ADME-guided design and synthesis of aryloxanyl pyrazolone derivatives to block mutant superoxide dismutase 1 (SOD1) cytotoxicity and protein aggregation: potential application for the treatment of amyotrophic lateral sclerosis

Current therapy in amyotrophic lateral sclerosis (ALS): A review on past and future therapeutic strategies

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the first and second motoneurons (MNs), associated with muscle weakness, paralysis and finally death. The exact etiology of the disease still remains unclear. Currently, efforts to develop novel ALS treatments which target specific pathomechanisms are being studied. The mechanisms of ALS pathogenesis involve multiple factors, such as protein aggregation, glutamate excitotoxicity, oxidative stress, mitochondrial dysfunction, apoptosis, inflammation etc. Unfortunately, to date, there are only two FDA-approved drugs for ALS, riluzole and edavarone, without curative treatment for ALS. Herein, we give an overview of the many pathways and review the recent discovery and preclinical characterization of neuroprotective compounds. Meanwhile, drug combination and other therapeutic approaches are also reviewed. In the last part, we analyze the reasons of clinical failure and propose perspective on the treatment of ALS in the future.

Proteasome activation: A novel strategy for targeting undruggable intrinsically disordered proteins

Intrinsically disordered proteins (IDPs) are characterized by their inability to adopt well-defined tertiary structures under physiological conditions. Nonetheless, they often play pivotal roles in the progression of various diseases, including cancer, neurodegenerative disorders, and cardiovascular ailments. Owing to their inherent dynamism, conventional drug design approaches based on structural considerations encounter substantial challenges when applied to IDPs. Consequently, the pursuit of therapeutic interventions directed towards IDPs presents a complex endeavor. While there are indeed existing methodologies for targeting IDPs, they are encumbered by noteworthy constrains. Hence, there exists an imminent imperative to investigate more efficacious and universally applicable strategies for modulating IDPs. Here, we present an overview of the latest advancements in the research pertaining to IDPs, along with the indirect regulation approach involving the modulation of IDP degradation through proteasome. By comprehending these advancements in research, novel insights can be generated to facilitate the development of new drugs targeted at addressing the accumulation of IDPs in diverse pathological conditions.

Proteasome localization and activity in pig brain and in vivo small molecule screening for activators

Introduction

Loss of proteasome function, proteinopathy, and proteotoxicity may cause neurodegeneration across the human lifespan in several forms of brain injury and disease. Drugs that activate brain proteasomes in vivo could thus have a broad therapeutic impact in neurology.

Methods

Using pigs, a clinically relevant large animal with a functionally compartmental gyrencephalic cerebral cortex, we evaluated the localization and biochemical activity of brain proteasomes and tested the ability of small molecules to activate brain proteasomes.

Results

By Western blotting, proteasome protein subunit PSMB5 and PSMA3 levels were similar in different pig brain regions. Immunohistochemistry for PSMB5 showed localization in the cytoplasm (diffuse and particulate) and nucleus (cytoplasm < nucleus). Some PSMB5 immunoreactivity was colocalized with mitochondrial (voltage-gated anion channel and cyclophilin D) and cell death (Aven) proteins in the neuronal soma and neuropil in the neocortex of pig and human brains. In the nucleus, PSMB5 immunoreactivity was diffuse, particulate, and clustered, including perinucleolar decorations. By fluorogenic assay, proteasome chymotrypsin-like activities (CTL) in crude tissue soluble fractions were generally similar within eight different pig brain regions. Proteasome CTL activity in the hippocampus was correlated with activity in nasal mucosa biopsies. In pilot analyses of subcellular fractions of pig cerebral cortex, proteasome CTL activity was highest in the cytosol and then ~50% lower in nuclear fractions; ~15-20% of total CTL activity was in pure mitochondrial fractions. With in-gel activity assay, 26S-singly and -doubly capped proteasomes were the dominant forms in the pig cerebral cortex. With a novel in situ histochemical activity assay, MG132-inhibitable proteasome CTL activity was localized to the neuropil, as a mosaic, and to cell bodies, nuclei, and centrosome-like perinuclear satellites. In piglets treated intravenously with pyrazolone derivative and chlorpromazine over 24 h, brain proteasome CTL activity was modestly increased.

