The benzoylation of tyrosine (I) with benzoyl chloride (II) in aqueous NaOH gives O,N-(di-benzoyl)-D,L-tyrosine (III), which by reaction with di-n-propylamine (A) by means of ethyl chlorocarbonate and triethylamine in acetone is converted into O,N-(di-benzoyl)-D,L-tyrosyl-di-n-propylamide (IV). Selective hydrolysis of (IV) with NaOH in methanol - water affords N-benzoyl-D,L-tyrosyl-di-n-propylamide (V), which is finally condensed with 2-(diethylamino)ethyl chloride (VI) by means of sodium methoxide in refluxing toluene.