Cyclic Amidines as Benzamide Bioisosteres: EPC Synthesis and SAR Studies Leading to the Selective Dopamine D4 Receptor Agonist FAUC 312

Investigation of conformationally restricted benzamide bioisosteres led to the chiral phenyltetrahydropyrimidine derivative ent2a (FAUC 312) displaying strong and highly selective dopamine D4 receptor binding (Kihigh=1.5 nM). Mitogenesis experiments indicated 83% ligand efficacy when compared to the unselective agonist quinpirole. The target compounds of type 2 and 3 were synthesized in enantiopure form starting from asparagine.