Nalpha-(Benzyloxycarbonyl)-1,4-diaminobutyric acid (I) was protected as the Nomega-Boc derivative (II) and then coupled to glycine ethyl ester (III) by means of EDC and HOBt to produce dipeptide (IV). Hydrogenolysis of the benzyloxycarbonyl group of (IV) to give (V), followed by condensation with alpha-toluenesulfonyl chloride (VI) gave sulfonamide (VII). Side-chain deprotection of (VII) with HCl liberated amine (VIII), which was acylated with 2-pyrazinecarboxylic acid (IX) to afford amide (X). Saponification of the ethyl ester of (X) with LiOH gave carboxylic acid (XI).

The carboxylic acid (XI) was coupled with Ngamma-Pmc-argininol (XII) giving (XIII). Deprotection of the Pmc group of (XIII) with trifluoroacetic acid provided the free guanidine (XIV). Finally, Swern oxidation of the primary alcohol of (XIV) with concomitant cyclization of the resulting aldehyde furnished the title compound.