Design, synthesis, SAR, and biological evaluation of highly potent benzimidazole-spaced phosphono-alpha-amino acid competitive NMDA antagonists of the AP-6 type.

A series of 2-amino-(phosphonoalkyl)-1H-benzimidazole-2-alkanoic acids was synthesized and evaluated for NMDA receptor affinity using a [3H]CPP binding assay. Functional antagonism of the NMDA receptor complex was evaluated in vitro using a stimulated [3H]TCP binding assay and in vivo by employing an NMDA-induced seizure model. Several compounds of the AP-6 type demonstrated potent and selective NMDA antagonistic activity both in vitro and in vivo.

Design and models for estimating antagonist potency (pA2, Kd and IC50) following the detection of antagonism observed in the presence of intrinsic activity.

The antagonist activity of the metabotropic glutamate receptor ligand (2S,1'S,2'S)-2-methyl-2(carboxycyclopropyl)glycine (MCCG) was examined using the [35S]GTPgammaS binding and forskolin (FSK)-stimulated adenosine 3':5'-cyclic monophosphate (cAMP) assays with recombinant Chinese hamster ovary (CHO) cells expressing the G protein-coupled human subtype 2 metabotropic glutamate (hmGlu2) receptor. Whereas MCCG proved to be a partial agonist in the GTPgammaS binding assay, it not only antagonized the agonist effect of (IS,3R)-ACPD in the cAMP assay but further produced an anomalous increase of the cAMP level relative to baseline. The anomalous MCCG response was also observed following treatment of the cells with MCCG in the absence of added agonist.

A [35S]GTPgammaS binding assessment of metabotropic glutamate receptor standards in Chinese hamster ovary cell lines expressing the human metabotropic receptor subtypes 2 and 4.

The activities of metabotropic glutamate receptor (mGluR) standards were evaluated in the [35S]GTPgammaS binding assay and in the forskolin (FSK)-enhanced cyclic AMP assay using Chinese hamster ovary (CHO) cells or homogenates which expressed the human mGluR (hmGluR) subtypes 2 and 4. Though distinct rank orders of activities were determined for the agonists between the cell lines expressing individual hmGluRs, similar rank orders of agonist activities were determined for the standards between assays. O-phospho-L-serine (L-SOP) and (S)-2-amino-2-methyl-4-phosphonobutanoic acid (MAP4) antagonized agonist EC90 responses in the cell lines expressing the hmGluR 2 and 4 subtypes, respectively.

Design and synthesis of [2-(8,9-dioxo-2,6-diazabicyclo[5.2.0]non-1(7)-en-2-yl)-ethyl]phosphonic acid (EAA-090), a potent N-methyl-D-aspartate antagonist, via the use of 3-cyclobutene-1,2-dione as an achiral alpha-amino acid bioisostere.

The diazabicyclic amino acid phosphonate 15, [2-(8,9-dioxo-2,6-diazabicyclo[5.2.0]non-1(7)-en-2-yl)ethyl]phosphonic acid, was identified as a potent NMDA antagonist.