To a solution of 15 mg (0.08 mmol) of 5-chloro-1H-indole-7-carboxylic acid and 24 mg of TBTU (0.08 mmol) in 1.5 ml DMF, were added 0.066 ml (0.38 mmol) of N,N-diisopropylethyl amine in 1 ml DMF. After stirring for 5 min at rt, 25 mg (0.08 mmol) of [rac]-(4-tert-butyl-benzyl)-[2-(4-chloro-phenyl)-2-fluoro-ethyl]-amine were added. After stirring for 17 h at rt, the reaction mixture was diluted with 40 ml water and extracted with EtOAc (2×). The combined organic phases were washed with water and brine, dried with magnesium sulfate, filtered and concentrated in vacuo. The residue was purified by column chromatography (8 g silica gel; heptane/EtOAc 4:1) to give 9 mg (21%) of a light yellow solid. MS (ISP): 497.3 (M+H)+.
