(E)-3-(2-(N-phenylcarbamoyl)vinyl)pyrrole-2-carboxylic acid derivatives. A novel class of glycine site antagonists

Synthesis, Antiviral Potency, in Vitro ADMET, and X-ray Structure of Potent CD4 Mimics as Entry Inhibitors That Target the Phe43 Cavity of HIV-1 gp120

In our attempt to optimize the lead HIV-1 entry antagonist, NBD-11021, we present in this study the rational design and synthesis of 60 new analogues and determination of their antiviral activity in a single-cycle and a multicycle infection assay to derive a comprehensive structure-activity relationship (SAR). Two of these compounds, NBD-14088 and NBD-14107, showed significant improvement in antiviral activity compared to the lead entry antagonist in a single-cycle assay against a large panel of Env-pseudotyped viruses. The X-ray structure of a similar compound, NBD-14010, confirmed the binding mode of the newly designed compounds. The in vitro ADMET profiles of these compounds are comparable to that of the most potent attachment inhibitor BMS-626529, a prodrug of which is currently undergoing phase III clinical trials. The systematic study presented here is expected to pave the way for improving the potency, toxicity, and ADMET profile of this series of compounds with the potential to be moved to the early preclinical development.

Drug design, in vitro pharmacology, and structure-activity relationships of 3-acylamino-2-aminopropionic acid derivatives, a novel class of partial agonists at the glycine site on the N-methyl-D-aspartate (NMDA) receptor complex

Retaining agonistic activity at the glycine coagonist site of the NMDA receptor in molecules derived from glycine or d-serine has proven to be difficult because in the vicinity of the alpha-amino acid group little substitution is tolerated. We have solved this problem by replacing the hydroxy group of d-serine with an amido group, thus keeping the hydrogen donor function and allowing for further substitution and exploration of the adjacent space. Heterocyclic substitutions resulted in a series of 3-acylamino-2-aminopropionic acid derivatives, with high affinities in a binding assay for the glycine site. In a functional assay assessing the activation of the glycine site, these compounds displayed a wide range of intrinsic efficacies, from antagonism to a high degree of partial agonism. Structure-activity relationships reveal that lipophilic substituents, presumably filling an additional hydrophobic pocket, are accepted by the glycine site, provided that they are separated from the alpha-amino acid group by a short linker.

Solvent-Free Thermal and Microwave-Assisted [3 + 2] Cycloadditions between Stabilized Azomethine Ylides and Nitrostyrenes. An Experimental and Theoretical Study

The stereochemical outcomes observed in the thermal and microwave-assisted [3 + 2] cycloaddition between stabilized azomethine ylides and nitrostyrenes have been analyzed using experimental and computational approaches. It has been observed that, in the absence of solvent, three stereoisomers are formed, both under classical heating conditions and under microwave irradiation. This result contrasts with that observed in solution under classical thermal conditions. The 4-nitropyrrolidines obtained in this way can be aromatized under further microwave irradiation to yield mixtures of pyrroles and 4-nitropyrroles. It is found that ground state cycloadditions between imines and nitrostyrenes take place by three-step mechanisms. The first step involves enolization of the starting imine, and this is followed by a pseudopericyclic 10-electron [1.4]-hydrogen shift. Finally, the cycloaddition takes place by a relatively asynchronous aromatic six-electron supra-supra thermal mechanism.

A modular synthesis of the lamellarins: total synthesis of lamellarin G trimethyl ether

A modular synthesis of the lamellarin family of natural products has been developed that is based on the application of three iterative halogenation/cross-coupling reaction sequences. The ability to halogenate the pyrrole core in a regioselective fashion, even in the presence of highly electron-rich aryl substituents, has been established. The compatibility of Suzuki coupling conditions with free alcohols and phenols in the boronic acids has been employed to reduce the number of protection/deprotection steps. Indeed, the presence of a free phenol on boronic acid 3 has been determined to be critical for the successful final coupling in route to lamellarin G trimethyl ether, since protected versions fail to undergo coupling.

Hydantoin-substituted 4,6-dichloroindole-2-carboxylic acids as ligands with high affinity for the glycine binding site of the NMDA receptor

