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Four related series of substituted quinoxalinediones containing angular fused-piperidine rings have been synthesized as alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists with potential as neuroprotective agents, primarily for acute therapy immediately following a stroke. The compounds were tested for their affinity to the AMPA, kainate, and strychnine-insensitive glycine receptor sites. In AMPA binding, the most potent compound was 27a (PNQX, IC50 = 63 nM), with affinity comparable to the literature standard 1 (NBQX, IC50 = 52 nM). Other 6-nitro analogs from the 9-aza series had comparable affinity at the AMPA receptor, as did 6-nitro-8-aza derivatives such as 13a (iPNQX, IC50 = 290 nM). The receptor binding profile of 27a differed from that of 1 in that 27a possessed significant affinity at the glycine site of the N-methyl-D-aspartate (NMDA) receptor, whereas 1 was essentially inactive. Three compounds, 26c, 26d, and 26e, demonstrated moderate selectivity for kainate relative to AMPA receptors. Selected analogs reported herein as well as in the literature were superimposed to generate an AMPA pharmacophore model, and 6-substituted compounds from the PNQX and iPNQX series were combined and analyzed via quantitative structure-activity relationship techniques. Compounds with high affinity at non-NMDA receptors were further characterized in functional assays in neuronal cell culture and in a cortical wedge preparation. Both 1 and 27a showed comparable effectiveness in an AMPA- and kainate-induced excitoxicity assay. Both inhibited AMPA-induced depolarizations in the cortical wedge. However, 27a also inhibited spontaneous epileptiform discharges in the cortical wedge (reversed by glycine), while 1 was ineffective. The combination of AMPA and NMDA antagonist activity may contribute to the 30-fold difference in potency between 27a and 1 in the maximal electroshock convulsant assay in mice. The significant in vivo potency of 27a suggests that it has potential clinical utility.

Herein, we report the discovery of novel, proline-based factor Xa inhibitors containing a neutral P1 chlorophenyl pharmacophore. Through the additional incorporation of 1-(4-amino-3-fluoro-phenyl)-1H-pyridin-2-one 22, as a P4 pharmacophore, we discovered compound 7 (PD 0348292). This compound is a selective, orally bioavailable, efficacious FXa inhibitor that is currently in phase II clinical trials for the treatment and prevention of thrombotic disorders.

The preparation and binding affinity of a series of tetrahydroisoquinoline carboxylic acids at the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor is described, together with a molecular modeling analysis of NMDA agonists and antagonists. Using published NMDA ligands, the active analogue mapping approach was employed in the generation of an agonist pharmacophore model. Although known competitive antagonists such as CPP (1) could be superimposed onto the agonist model, to overcome the assumption that they bind to the same receptor site, an independent modeling approach was used to derive a separate pharmacophore model. Development of a competitive antagonist model involved a stepwise approach that included the definition of a preferred geometry for PO3H2-receptor interactions, multiple conformational searches, and the determination of volume and electronic tolerances. This model, which is described in detail, is consistent with observed affinities of potent NMDA antagonists and has provided an explanation for the observed periodicity in affinities for the known antagonists AP5, AP6, and AP7. The features of the agonist and antagonist models are compared, and hypotheses advanced about the nature of the receptor interactions for these two classes of compounds. The pharmacophore models reported herein are consistent with a single recognition site at the NMDA receptor that can accommodate both agonist and antagonist ligands. To assist in first defining and later exploring the predictive power of the competitive antagonist model, a series of conformationally constrained NMDA antagonist (phosphonoalkyl)tetrahydroisoquinoline-1- and 3-carboxylates was prepared. From this work, 1,2,3,4-tetrahydro-5-(2-phosphonoethyl)-3- isoquinolinecarboxylic acid (89) was identified as the most active lead structure, with an IC50 of 270 nM in [3H]CPP binding. The synthesis and structure-activity relationships of these novel antagonists are described.