Design and Synthesis of New N-OMe Fluoro-Indole Melatoninergics

The synthesis of a series of new N-OMe fluoro-indoles with melatoninergic activity in the Xenopus melanophore assay is described. All of the 4-F substituted compounds, 22a-e and 25a,b, were antagonists on the clonal Xenopus melanophore line. Conversely, the 5-F substituted analogs (15a-e) did not share the same pharmacological profile, as two of them, compounds 15d (R=c-C3H5) and 15e (R=c-C4H7), exhibited a weak agonistic and partial agonistic activity, respectively, whilst the other three (15a-c) were all agonists. It seems that in this case the nature of the response (agonist or antagonist activity) is solely dependent on the shape of the R group.