Diaryl substituted pyrrolidinones and pyrrolones as 5-HT2C inhibitors: Synthesis and biological evaluation

Unusual Regio- and Chemoselectivity in Oxidation of Pyrroles and Indoles Enabled by a Thianthrenium Salt Intermediate

A dearomative oxidation of pyrroles to Δ3-pyrrol-2-ones is described, which employs a sulfoxide as oxidant, in conjunction with a carboxylic acid anhydride and a Brønsted acid additive. 3-substituted pyrroles undergo regioselective oxidation to give the product isomer in which oxygen has been introduced at the more hindered position. Regioselectivity is rationalized by a proposed mechanism that proceeds by initial thianthrenium introduction at the less-hindered pyrrole α-position, followed by distal attack of an oxygen nucleophile and subsequent elimination of thianthrene. The same reaction conditions are also able to effect a chemoselective oxidation of indoles to indolin-3-ones and additionally of indolin-3-ones to 2-hydroxyindolin-3-ones. Here again, the regio- and chemoselectivities are rationalized through the intermediacy of a thianthrenium salt.

The Recycling of Substandard Rocket Fuel N,N-Dimethylhydrazine via the Involvement of Its Hydrazones Derived from Glyoxal, Acrolein, Metacrolein, Crotonaldehyde, and Formaldehyde in Organic Synthesis

"Heptil" (unsymmetrical dimethylhydrazine-UDMH) is extensively employed worldwide as a propellant for rocket engines. However, UDMH constantly loses its properties as a result of its continuous and uncontrolled absorption of moisture, which cannot be rectified. This situation threatens its long-term usability. UDMH is an exceedingly toxic compound (Hazard Class 1), which complicates its transportation and disposal. Incineration is currently the only method used for its disposal, but this process generates oxidation by-products that are even more toxic than the original UDMH. A more benign approach involves its immediate reaction with a formalin solution to form 1,1-dimethyl-2-methylene hydrazone (MDH), which is significantly less toxic by an order of magnitude. MDH can then be polymerized under acidic conditions, and the resulting product can be burned, yielding substantial amounts of nitrogen oxides. This review seeks to shift the focus of MDH from incineration towards its application in the synthesis of relatively non-toxic and readily available analogs of various pharmaceutical substances. We aim to bring the attention of the international chemical community to the distinctive properties of MDH, as well as other hydrazones (such as glyoxal, acrolein, crotonal, and meta-crolyl), wherein each structural fragment can initiate unique transformations that have potential applications in molecular design, pharmaceutical research, and medicinal chemistry.

Treatment of Substandard Rocket Fuel 1,1-Dimethylhydrazine via Its Methylene Derivative into Heterocycles Based on Pyrrolo-[3,4c]Quinolines, Cyclododeca[b]piran and Pyrrole

1,1-Dimethylhydrazine (Heptil, rocket fuel (UDMH)) is characterized by extremely high toxicity, teratogenicity and the ability to constantly absorb water from the atmosphere, losing its energy characteristics. In this regard, as well as due to the alternative fuel ("Angara") transition, there is a need for UDMH utilization in huge amounts. A more benign approach involves its immediate reaction with a formalin solution to form 1,1-dimethyl-2-methylene hydrazone (MDH), which is significantly less toxic by an order of magnitude. MDH can then be polymerized under acidic conditions, and the resulting product can be burned, yielding a substantial amount of nitrogen oxides. We propose an alternative to incineration by involving MDH in organic synthesis. We studied the reactions of MDH and its analog N,N-dimethyl-2-(methylenamino)ethane-1-amine (MDEA) with available CH-acids: tetracyanoethylated ketones (TCEKs) based on cyclohexanone, 4-propylcyclohexanone, 2-methylcyclohexanone, cyclododecanone and tetracyanoethane. The structures synthesized were confirmed by IR, 1H, 13C NMR and mass spectroscopy methods. MDH-based adducts were also identified by X-ray structural analysis. TCEKs and MDH, as well as TCEK based on cyclohexanone and MDEA, form bi- and tricyclic structures: pyrrolo [3,4c]-quinolines (using TCEKs based on cyclohexanone and 4-propylcyclohexanone), epiminomethanoquinoline-3,4-dicarbonitrile (using TCEK based on 2-methylcyclohexanone) and cyclododec[b]pyran-3,4-dicarbonitrile (using TCEK based on cyclododecanone). MDH and TCNEH2 formed a pyrrole derivative. Thus, we synthesized the structures that are of interest for molecular design and pharmaceutical chemistry.

