0.63 g (2.64 mmol) of 2-pyridin-4-yl-1H-indole-5-carboxylic acid, prepared as in process variant B), was suspended in 150 ml of DMF and admixed successively with 1.01 g (3.08 mmol) of TOTU and 0.63 ml (3.71 mmol) of ethyidiisopropylamine. The mixture was stirred at RT for 20 min, and 0.73 g (3.28 mmol) of methyl (S)-2-amino-3-phenylaminoethylpropionate, prepared according to a), was added to the resulting clear solution. The mixture was stirred under reduced pressure for 15 h and the methyl ester of the title compound was then isolated by flash chromatography over silica gel (DCM:MeOH=19:1). Yield: 0.44 g, empirical formula C26H26N4O3; M.W.=442.2; MS (M+H) 443.3.
