Indoline-2-carboxylic acid (I) is converted into the N-Boc derivative (II) by treatment with Boc2O. Subsequent coupling of (II) with methyl indoline-2-carboxylate (III) by using 2-chloro-1-methylpyridinium iodide (CMPI) provides amide (IV). Hydrolysis of the methyl ester function of (IV) employing LiOH leads to carboxylic acid (V). This is then coupled to N-epsilon-(benzyloxycarbonyl)-lysine methyl ester (VI) in the presence of CMPI to furnish the title compound.