S26131 (compound 5) is a potent and selective MT1 melatoninergic ligand, and the Ki values are 0.5 and 112 nM for MT1 and MT2, respectively. S26131 behaves as an MT1 and MT2 antagonist[1].
S26131 behaves as an antagonist on MT1 and MT2 receptors with KB values of 5.32 and 143 nM, respectively[1].
[1]. Descamps-FranÇois C, et al. Design and synthesis of naphthalenic dimers as selective MT1 melatoninergic ligands. J Med Chem. 2003 Mar 27;46(7):1127-9.