The benzodiazepines

Flumazenil-Insensitive Benzodiazepine Effects in Recombinant αβ and Neuronal GABAA Receptors

Gamma-aminobutyric acid, type A (GABA_A) receptors are complex heterogeneous pentamers with various drug binding sites. Several lines of evidence suggest that benzodiazepines modulate certain GABA_A receptors in a flumazenil-insensitive manner, possibly via binding sites other than the classical ones. However, GABA_A receptor subtypes that contain non-classical benzodiazepine binding sites are not systemically studied. The present study investigated the high-concentration effects of three benzodiazepines and their sensitivity to flumazenil on different recombinant (α1β2, α2β2, α3β2, α4β2, α5β2 and α1β3) and native neuronal GABA_A receptors using the whole-cell patch-clamp electrophysiology technique. The classical benzodiazepine diazepam (200 μmol/L) and midazolam (200 μmol/L) produced flumazenil-insensitive effects on α1β2 receptor, whereas the imidazopyridine zolpidem failed to modulate the receptor. Flumazenil-insensitive effects of diazepam were also observed on the α2β2, α3β2 and α5β2, but not α4β2 receptors. Unlike β2-containing receptors, the α1β3 receptor was insensitive to diazepam. Moreover, the diazepam (200 μmol/L) effects on some cortical neurons could not be fully antagonized by flumazenil (200 μmol/L). These findings suggested that the non-classical (flumazenil-insensitive) benzodiazepine effects depended on certain receptor subtypes and benzodiazepine structures and may be important for designing of subtype- or binding site- specific drugs.

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

Two novel tetrafluorinated 1,5-benzodiazepinones were synthesized and their X-ray structures determined. 6,7,8,9-Tetrafluoro-4-methyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one crystallizes in the monoclinic P2₁/c space group and 6,7,8,9-tetrafluoro-1,4-dimethyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one in the triclinic P−1 space group. Density functional theory studies at the B3LYP/6-311++G(d,p) level were carried out on these compounds and on four non-fluorinated derivatives, allowing to calculate geometries, tautomeric energies and ring-inversion barriers, that were compared with the experimental results obtained by static and dynamic NMR in solution and in solid state.

Exploiting the acylating nature of the imide-Ugi intermediate: a straightforward synthesis of tetrahydro-1,4-benzodiazepin-2-ones

We describe a simple and novel protocol for the synthesis of tetrahydro-1,4-benzodiazepin-2-ones with three points of diversity, exploiting the acylating properties of the recently rediscovered Ugi-imide. The final compounds can be easily prepared in three synthetic steps using a multicomponent reaction, a Staudinger reduction, and an acylative protocol, with good to excellent yields for each synthetic step.

1,4-Benzodiazepin-2-ones in medicinal chemistry

1,4-Benzodiazepin-2-ones have applications in many areas of medicinal chemistry that are not restricted to 'classical' CNS treatments such as sedatives, epilepsy and muscle relaxants. We will describe selected examples of 1,4-benzodiazepin-2-ones in other areas of medicinal chemistry including uses as G-protein-coupled receptor antagonists, enzyme inhibitors and anticancer agents. Examples from our group will mainly show the use of palladacycle complexes of 1,4-benzodiazepin-2-ones as anticancer agents.

Novel, Achiral 1,3,4-Benzotriazepine Analogues of 1,4-Benzodiazepine-Based CCK2 Antagonists That Display High Selectivity over CCK1 Receptors

A series of 1,3,4-benzotriazepine-based CCK(2) antagonists have been devised by consideration of the structural features that govern CCK receptor affinity and the receptor subtype selectivity of 1,4-benzodiazepine-based CCK(2) antagonists. In contrast to the latter compounds, these novel 1,3,4-benzotriazepines are achiral, yet they display similar affinity for CCK(2) receptors to the earlier molecules and are highly selective over CCK(1) receptors.

Characterization of benzodiazepinooxazoles: crystal and molecular structure of trans and cis isomers of oxazolam

The stereochemistry of the trans and cis isomers of 2(S)- and 2(R)-oxazolam is described. A total of four molecular structures of the 11b(R) and 11b(S) diastereomers of 2(S)- and 2(R)-oxazolam have been revealed by X-ray diffraction techniques. 2(S)-Oxazolam crystallizes in space group P2(1)/c, with cell dimensions a = 16.180(2) A, b = 8.791(2) A, c = 13.574(2) A, and beta = 102.07(1) degrees. The molecule in an asymmetric unit exhibited disorder at the 2-carbon (C2) atom, and the structures for trans and cis isomers have been resolved crystallographically. 2(S)-Oxazolam forms polymeric chains with intermediation of ethanol through hydrogen bonding. 2(R)-Oxazolam crystallizes in space group P1, with cell dimensions a = 7.754(1) A, b = 8.654(1) A, c = 15.795(2) A, alpha = 104.09(1) degrees, beta = 91.19(1) degrees, and gamma = 114.00(1) degrees. A similar disorder at the C2 position has been elucidated by a mixture of trans- and cis-2(R)-oxazolams. The two 2(R)-oxazolam molecules form a dimer with a hydrogen bond net. The structural details, focusing on the conformation and molecular complex formation of both oxazolams, have been discussed in connection with the oxazolidine ring stability and the crystal polymorph.

Polyclonal antibodies to agonist benzodiazepines

Benzodiazepine-binding, immunoglobulin G class antibodies have been raised in three rabbits immunised with a conjugate of kenazepine coupled to keyhole limpet haemocyanin. The antibodies were assayed by [3H]flunitrazepam binding, followed by adsorption onto Staphylococcus aureus cells. Measurement of the rates of association and dissociation of [3H]flunitrazepam binding, together with saturation analysis of equilibrium binding, revealed varying degrees of heterogeneity in the affinity constants of the three rabbit antisera (equilibrium KD values 0.18 to 4.13 nM at 20-22 degrees). Specificity of the antibodies was investigated by testing a wide variety of compounds (at concentrations of up to 10-100 microM) for their ability to inhibit [3H]flunitrazepam binding. Only benzodiazepines known to act as agonists at their receptor sites in the central nervous system (CNS) caused an inhibition of binding. The rank orders of the IC50 values of these drugs for inhibition of [3H]flunitrazepam binding to IgG from two out of the three rabbits correlated significantly with that previously published for displacement of CNS receptor binding. The agonist beta-carboline derivative ZK 93423, the anxiolytic cyclopyrrolones suriclone and zopiclone and the purines inosine and hypoxanthine all failed to inhibit antibody binding, supporting previous suggestions that these drugs may bind at non-benzodiazepine recognition sites on the CNS receptor. The antibodies described are expected to provide useful reagents for raising anti-idiotypic antibodies directed against the CNS receptor and for the identification and purification of possible endogenous benzodiazepine receptor agonists in the CNS.