A novel series of C-3 substituted 4,6-dichloroindole-2-carboxylic acids was synthesized to investigate the influence of different hydrogen-bond donor and acceptor groups at this specific position on the affinity to the glycine site of the NMDA receptor. These novel 3-indolylmethyl derivatives with ring-open (amines, sulfonamides, amides, ureas) and cyclic substituents (imidazolidin-2-ones, (thio)hydantoins) led to the discovery that compounds bearing a hydantoin substituent at the C-3 position of the indole nucleus are the most promising ones. In this series the hydantoins, ureas, and imidazolidin-2-ones were identified as very potent inhibitors of the binding of the glycine site specific ligand [(3)H]MDL 105,519 to pig cortical brain membranes. Since the hydantoins can be produced via a versatile synthetic approach, further amendments of the hydantoin-substituted compounds were conducted to elucidate the influence of aromatic and aliphatic moieties at position 3 of the hydantoin as well as of sterically hindered compounds (5-substituted hydantoins). On the basis of the pharmacological data obtained in displacement experiments with [(3)H]MDL 105,519 and the emerging structure-activity relationships, we confirm the existing pharmacophore model that suggests a hydrogen-bond acceptor and an aromatic substituent at position 3 of the indole as the key features for high affinity. Log P values indicate brain permeability and selected compounds showed anticonvulsant activity in vivo. Binding studies for the sodium channel (site 2) were also performed on some selected compounds.

From crystallographic data to the creation of a binding model with a receptor

The basic model for glycine receptor site has been proposed based on the ligands incorporated spatially inflexible main skeleton. The search for compounds, which are selectively bound to the receptor, is now based on topological and/or stereochemical requirements and restrictions derived for the glycine binding site. IsoStar is the definitive database of experimental and theoretical information on non-bonded interactions. It has been designed to play a prominent role in the field of rational drug design. We applied IsoStar in our search for the model of glycine binding site of the NMDA receptor.

Synthesis and pharmacological properties of novel glycine antagonists

The NMDA receptor is an ionotropic receptor complex widely distributed in the central nervous system and its activation, particularly in hypoxic conditions such as stroke, traumatic head injury and hypoglycemia, results in a massive influx of calcium ions into the post-synaptic neurones, leading to cell death through the activation of several neurotoxic cascades. The NMDA receptor is a unique ionotropic receptor complex because its activation requires the simultaneous binding of glutamate and glycine and selective antagonists at the glycine binding site are endowed with a better side-effect profile than competitive NMDA antagonists. Then, considerable efforts have been devoted to find potent and selective ligands, resulting in the identification of several classes of glycine antagonists. The research at Glaxo Wellcome has been aimed at the identification of novel in vivo active glycine antagonists, and led to the synthesis and pharmacological characterization of a number of novel, potent and systemically active compounds belonging to different chemical classes.

Statistical analysis on a series of glycine antagonists

Quantitative structure-activity relationships of two series of glycine antagonists, pyrido[2,3-b]pyrazines and pyrido[2,3-b]pyrazine N-oxides, was performed using PLS (Projection on Latent Variables) and traditional physico-chemical and topological descriptors. The effect of substitution on the heteroaromatic ring was investigated with the aim of further improving the affinity (expressed as pKi) of these derivatives towards the strychnine-insensitive glycine binding site associated with the NMDA receptor. A significant model was obtained for both series of compounds. Structure-activity implications are discussed.

Glycine-site antagonists and stroke

The excitatory amino acid, (S)-glutamic acid, plays an important role in controlling many neuronal processes. Its action is mediated by two main groups of receptors: the ionotropic receptors (which include NMDA, AMPA and kainic acid subtypes) and the metabotropic receptors (mGluR(1-8)) mediating G-protein coupled responses. This review focuses on the strychnine insensitive glycine binding site located on the NMDA receptor channel, and on the possible use of selective antagonists for the treatment of stroke. Stroke is a devastating disease caused by a sudden vascular accident. Neurochemically, a massive release of glutamate occurs in neuronal tissue; this overactivates the NMDA receptor, leading to increased intracellular calcium influx, which causes neuronal cell death through necrosis. NMDA receptor activation strongly depends upon the presence of glycine as a co-agonist. Therefore, the administration of a glycine antagonist can block overactivation of NMDA receptors, thus preserving neurones from damage. The glycine antagonists currently identified can be divided into five main categories depending on their chemical structure: indoles, tetrahydroquinolines, benzoazepines, quinoxalinediones and pyrida-zinoquinolines.

3-(2-Carbamoylvinyl)-4,5-dimethylpyrrole-2-carboxylic acids as ligands at the NMDA glycine-binding site: a study on the 2-carbamoylvinyl chain modification

Twenty 4,5-dimethylpyrrole-2-carboxylic acids (5a-t) with different 2-carbamoylvinyl chains in position 3 were prepared to further investigate the relationships between structure and in vitro affinity for the strychnine-insensitive glycine-binding site. None of these compounds was superior to (E)-3-(N-phenyl-2-carbamoylvinyl)-4,5-dimethylpyrrole-2-carb oxylic acid III (pKi = 6.70), which was taken as a reference standard, but overall the results obtained indicate that the N-phenyl-2-carbamoylvinyl substituent of III may be replaced with the N-(1-adamantyl)-2-carbamoylvinyl group as in 5h (pKi = 6.20) without considerable loss of affinity. This finding adds to previous knowledge.