A solution of 5-(4-methylphenyl)isoxazole-4-carboxylic acid (10 mg, 0.05 mmol), TBTU (19 mg, 0.06 mmol, 1,2 equ.) and N-ethyl-N-isopropylpropan-2-amine (26 μL, 0.15 mmol, 3 equ) in DMF (0.3 mL) was added to 3-phenylpyrrolidine hydrochloride (10 mg, 0.05 mmol) and the reaction mixture was left at rt for 2 h. The solvent was evaporated and the crude product was purified by RP-HPLC. After evaporation of the solvents the product was dried in vacuum to yield the title compound (7 mg). MS (ESI, pos. ion) m/z calcd for C21H20N2O3: 348.1474, found 348.1470.
