3-THIENYLAMINOBUTYRIC AND 3-FURYLAMINOBUTYRIC ACIDS - SYNTHESIS AND BINDING GABA-B RECEPTOR STUDIES

Baclofen (beta-(p-chlorophenyl)-GABA) is a selective agonist for the bicuculline-insensitive GABA(B) receptor. The search for new compounds that bind to the GABA(B) receptor is very important to clarify structural requirements. We report herein the synthesis and the binding studies of variously substituted 3-thienyl- and 3-furylaminobutyric acids. 4-Amino-3-(5-methyl-2-thienyl)butyric acid (5d) and 4-amino-3-(5-chloro-2-thienyl)butyric acid (5h) are potent and specific ligands for GABA(B) receptor. The IC50 values for the displacement of (R)-(-)-[H-3]baclofen are 1.34 and 0.61-mu-M for 5d and 5h, respectively, as compared to 0.33-mu-M for baclofen.