4-substituted-3-phenylquinolin-2(1H)-ones: acidic and nonacidic glycine site N-methyl-D-aspartate antagonists with in vivo activity.

4-Substituted-3-phenylquinolin-2(1H)-ones have been synthesized and evaluated in vitro for antagonist activity at the glycine site on the NMDA (N-methyl-d-aspartate) receptor and in vivo for anticonvulsant activity in the DBA/2 strain of mouse in an audiogenic seizure model. 4-Amino-3-phenylquinolin-2(1H)-one (3) is 40-fold lower in binding affinity but only 4-fold weaker as an anticonvulsant than the acidic 4-hydroxy compound 1. Methylsulfonylation at the 4-position of 3 gives an acidic compound (6, pKa = 6.0) where affinity is fully restored but in vivo potency is significantly reduced (Table 1). Methylation at the 4-position of 1 to give 18 results in the abolition of measurable affinity, but the attachment of neutral hydrogen bond-accepting groups to the methyl group of 18 produces compounds with comparable in vitro and in vivo activity to 1 (e.g., 23 and 28, Table 2). Replacement of the 4-hydroxy group of 1 with an ethyl group abolishes activity (42), but again, incorporation of neutral hydrogen bond...