Novel 1-(azacyclyl)-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines as 5-HT6 agonists and antagonists Original Research Article

1-Aminoethyl-3-arylsulfonyl-1H-indoles 1 are 5-HT6 receptor ligands with modest activity in a 5-HT6 cyclase assay. Introduction of an additional nitrogen in the indole ring provides 1-aminoethyl-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines 2 with both enhanced 5-HT6 affinity and cyclase activity, many acting as 5-HT6 agonists. We constrained the basic side chain as part of a ring to make 1-(azacyclyl)-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines incorporating a pyrrolidinyl 3 or piperidinyl 4 ring system. Preparation of compounds 3 and 4 required synthesis of the key intermediates, 1-(pyrrolidin-3-yl)-1H-pyrrolo[2,3-b]pyridines 7 and 1-(piperidin-3-yl)-1H-pyrrolo[2,3-b]pyridines 8, respectively. Intermediates 7 were prepared through alkylation of 7-azaindole while the intermediates 8 required an alternate synthesis. The compounds of both series 3 and 4 were shown to have high binding affinities for the 5-HT6 receptor. The in vitro functional activity at the 5-HT6 receptor varied depending on various functionalities including the selection of the arylsulfonyl, the substitution on the arylsulfonyl group, the ring size, and the substitution on the basic amine moiety producing either 5-HT6 receptor agonists or antagonists.