Discussion

This study shows that the proteasome in the pig brain has relative regional uniformity, prominent nuclear and perinuclear presence with catalytic activity, a mitochondrial association with activity, 26S-single cap dominance, and indications from small molecule systemic administration of pyrazolone derivative and chlorpromazine that brain proteasome function appears safely activable.

Small molecules targeting different cellular pathologies for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease in which the motor neuron circuitry displays progressive degeneration, affecting mostly the motor neurons in the brain and in the spinal cord. There are no effective cures, albeit three drugs, riluzole, edaravone, and AMX0035 (a combination of sodium phenylbutyrate and taurursodiol), have been approved by the Food and Drug Administration, with limited improvement in patients. There is an urgent need to build better and more effective treatment strategies for ALS. Since the disease is very heterogenous, numerous approaches have been explored, such as targeting genetic mutations, decreasing oxidative stress and excitotoxicity, enhancing mitochondrial function and protein degradation mechanisms, and inhibiting neuroinflammation. In addition, various chemical libraries or previously identified drugs have been screened for potential repurposing in the treatment of ALS. Here, we review previous drug discovery efforts targeting a variety of cellular pathologies that occur from genetic mutations that cause ALS, such as mutations in SOD1, C9orf72, FUS, and TARDP-43 genes. These mutations result in protein aggregation, which causes neuronal degeneration. Compounds used to target cellular pathologies that stem from these mutations are discussed and comparisons among different preclinical models are presented. Because the drug discovery landscape for ALS and other motor neuron diseases is changing rapidly, we also offer recommendations for a novel, more effective, direction in ALS drug discovery that could accelerate translation of effective compounds from animals to patients.

Molecular mechanisms of amyotrophic lateral sclerosis as broad therapeutic targets for gene therapy applications utilizing adeno-associated viral vectors

Despite the devastating clinical outcome of the neurodegenerative disease, amyotrophic lateral sclerosis (ALS), its etiology remains mysterious. Approximately 90% of ALS is characterized as sporadic, signifying that the patient has no family history of the disease. The development of an impactful disease modifying therapy across the ALS spectrum has remained out of grasp, largely due to the poorly understood mechanisms of disease onset and progression. Currently, ALS is invariably fatal and rapidly progressive. It is hypothesized that multiple factors can lead to the development of ALS, however, treatments are often focused on targeting specific familial forms of the disease (10% of total cases). There is a strong need to develop disease modifying treatments for ALS that can be effective across the full ALS spectrum of familial and sporadic cases. Although the onset of disease varies significantly between patients, there are general disease mechanisms and progressions that can be seen broadly across ALS patients. Therefore, this review explores the targeting of these widespread disease mechanisms as possible areas for therapeutic intervention to treat ALS broadly. In particular, this review will focus on targeting mechanisms of defective protein homeostasis and RNA processing, which are both increasingly recognized as design principles of ALS pathogenesis. Additionally, this review will explore the benefits of gene therapy as an approach to treating ALS, specifically focusing on the use of adeno-associated virus (AAV) as a vector for gene delivery to the CNS and recent advances in the field.

A chemogenomic approach is required for effective treatment of amyotrophic lateral sclerosis

ALS is a fatal untreatable disease involving degeneration of motor neurons. Μultiple causative genes encoding proteins with versatile functions have been identified indicating that diverse biological pathways lead to ALS. Chemical entities still represent a promising choice to delay ALS progression, attenuate symptoms and/or increase life expectancy, but also gene-based and stem cell-based therapies are in the process of development, and some are tested in clinical trials. Various compounds proved effective in transgenic models overexpressing distinct ALS causative genes unfortunately though, they showed no efficacy in clinical trials. Notably, while animal models provide a uniform genetic background for preclinical testing, ALS patients are not stratified, and the distinct genetic forms of ALS are treated as one group, which could explain the observed discrepancies between treating genetically homogeneous mice and quite heterogeneous patient cohorts. We suggest that chemical entity-genotype correlation should be exploited to guide patient stratification for pharmacotherapy, that is administered drugs should be selected based on the ALS genetic background.

