The known N-Boc-agmatine-N-G-sulfonylphenoxyacetic acid (I) was coupled to 4-methylbenzhydrylamine resin by using DIC and HOBt to afford resin (II). Subsequent cleavage of the Boc protecting group with trifluoroacetic acid yielded amine (III). The corresponding protected amino acids were assembled to the amine-bound resin (III) using solid-phase peptide synthesis methodology. Couplings were carried out with the symmetrical anhydride of the Boc-amino acids or with the preformed HOBt ester in the case of Boc-Asn, and each coupling was followed by Boc group cleavage with trifluoroacetic acid in CH2Cl2.

The final side chain-protected peptide resin (IV) was then simultaneously cleaved and deprotected by treatment with liquid hydrogen fluoride in the presence of anisole.

The known N-Boc-agmatine-N-G-sulfonylphenoxyacetic acid (I) was coupled to 4-methylbenzhydrylamine resin by using DIC and HOBt to afford resin (II). Subsequent cleavage of the Boc protecting group with trifluoroacetic acid yielded amine (III). The corresponding protected amino acids were assembled to the amine-bound resin (III) using solid-phase peptide synthesis methodology. Couplings were carried out with the symmetrical anhydride of the Boc-amino acids or with the preformed HOBt ester in the case of Boc-Asn, and each coupling was followed by Boc group cleavage with trifluoroacetic acid in CH2Cl2.

The final side chain-protected peptide resin (IV) was then simultaneously cleaved and deprotected by treatment with liquid hydrogen fluoride in the presence of anisole.