0.20 g (0.84 mmol) of 2-pyridin-4-yl-1H-indole-5-carboxylic acid was admixed with 0.21 g (1.07 mmol) of 2-amino-3-phenylsulfanylpropionic acid in 40 ml of DMF and, at 0° C., 0.66 g (1.27 mmol) of benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate and 0.37 ml (2.12 mmol) of N-ethyl-N,N-diisopropylamine were added, and the solution was stirred at 20° C. for 2 h. The solution was concentrated under reduced pressure and purified by medium pressure column chromatography (CH2Cl2/CH3OH:9:1). This gave 0.19 g (54%) of N-(1-carbamoyl-2-phenylsulfanylethyl)-2-pyridin-4yl-1H-indole-5-carboxamide.