Investigation of stable solid diazonium salt by molecular structure, Hirshfeld surface analysis, optical and electrochemical studies, and applications

The title compound is a new pyrazolone derivative which was synthesized starting from p-sulphophenyl-3-methyl-5-pyrazolone (1) by nitrosation at low temperature to afford the corresponding p-sulphophenyl-3-methyl-4-nitroso-5-pyrazolone which can exist both in nitroso (2a) and oxime tautomeric forms (2b). Reduction of the latter using zinc with hydrochloric acid furnished the 4-amino-p-sulphophenyl-3-methyl-5-pyrazolone (3). The diazotization of (3) under careful control of temperature and pH afforded the p-sulphophenyl-3-methyl-5-pyrazolone diazonium salt (4) which was re-crystallized from acidified ethanol to afford crystal suitable for X-ray studies. UV-visible spectrum and cyclic voltammetric studies were also carried out indicating λ_max at 420 nm and HOMO-LUMMO energy gap was also calculated (E_g) of 2.95 eV. The molecular and crystal structures of the compound were clarified by single crystal X-ray diffraction indicated that it crystallizes as the sodium salt in the triclinic space group P -1, with the 4-azo-pyrazolone and the sulphophenyl groups being nearly coplanar. To get an insight to the intermolecular interactions in the crystal, a Hirshfeld surface analysis was also carried out.

Classification models and SAR analysis on CysLT1 receptor antagonists using machine learning algorithms

Cysteinyl leukotrienes 1 (CysLT1) receptor is a promising drug target for rhinitis or other allergic diseases. In our study, we built classification models to predict bioactivities of CysLT1 receptor antagonists. We built a dataset with 503 CysLT1 receptor antagonists which were divided into two groups: highly active molecules (IC₅₀ < 1000 nM) and weakly active molecules (IC₅₀ ≥ 1000 nM). The molecules were characterized by several descriptors including CORINA descriptors, MACCS fingerprints, Morgan fingerprint and molecular SMILES. For CORINA descriptors and two types of fingerprints, we used the random forests (RF) and deep neural networks (DNN) to build models. For molecular SMILES, we used recurrent neural networks (RNN) with the self-attention to build models. The accuracies of test sets for all models reached 85%, and the accuracy of the best model (Model 2C) was 93%. In addition, we made structure-activity relationship (SAR) analyses on CysLT1 receptor antagonists, which were based on the output from the random forest models and RNN model. It was found that highly active antagonists usually contained the common substructures such as tetrazoles, indoles and quinolines. These substructures may improve the bioactivity of the CysLT1 receptor antagonists.

Pyrazolone structural motif in medicinal chemistry: Retrospect and prospect

The pyrazolone structural motif is a critical element of drugs aimed at different biological end-points. Medicinal chemistry researches have synthesized drug-like pyrazolone candidates with several medicinal features including antimicrobial, antitumor, CNS (central nervous system) effect, anti-inflammatory activities and so on. Meanwhile, SAR (Structure-Activity Relationship) investigations have drawn attentions among medicinal chemists, along with a plenty of analogues have been derived for multiple targets. In this review, we comprehensively summarize the biological activity and SAR for pyrazolone analogues, wishing to give an overall retrospect and prospect on the pyrazolone derivatives.

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The pyrazolone structural motif is a critical element of drugs aimed at different biological end-points.

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The pyrazolone analogues have been carried out to drug-like candidates with broad range of medicinal properties.

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This review wishes to give an overall retrospect and prospect on the pyrazolone derivatives.

Proteasome Activation as a New Therapeutic Approach To Target Proteotoxic Disorders

Proteasomes are multienzyme complexes that maintain protein homeostasis (proteostasis) and important cellular functions through the degradation of misfolded, redundant, and damaged proteins. It is well established that aging is associated with the accumulation of damaged and misfolded proteins. This phenomenon is paralleled by declined proteasome activity. When the accumulation of redundant proteins exceed degradation, undesirable signaling and/or aggregation occurs and are the hallmarks of neurodegenerative diseases and many cancers. Thus, increasing proteasome activity has been recognized as a new approach to delay the onset or ameliorate the symptoms of neurodegenerative and other proteotoxic disorders. Enhancement of proteasome activity has many therapeutic potentials but is still a relatively unexplored field. In this perspective, we review current approaches, genetic manipulation, posttranslational modification, and small molecule proteasome agonists used to increase proteasome activity, challenges facing the field, and applications beyond aging and neurodegenerative diseases.