Cyclization of N-Boc-(E)-α,β-unsaturated γ-amino acid active esters into N-Boc-(Z)-α,β-unsaturated γ-lactams through E → Z isomerization

Here, we are reporting the spontaneous transformation of the active esters of N-Boc protected E-α,β-unsaturated γ-amino acids into the corresponding Z-α,β-unsaturated γ-lactams with concomitant E → Z isomerization in the presence of a weak base. No cyclization was observed in the absence of the base. Analysis revealed that amide γ-NH is crucial for both lactamization and E → Z isomerization. This mild transformation provides easy access to the synthetically challenging α,β-unsaturated γ-lactams and also gives new insights into the E → Z isomerization of double bonds.

Excited-State Copper-Catalyzed [4 + 1] Annulation Reaction Enables Modular Synthesis of α,β-Unsaturated-γ-Lactams

Synthesis of α,β-unsaturated-γ-lactams continue to attract attention due to the importance of this structural motif in organic chemistry. Herein, we report the development of a visible-light-induced excited-state copper-catalyzed [4 + 1] annulation reaction for the preparation of a wide range of γ-H, -OH, and -OR-substituted α,β-unsaturated-γ-lactams using acrylamides as the 4-atom unit and aroyl chlorides as the 1-atom unit. This modular synthetic protocol features mild reaction conditions, broad substrate scope, and high functional group tolerance. The reaction is amenable to late-stage diversification of complex molecular architectures, including derivatives of marketed drugs. The products of the reaction can serve as versatile building blocks for further derivatization. Preliminary mechanistic studies suggest an inner-sphere catalytic cycle involving photoexcitation of the Cu(BINAP) catalyst, single-electron transfer, and capture of radical intermediates by copper species, followed by reductive elimination or protonation to give the desired γ-functionalized α,β-unsaturated-γ-lactams.

Domino Synthesis of α,β-Unsaturated γ-Lactams by Stereoselective Amination of α-Tertiary Allylic Alcohols

Tertiary allylic alcohols equipped with a carboxyl group can be smoothly aminated under ambient conditions by a conceptually new and stereoselective protocol under palladium catalysis. The in situ formed Z-configured γ-amino acid cyclizes to afford an α,β-unsaturated γ-lactam, releasing water as the only byproduct. This practical catalytic transformation highlights the use of a carboxyl group acting as an activating and stereodirecting functional group to provide a wide series of pharma-relevant building blocks. Various control reactions support the crucial role of the carboxyl group in the substrate to mediate these transformations.

Synthesis, bioactivity, 3D-QSAR studies of novel dibenzofuran derivatives as PTP-MEG2 inhibitors

PTP-MEG2 plays a critical role in the diverse cell signalling processes, so targeting PTP-MEG2 is a promising strategy for various human diseases treatments. In this study, a series of novel dibenzofuran derivatives was synthesized and assayed for their PTP-MEG2 inhibitory activities. 10a with highest inhibitory activity (320 nM) exhibited significant selectivity for PTP-MEG2 over its close homolog SHP2, CDC25 (IC₅₀ > 50 μM). By means of the powerful “HipHop” technique, a 3D-QSAR study was carried out to explore structure activity relationship of these molecules. The generated pharmacophore model revealed that the one RA, three Hyd, and two HBA features play an important role in binding to the active site of the target protein-PTP-MEG2. Docking simulation study indicated that 10a achieved its potency and specificity for PTP-MEG2 by targeting unique nearby peripheral binding pockets and the active site. The absorption, distribution, metabolism and excretion (ADME) predictions showed that the 11 compounds hold high potential to be novel lead compounds for targeting PTP-MEG2. Our findings here can provide a new strategy or useful insights for designing the effective PTP-MEG2 inhibitors.

Visible light dye-photosensitised oxidation of pyrroles using a simple LED photoreactor

The photooxidation of pyrrole is typically low yielding due to the absorbance of ultraviolet light, which leads to uncontrolled polymerisation and decomposition. Presented herein is the development of a simple and cost-effective photoreactor utilising Light Emitting Diodes (LEDs) as the light source, and its application to the dye-sensitised oxidation of a range of pyrroles to give corresponding 3-pyrrolin-2-ones. The broader applicability of this approach to the generation of ¹O₂ is also explored.

