Enaminone Amides as Novel Orally Active GABA sub(A) Receptor Modulators

A series of enaminone esters and amides have been developed as potent allosteric modulators of gamma -aminobutyric acid sub(A) (GABA sub(A)) receptors. The compounds bind to a novel modulatory site that is independent of the benzodiazepine (BZ), isosteric GABA, and neuroactive steroid binding sites. Structure-activity relationship (SAR) studies resulted in the synthesis of the c-Bu amide 16h with an in vitro potency of 7 nM based on inhibition of [ super(35)S]TBPS binding. The activity of the enaminones as positive allosteric modulators was confirmed with electrophysiological measurements in oocytes expressing alpha sub(1) beta sub(2) gamma sub(2L) GABA sub(A) receptors. The i-Pr, s-Bu, c-Pr, and c-Bu amides (16e-h) were orally active in mice with profound central nervous system depressant effects. The i-Pr amide 16e was an orally active anxiolytic in the mouse light-dark paradigm.