CNS repurposing - Potential new uses for old drugs: Examples of screens for Alzheimer's disease, Parkinson's disease and spasticity

Drug repurposing is recently gaining increasing attention, not just from pharmaceutical companies but also from government agencies in an attempt to generate new medications to address increasing unmet medical needs in a cost effective and expedite manner. There are several approaches to identify novel indications for known drugs. Many are based on rational selection e.g. the known or a new mechanism of action of a drug. This review will focus rather on phenotypic or high content screening of compounds in models that are believed to be predictive of effectiveness of compounds irrespective of their mechanism of action. Three short cases studies of screens for Alzheimer's disease, Parkinson's disease and spasticity will be given as examples. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

A computational combinatorial approach identifies a protein inhibitor of superoxide dismutase 1 misfolding, aggregation, and cytotoxicity

Molecular agents that specifically bind and neutralize misfolded and toxic superoxide dismutase 1 (SOD1) mutant proteins may find application in attenuating the disease progression of familial amyotrophic lateral sclerosis. However, high structural similarities between the wild-type and mutant SOD1 proteins limit the utility of this approach. Here we addressed this challenge by converting a promiscuous natural human IgG-binding domain, the hyperthermophilic variant of protein G (HTB1), into a highly specific aggregation inhibitor (designated HTB1_M) of two familial amyotrophic lateral sclerosis-linked SOD1 mutants, SOD1^G93A and SOD1^G85R We utilized a computational algorithm for mapping protein surfaces predisposed to HTB1 intermolecular interactions to construct a focused HTB1 library, complemented with an experimental platform based on yeast surface display for affinity and specificity screening. HTB1_M displayed high binding specificity toward SOD1 mutants, inhibited their amyloid aggregation in vitro, prevented the accumulation of misfolded proteins in living cells, and reduced the cytotoxicity of SOD1^G93A expressed in motor neuron-like cells. Competition assays and molecular docking simulations suggested that HTB1_M binds to SOD1 via both its α-helical and β-sheet domains at the native dimer interface that becomes exposed upon mutated SOD1 misfolding and monomerization. Our results demonstrate the utility of computational mapping of the protein-protein interaction potential for designing focused protein libraries to be used in directed evolution. They also provide new insight into the mechanism of conversion of broad-spectrum immunoglobulin-binding proteins, such as HTB1, into target-specific proteins, thereby paving the way for the development of new selective drugs targeting the amyloidogenic proteins implicated in a variety of human diseases.

Protein Homeostasis in Amyotrophic Lateral Sclerosis: Therapeutic Opportunities?

Protein homeostasis (proteostasis), the correct balance between production and degradation of proteins, is essential for the health and survival of cells. Proteostasis requires an intricate network of protein quality control pathways (the proteostasis network) that work to prevent protein aggregation and maintain proteome health throughout the lifespan of the cell. Collapse of proteostasis has been implicated in the etiology of a number of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), the most common adult onset motor neuron disorder. Here, we review the evidence linking dysfunctional proteostasis to the etiology of ALS and discuss how ALS-associated insults affect the proteostasis network. Finally, we discuss the potential therapeutic benefit of proteostasis network modulation in ALS.

Current Therapy of Drugs in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS), commonly termed as motor neuron disease (MND) in UK, is a chronically lethal disorder among the neurodegenerative diseases, meanwhile. ALS is basically irreversible and progressive deterioration of upper and lower motor neurons in the motor cortex, brain stem and medulla spinalis. Riluzole, used for the treatment of ALS, was demonstrated to slightly delay the initiation of respiratory dysfunction and extend the median survival of patients by a few months. In this study, the key biochemical defects were discussed, such as: mutant Cu/Zn superoxide dismutase, mitochondrial protectants, and anti-excitotoxic/ anti-oxidative / anti-inflammatory/ anti-apoptotic agents, so the related drug candidates that have been studied in ALS models would possibly be further used in ALS patients.

