting mixture extracted with 15 ml of EtOAc. The organic layer was dried over Na2SO4, filtered, and concentrated to give the crude methyl ester which was dissolved in 2 ml THF, 2 mL MeOH and 0.5 mL water and treated with 0.5 mL of 1M LiOH solution. After stirring for 24 h at room temperature, the reaction mixture was concentrated under reduced pressure to remove THF and MeOH. The residue was diluted with 2 mL of water and treated with 0.3 mL of AcOH with vigorous stirring. After stirring for 2 h, the solid was collected by filtration and air-dried to give 0.029 g of the title compound as a white powder.
