The alkylation of 1H-indole-2-carboxylic acid methyl ester (I) with 2-phenylethyl bromide (II) by means of NaH in DMF gives 1-(2-phenylethyl)-1H-indole-2-carboxylic acid methyl ester (II), with is hydrolyzed with NaOH in methanol/water yielding the corresponding free acid (IV). Finally, this compound is condensed with guanidine by means of CDI and TEA in THF/DMF.