Novel 1,2,3,4-tetrahydroisoquinolines with high affinity and selectivity for the dopamine D3 receptor

Using clearance and brain penetration studies as a screen, tetrahydroisoquinoline 3 was identified as a lead having low clearance in rats (CLb 20 ml/min/kg). Introduction of a 7-CF3SO2O- substituent into the tetrahydroisoquinoline, followed by replacement of the biphenylamido group of 3 by a 3-indolylpropenamido group gave 31, having high D3 receptor affinity (pKi 8.4) and 150 fold selectivity over the D2 receptor.