Structure melatonin (top) vs.<unk>  (bottom). The chemical structure of<unk>  is very similar to that of melatonin. Where melatonin has an indole ring system,<unk>  has a naphthalene bioisostere instead. Synthesis<unk> -synthesis: and structure-activity studies:
Agomelatine
Tropisetron
Granisetron
Alosetron
Avacopan
Cabergoline
Loteprednol
Cilansetron