Optimizing Oral Bioavailability in Drug Discovery: An Overview of Design and Testing Strategies and Formulation Options

For discovery teams working toward new, orally administered therapeutic agents, one requirement is to attain adequate systemic exposure after oral dosing, which is best accomplished when oral bioavailability is optimized. This report summarizes the bioavailability challenges currently faced in drug discovery, and the design and testing methods and strategies currently utilized to address the challenges. Profiling of discovery compounds usually includes separate assessments of solubility, permeability, and susceptibility to first-pass metabolism, which are the 3 most likely contributors to incomplete oral bioavailability. An initial assessment of absorption potential may be made computationally, and high throughput in vitro assays are typically performed to prioritize compounds for in vivo studies. The initial pharmacokinetic study is a critical decision point in compound evaluation, and the importance of the effect the dosing vehicle or formulation can have on oral bioavailability, especially for poorly water soluble compounds, is emphasized. Dosing vehicles and bioavailability-enabling formulations that can be used for discovery and preclinical studies are described. Optimizing oral bioavailability within a chemical series or for a lead compound requires identification of the barrier limiting bioavailability, and methods used for this purpose are outlined. Finally, a few key guidelines are offered for consideration when facing the challenges of optimizing oral bioavailability in drug discovery.

Tertiary Amine Pyrazolones and Their Salts as Inhibitors of Mutant Superoxide Dismutase 1-Dependent Protein Aggregation for the Treatment of Amyotrophic Lateral Sclerosis

Pyrazolone derivatives have previously been found to be inhibitors of Cu/Zn superoxide dismutase 1 (SOD1)-dependent protein aggregation, which extended survival of an amyotrophic lateral sclerosis (ALS) mouse model. On the basis of ADME analysis, we describe herein a new series of tertiary amine-containing pyrazolones and their structure-activity relationships. Further conversion to the conjugate salts greatly improved their solubility. Phosphate compound 17 exhibited numerous benefits both to cellular activity and to CNS-related drug-like properties in vitro and in vivo, including microsomal stability, tolerated toxicity, and blood-brain barrier permeation. These results indicate that tertiary amine pyrazolones comprise a valuable class of ALS drug candidates.

Proteasome activation is a mechanism for pyrazolone small molecules displaying therapeutic potential in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and ultimately fatal neurodegenerative disease. Pyrazolone containing small molecules have shown significant disease attenuating efficacy in cellular and murine models of ALS. Pyrazolone based affinity probes were synthesized to identify high affinity binding partners and ascertain a potential biological mode of action. Probes were confirmed to be neuroprotective in PC12-SOD1^G93A cells. PC12-SOD1^G93A cell lysates were used for protein pull-down, affinity purification, and subsequent proteomic analysis using LC-MS/MS. Proteomics identified the 26S proteasome regulatory subunit 4 (PSMC1), 26S proteasome regulatory subunit 6B (PSMC4), and T-complex protein 1 (TCP-1) as putative protein targets. Coincubation with appropriate competitors confirmed the authenticity of the proteomics results. Activation of the proteasome by pyrazolones was demonstrated in the absence of exogenous proteasome inhibitor and by restoration of cellular protein degradation of a fluorogenic proteasome substrate in PC12-SOD1^G93A cells. Importantly, supplementary studies indicated that these molecules do not induce a heat shock response. We propose that pyrazolones represent a rare class of molecules that enhance proteasomal activation in the absence of a heat shock response and may have therapeutic potential in ALS.

