A synthesis and pharmacological evaluation of new melatonin receptor ligands obtained by 2-substitution of melatonin with (indol-1-yl)methyl, (isoindolin-2-yl)methyl, and (tetrahydroisoquinolin-2-yl)methyl groups is reported. The isoindoline analogue a displays high MT2 binding affinity (Ki ¼ 2 nM) and high selectivity towards the MT2 subtype (Ki MT1/Ki MT2 ¼ 124) behaving as an MT2-antagonist.