The discovery of the selective AMPA antagonist character of 2,3-benzodiazepine derivative GYKI 52466 (5) in the late eighties and the recognition of the non-competitive nature of its mode of action some years later set off the world-wide search for novel class of drugs. Notably the quest to develop new antiepileptic and neuroprotective medicines, which allosterically inhibit the AMPA sensitive glutamate operated channels. This review summarises our present knowledge about the allosteric site, dubbed "GYKI site" where the 2,3-benzodiazepines are supposed to bind to. The structure-activity relationships among AMPA antagonist 2,3-benzodiazepines and their structural analogues with similar biological profile are reviewed in a possibly comprehensive fashion. The chemical synthesis of 2,3-benzodiazepines is shortly described. The in vitro and in vivo experimental methods used for pharmacological characterisation of the biologically active compounds are briefly explained. Finally the therapeutic potential of 2,3-benzodiazepines i.e. the main fields of their clinical utility are outlined with special regard to talampanel (20) in the light of the ongoing clinical trials with this new drug candidate.

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Seven (S)-3-methylisochromans with different substitution patterns on their aromatic rings, and hence with different directions of their sum electric transition moments, were synthesized by ring-closure of optically active (S)-1-arylpropan-2-ol derivatives. The (S)-1-rylpropan-2-ols were obtained by kinetic resolution and their absolute configurations were determined with the aid of a zinc porphyrin tweezer and by Mosher’s method. A systematic CD study of substituted isochroman derivatives revealed that, unlike in the cases of chiral tetralin and 2,3-dihydrobenzo[b]furan chromophores, the presence of achiral substituents of large spectroscopic moment (e.g., OMe) on the aromatic ring does not change the helicity rule of the “unsubstituted” isochroman chromophore: (P)/(M) helicity of the isochroman heteroring resulted in positive/negative 1Lb band Cotton effects (CE) regardless of the nature(s) and position(s) of the substituent(s). (S)-3-Methylisochromans were oxidized at C-1, allowing access to the corresponding dihydroisocoumarins, in which positive CE of the nπ* transitions were correlated with (P) helicity and (S) absolute configuration. On DDQ-assisted oxidation, two trans-1-methoxy-3-methylisochroman derivatives were prepared and used to study the effect of the axial benzylic C-1 methoxy group on the conformation of the heteroring and the 1Lb band CE

2,3-Benzodiazepine compounds are synthesized as drug candidates for treatment of various neurological disorders involving excessive activity of AMPA receptors. Here we report that pairing a thiadiazole moiety with a 2,3-benzodiazepine scaffold via the N-3 position yields an inhibitor type with >28-fold better potency and selectivity on AMPA receptors than the 2,3-benzodiazepine scaffold alone. Using wholecell recording, we characterized two thiadiazolyl compounds, that is, one contains a 1,3,4-thiadiazole moiety and the other contains a 1,2,4-thiadiazole-3-one moiety. These compounds exhibit potent, equal inhibition of both the closed-channel and the open-channel conformations of all four homomeric AMPA receptor channels and two GluA2R-containing complex AMPA receptor channels. Furthermore, these compounds bind to the same receptor site as GYKI 52466 does, a site we previously termed as the "M" site. A thiadiazole moiety is thought to occupy more fully the side pocket of the receptor site or the "M" site, thereby generating a stronger, multivalent interaction between the inhibitor and the receptor binding site. We suggest that, as a heterocycle, a thiadiazole can be further modified chemically to produce a new class of even more potent, noncompetitive inhibitors of AMPA receptors.

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