[Synthesis and biological activity of cyclic and linear analogs of C-terminal fragments of neurotensin].

Using solid-phase approach, new cyclic and linear analogues of C-terminal neurotensin (NT) fragments were synthesized and their vasodepressor and miotropic activities were assayed. The cyclic structures were fixed by a peptide bond linking the lysine epsilon-amino group with the C-terminal carboxyl. Cyclization was performed by using pentafluorophenyl esters or diphenylphosphorylazide.