Computational methods for the discovery of mood disorder therapies

INTRODUCTION

Despite the significant progress, research is still needed to reveal details of the complex and dynamic chemical processes operating in the central nervous system (CNS) and their relationship to psychological effects such as mood disorders. The incidence of behavioral depression is widely spread worldwide, with an estimated 14.8 million adults diagnosed yearly in the United States alone. The efficacy of current antidepressants on 50 - 60% of patients, their slow onset of action and the prevalence of adverse side effects highlight the need for developing a new generation of improved antidepressants. Computational methods have the potential to aid in the discovery of mood modulators.

AREAS COVERED

This review contains three main sections: historical evolution of marketed antidepressants, physicochemical and structural properties of antidepressant compounds reported in the ChEMBL database and recent efforts in the design and discovery of antidepressants using computational methods. The authors provide details of the computational methods employed, from chemoinformatic analyses to molecular modeling.

EXPERT OPINION

While there have been numerous and important findings in depression research, the high cost and time spent on research into new therapies for brain disorders is a risky undertaking. Computational methodologies can be employed to speed up the discovery of new antidepressants and to detect new sources of chemical compounds with potential antidepressant activity. Compound collections containing compounds already approved in the pharmaceutical and food industries that cover the property space and complement the structural space of CNS drugs represent a promising starting point for the discovery of new antidepressant agents.

Insights into binding modes of 5-HT2c receptor antagonists with ligand-based and receptor-based methods

5-hydroxytryptamine-2c (5-HT2c) receptor antagonists have clinical utility in the management of nervous system. In this work, ligand-based and receptor-based methods were used to investigate the binding mode of h5-HT2c receptor antagonists. First, the pharmacophore modeling of the h5-HT2c receptor antagonists was carried out by CATALYST. Then, the h5-HT2c antagonists were docked to the h5-HT2c receptor model. Subsequently, the comprehensive analysis of the pharmacophore and docking results revealed the structure-activity relationship of 5-HT2c receptor antagonists and the key residues involved in the interactions. For example, three hydrophobic points in the ligands corresponded to the region surrounded by Val135, Val208, Phe214, Ala222, Phe327, Phe328 and Val354 of the h5-HT2c receptor. The carbonyl group of compound 1 formed a hydrogen bond with Asn331. The nitrogen atom in the piperidine of compound 1 corresponding to the positive ionizable position of the best pharmacophore formed the electrostatic interactions with the carbonyl of Asp134, Asn331 and Val354, and with the hydroxyl group of Ser334. In addition, a predictive CoMFA model was developed based on the 24 compounds that were used as the training set in the pharmacophore modeling. Our results were not only useful to explore the detailed mechanism of the interactions between the h5-HT2c receptor and antagonists, but also provided suggestions in the discovery of novel 5-HT2c receptor antagonists.

Feasible Synthesis of Antagonist of GPR40 by Constructing 2-Thiouracil Ring viaAcid Mediated Cyclization

GW1100 is an antagonist of GPR40 identified by high throughput screening recently. The synthesis of GW1100 has been developed. The key step involves cyclization of the 2-thiouracil heterocycle under acidic condition at room temperature.

Isoindolone derivatives, a new class of 5-HT2C antagonists: Synthesis and biological evaluation

Two independent approaches resulted in the identification of a series of isoindolone derivatives as potent and selective 5-HT2C antagonists. From a Medicinal Chemistry perspective this template was considered interesting as it allowed the incorporation of the carbon-carbon double bond of an earlier dihydropyrrolone series in an aromatic system within a comparatively simple and compact motif. Additionally an in silico screening approach of the corporate database using a 5-HT2C pharmacophore model resulted in the identification of a related structure containing this template. The strategy used to optimise potency at the target receptor and to improve the pharmacokinetic profile is described, resulting in molecules combining high potency with good selectivity and oral bioavailability.

5-HT2C antagonists based on fused heterotricyclic templates: design, synthesis and biological evaluation

Design, synthesis and properties of a new tricyclic series of selective 5-HT2C receptor antagonists are reported. Conformational analysis of a 2-phenyl-dihydropyrrolone scaffold suggested that ring fusion, locking coplanarity between the rings of this moiety, might be tolerated by the 5-HT2C receptor. An interesting effect of this is the change of the nature of the carbon-carbon double bond of the lactam ring from vinylic to aromatic. The changes were found to result in a favourable profile at both, receptor and in vivo level.