7-Arylpiperazinylalkyl and 7-tetrahydroisoquinolinylalkyl derivatives of 8-alkoxy-purine-2,6-dione and some of their purine-2,6,8-trione analogs as 5-HT1A, 5-HT2A, and 5-HT7 serotonin receptor ligands Original Research Article

On the basis of our earlier studies with the serotonin receptor ligands in the group of 1,3-dimethyl-3,7-dihydropurine-2,6-dione derivatives, a series of new arylpiperazinylalkyl and tetrahydroisoquinolinylalkyl analogs of 8-alkoxy-1,3-dimethyl-3,7-dihydropurine-2,6-dione (10–25) and 1,3-dimethyl-7,9-dihydro-3H-purine-2,6,8-trione (26–30) were synthesized and their 5-HT1A, 5-HT2A, and 5-HT7 receptor affinities were determined. The new compounds 17, 18, 20, and 21 were found to be highly active 5-HT1A receptor ligands (Ki = 11–19 nM) with diversified affinity for 5-HT2A receptors (Ki = 15–253 nM). Compounds 12, 13, 15, and 19 were moderately potent 5-HT2A ligands (Ki = 23–57 nM), whereas 17, 18, 24, and 25 showed distinct affinity for 5-HT7 receptors (Ki = 51–83 nM). Purine-2,6,8-triones showed weak affinities for 5-HT1A and 5-HT7 receptors; among them, 27 and 29 were classified as 5-HT2A receptor ligands.