Rigid linkers of variable length were synthesized and used to connect two NDP-α-MSH ligands. The linkers were incorporated by solid-phase synthesis. Biological evaluations indicate that there is virtually no effect of these linkers on ligand binding to the human melanocortin 4 receptor.
[Fletcher, David I.; Ganellin, C. Robin; Piergentili, Alessandro; Dunn, Philip M.; Jenkinson, Donald H. Bioorganic and Medicinal Chemistry, 2007 , vol. 15, # 16 p. 5457 - 5479]