Crystal structure of ethyl 2-({[(4Z)-3,5-dioxo-1-phenyl-pyrazolidin-4-yl-idene]meth-yl}amino)-acetate

The title compound, C14H15N3O4, is nearly planar, the dihedral angle between the planes of the phenyl and pyrazolidine rings being 1.13 (7) Å, and that between the plane of the pyrazolidine ring and the mean plane of the side chain [C-N-C-C(=O)-O; r.m.s. deviation = 0.024 Å] being 2.52 (7)°. This is due in large part to the presence of the intra-molecular N-H⋯O and C-H⋯O hydrogen bonds. In the crystal, pairwise N-H⋯O hydrogen bonds form inversion dimers, which are further associated into layers, lying very close to plane (-120), via pairwise C-H⋯O hydrogen bonds. The layers are then weakly connected through C-H⋯O hydrogen bonds, forming a three-dimensional structure.

Rodent models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by the degeneration of upper and lower motor neurons. Recent advances in our understanding of some of the genetic causes of ALS, such as mutations in SOD1, TARDBP, FUS and VCP have led to the generation of rodent models of the disease, as a strategy to help our understanding of the pathophysiology of ALS and to assist in the development of therapeutic strategies. This review provides detailed descriptions of TDP-43, FUS and VCP models of ALS, and summarises potential therapeutics which have been recently trialled in rodent models of the disease. This article is part of a Special Issue entitled: Animal Models of Disease.

Synthesis of some novel 4-arylidene pyrazoles as potential antimicrobial agents

BACKGROUND

Pyrazole and pyrazolone motifs are well known for their wide range of biological activities such as antimicrobial, anti-inflammatory, and antitumor activities. The incorporation of more than one pharmacophore in a single scaffold is a well known approach for the development of more potent drugs. In the present investigation, a series of differently substituted 4-arylidene pyrazole derivatives bearing pyrazole and pyrazolone pharmacophores in a single scaffold was synthesized.

RESULTS

The synthesis of novel 4-arylidene pyrazole compounds is achieved through Knovenagel condensation between 1,3-diaryl-4-formylpyrazoles and 3-methyl-1-phenyl-1H-pyrazol-5-(4H)-ones in good yields. All compounds were evaluated for their in vitro antimicrobial activity.

CONCLUSIONS

A series of 4-arylidene pyrazole derivatives was evaluated for their in vitro antimicrobial activity against two Gram-positive (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative bacteria (Pseudomonas fluorescens and Escherichia coli), as well as two pathogenic fungal strains (Candida albicans and Saccharomyces cerevisiae). The majority of the compounds displayed excellent antimicrobial profile against the Gram-positive (B. subtilis and S. aureus), and some of them are even more potent than the reference drug ciprofloxacin.

Design and synthesis of N-alkyldeoxynojirimycin derivatives with improved metabolic stability as inhibitors of BVDV and Tacaribe virus

Novel N-alkyldeoxynojirimycins (NADNJs) based on our previous lead 3 were designed, synthesized and tested in metabolic assays and in virus cultures. NADNJs containing terminal tertiary benzamide, sulfonamide, urea, and oxazolidinone moieties were discovered to have improved metabolic stability compared to 3, while maintaining submicromolar EC50 against BVDV and Tacaribe virus; and low cytotoxicity.

Recent progress in the discovery of small molecules for the treatment of amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with few therapeutic options. While several gene mutations have been implicated in ALS, the exact cause of neuronal dysfunction is unknown and motor neurons of affected individuals display numerous cellular abnormalities. Ongoing efforts to develop novel ALS treatments involve the identification of small molecules targeting specific mechanisms of neuronal pathology, including glutamate excitotoxicity, mutant protein aggregation, endoplasmic reticulum (ER) stress, loss of trophic factors, oxidative stress, or neuroinflammation. Herein, we review recent advances in the discovery and preclinical characterization of lead compounds that may ultimately provide novel drugs to treat patients suffering from ALS.

Arylazanylpyrazolone derivatives as inhibitors of mutant superoxide dismutase 1 dependent protein aggregation for the treatment of amyotrophic lateral sclerosis

The arylsulfanylpyrazolone and aryloxanylpyrazolone scaffolds previously were reported to inhibit Cu/Zn superoxide dismutase 1 dependent protein aggregation and to extend survival in the ALS mouse model. However, further evaluation of these compounds indicated weak pharmacokinetic properties and a relatively low maximum tolerated dose. On the basis of an ADME analysis, a new series of compounds, the arylazanylpyrazolones, has been synthesized, and structure-activity relationships were determined. The SAR results showed that the pyrazolone ring is critical to cellular protection. The NMR, IR, and computational analyses suggest that phenol-type tautomers of the pyrazolone ring are the active pharmacophore with the arylazanylpyrazolone analogues. A comparison of experimental and calculated IR spectra is shown to be a valuable method to identify the predominant tautomer.

