Coupling of N-Boc-D-pyridylalanine (I) to glycine methyl ester (II) produced the protected dipeptide (III). Subsequent catalytic hydrogenation of the pyridine ring of (III) over PtO2 gave piperidine (IV), which was then treated with the guanylating reagent (V) to afford the guanidine derivative (VI). Acid cleavage of the Boc protecting group of (VI) provided amine (VII). This was condensed with benzylsulfonyl chloride to give sulfonamide (VIII). After basic hydrolysis of the methyl ester of (VIII), the resultant carboxylic acid (IX) was coupled to nitroargininal ethyl aminal (X), yielding amide (XI).

Hydrogenolysis of the carbobenzoxy and nitro protecting groups of (XI) furnished (XII). Finally, mild acid hydrolysis of the ethyl aminal group of (XII) gave the title compound, which was isolated as the trifluoroacetate salt.