Synthesis and dopamine receptor binding studies of homochiral 8-aminopyrido[1,2-a]indoles

Starting from L-aspartic acid the preparation of 8-aminopyrido[1,2-a]indole derivatives as benzo-fused analogs of the dopamine autoreceptor agonist 1 is reported. The key step of the synthesis is the Tf2O induced cyclization of the 1,2-amino alcohol 6. Receptor binding studies indicated selective affinity for the D-2 autoreceptor. Among the tested compounds, the dipropylamino derivative 2 showed the highest affinity for the D-2 receptor labelled with the selective autoreceptor agonist pramipexole (IC50 value: 450 nM). Thus, 2 is 15 times less potent than the aminoindolizine 1.