Two different strategies were used for the introduction of the olefinic double bonds. For the generation of dehydrovaline, base-promoted elimination of the nitro group in β-nitrovaline 1 was the method of choice , while dehydroisoleucine was introduced into the peptide backbone by a coppermediated Goldberg reaction of acylamide 5 with vinyl iodide 4 . The synthesis of unusual amino acids such as 4-hydroxyphenyl-β-alanine S7 and β-nitrovaline 1 as well as vinyl iodide 4 and amidinating agent 7 are described in the supporting information. Fragment B was obtained in 66% yield starting from protected D-ornithine 2. The Goldberg coupling was used in the synthesis of fragment C as key reaction which was achieved in satisfactory yield. Finally, fragment D was prepared from 1,4-diaminobutane 6 which was coupled with Fmoc-protected hydroxy-valine, and amidinated using the Allocprotected methyl carbamimidothioate 7 reagent.