The alkylation of 3-hydroxy-5-methoxy-1-phenylindole-2-carboxylic acid methyl ester (I) with isopropyl bromide (II) and KOH gives the corresponding 2-isopropoxy compound (III), which is hydrolyzed with KOH and HOAc, yielding the carboxylic acid (IV). The condensation of (IV) with 1H-tetrazol-5-amine (V) by means of CDI affords the expected amide (VI), which is finally treated with L-arginine to furnish the target arginine salt.