Synthesis and Applications of Polyamine Amino Acid Residues: Improving the Bioactivity of an Analgesic Neuropeptide, Neurotensin

Conjugated polyamines are potential carriers for biotherapeutics targeting the central nervous system. We describe an efficient synthesis of a polyamine-based amino acid, lysine-trimethylene(diNo-syl)-spermine(triBoc) with Dde or Fmoc orthogonal protecting groups. This nonnatural amino acid was incorporated into a neurotensin analogue using standard Fmoc-based protocols. The analogue maintained high affinity and agonist potency for neurotensin receptors and exhibited dramatically improved analgesia in mice. Our work provides a basis for use of polyamine amino acids in polypeptides.