Synthesis of New 5,6,7,8-Tetrahydropyrido[1,2-c]pyrimidine Derivatives with Rigidized Tryptamine Moiety As Potential SSRI and 5-HT1A Receptor Ligands.

Extended studies in the 4-aryl-pyrido[1,2-c]pyrimidine group resulted in 27 new compounds (10.1-10.27), 5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine derivatives. In vitro tests (RBA) were carried out for 10.1-10.27 compounds in order to determine their affinity to 5-HT1A receptor and SERT protein. 10.1-10.3, 10.6, 10.7, 10.16 and 10.27 compounds had high binding ability to both molecular targets (5-HT1A Ki = 8-87 nM; SERT Ki = 8-52 nM). For these compounds (10.1-10.3, 10.6, 10.7, 10.16, 10.27) further in vitro, in vivo and metabolic stability tests were performed. In vitro studies in the extended receptor profile (D2, 5-HT2A, 5-HT6 and 5-HT7) showed their selectivity towards 5-HT1A receptor and SERT protein. In vivo tests revealed that compounds 10.7 and 10.16 had the properties of presynaptic antagonists of the 5-HT1A receptor. The redesign of the 2H-pyrido[1,2-c]pyrimidine residue present in the terminal part towards 5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine resulted in the improved metabolic stability and enhanced affinity to both molecular targets (5-HT1A-R and SERT) compared to the precursors.