A novel synthesis of 1-aryl-3-piperidone derivatives

A novel method to construct the 1-aryl-3-piperidone scaffold is described here. Starting from 3,5-dichloroaniline, a seven-step synthesis, without the use of protecting groups, generates the desired 3-piperidone ring in an overall yield of 30% through a key Morita-Baylis-Hillman reaction and ring-closing metathesis, providing easy access to diverse and useful heterocycles.

Substituted pyrazolones require N2 hydrogen bond donating ability to protect against cytotoxicity from protein aggregation of mutant superoxide dismutase 1

Amyotrophic lateral sclerosis (ALS) is a debilitating and fatal neurodegenerative disease. Although the cause remains unknown, misfolded protein aggregates are seen in neurons of sporadic ALS patients, and familial ALS mutations, including mutations in superoxide dismutase 1 (SOD1), produce proteins with an increased propensity to misfold and aggregate. A structure activity relationship of a lead scaffold exhibiting neuroprotective activity in a G93A-SOD1 mouse model for ALS has been further investigated in a model PC12 cellular assay. Synthesis of biotinylated probes at the N(1) nitrogen of the pyrazolone ring gave compounds (5d-e) that retained activity within 10-fold of the proton-bearing lead compound (5a) and were equipotent with a sterically less cumbersome N(1)-methyl substituted analogue (5b). However, when methyl substitution was introduced at N(1) and N(2) of the pyrazolone ring, the compound was inactive (5c). These data led us to investigate further the pharmacophoric nature of the pyrazolone unit. A range of N(1) substitutions were tolerated, leading to the identification of an N(1)-benzyl substituted pyrazolone (5m), equipotent with 5a. Substitution at N(2) or excision of N(2), however, removed all activity. Therefore, the hydrogen bond donating ability of the N(2)-H of the pyrazolone ring appears to be a critical part of the structure, which will influence further analogue synthesis.

Chiral cyclohexane 1,3-diones as inhibitors of mutant SOD1-dependent protein aggregation for the treatment of ALS

Cyclohexane 1,3-diones were identified as a class of molecules exhibiting a protective effect against mutant SOD1 induced toxicity in PC-12 cells, but an optimized analogue had little or no effect on life extension in the G93A SOD1 mouse model for amyotrophic lateral sclerosis (ALS). Additional testing showed that these compounds were inactive in neurons and further analogue synthesis was carried out to identify compounds with neuronal activity. Starting from two racemic derivatives that were active in cortical neurons, two potent analogues (1b and 2b) were resolved, which were protective against mutant SOD1 induced toxicity in PC-12 cells. Both compounds were found to be active in cortical neurons and presented good ADME profiles in vitro. On the basis of these results, an ALS mouse trial with 1b was carried out, which showed slightly greater life extension than the FDA-approved ALS drug riluzole, thereby validating cyclohexane 1,3-diones as a novel therapeutic class for the treatment of ALS.

Regioselective synthesis of heteroaryl triflones by LDA (lithium diisopropylamide)-mediated anionic thia-Fries rearrangement

Novel heteroaryl triflones including oxindole, pyrazolone, pyridine, and quinoline derivatives have been regioselectively synthesized by LDA-mediated thia-Fries rearrangement for the first time. These reactions are also the first examples of the application of anionic thia-Fries rearrangement in heteroaromatic compounds.

Direct amination of γ-halo-β-ketoesters with anilines

The direct amination of α-haloacetoacetates with anilines is described. Compared to existing methods, this simple protocol provides an attractive strategy to prepare diverse γ-anilino-β-ketoesters in one step. Good to excellent yields of the amination products were obtained under robust conditions, providing versatile and useful scaffolds.