Autophagy inhibition potentiates energy restriction-induced cell death in hepatocellular carcinoma cells.

Hepatocellular carcinoma (HCC) significantly contributes to cancer-related mortality due to the limited response of HCC to current anticancer therapies, thereby necessitating more effective treatment approaches. Energy restriction mimetic agents (ERMAs) have emerged as potential therapies in targeting the Warburg effect, a unique metabolic process in cancer cells. However, ERMAs exhibit limited efficacy when used as monotherapy. Additionally, ERMAs have been found to induce autophagy in cancer cells. The role of autophagy in cancer survival remains a subject of debate. Thus, it is crucial to ascertain whether ERMA-induced autophagy is a mechanism for cell survival or cell death in HCC. Our study aims to investigate the effect of autophagy inhibition on the survival of HCC cells treated with ERMAs while also examining the potential of combining an autophagy inhibitor such as spautin-1 with ERMAs to enhance HCC cell death. Our results suggest a cytoprotective role for ERMA-induced autophagy in HCC cells, as combining the autophagy inhibitor spautin-1 with ERMAs effectively suppressed ERMA-induced autophagy and synergistically enhanced their antitumor activity. The treatment combination promoted HCC death through apoptosis, cell cycle arrest, and inhibition of AKT and ERK activation, which are known to play a key role in cellular proliferation. Collectively, our findings highlight a potential strategy to combat HCC by combining energy restriction with autophagy inhibition.

Synthesis, biological evaluation, and stability studies of raloxifene mono- and bis-sulfamates as dual-targeting agents.

All three possible sulfamate derivatives of the selective estrogen receptor modulator Raloxifene (bis-sulfamate 7 and two mono-sulfamates 8-9) were synthesized and evaluated as inhibitors of the clinical drug target steroid sulfatase (STS), both in cell-free and in cell-based assays, and also as estrogen receptor (ER) modulators. Bis-sulfamate 7 was the most potent STS inhibitor with an IC50 of 12.2 nM in a whole JEG3 cell-based assay, with the two mono-sulfamates significantly weaker. The estrogen receptor-modulating activities of 7-9 showed generally lower affinities compared to Raloxifene HCl, diethylstilbestrol and other known ligands, with mono-sulfamate 8 being the best ligand (Ki of 1.5 nM) for ERα binding, although 7 had a Ki of 13 nM and both showed desirable antagonist activity. The antiproliferative activities of the sulfamate derivatives against the T-47D breast cancer cell line showed 7 as most potent (GI50 = 7.12 µM), comparable to that of Raloxifene. Compound 7 also showed good antiproliferative potency in the NCI-60 cell line panel with a GI50 of 1.34 µM against MDA-MB-231 breast cancer cells. Stability testing of 7-9 showed that bis-sulfamate 7 hydrolyzed by desulfamoylation at a surprisingly rapid rate, initially leading selectively to 8 and finally to Raloxifene 3 without formation of 9. The mechanisms of these hydrolysis reactions could be extensively rationalized. Conversion of Raloxifene (3) into its bis-sulfamate (7) thus produced a promising drug lead with nanomolar dual activity as an STS inhibitor and ERα antagonist, as a potential candidate for treatment of estrogen-dependent breast cancer.

Stereodivergent Desymmetrization of Phenols En Route to Modular Access to Densely Functionalized Quinazoline and Oxazine Scaffolds.

The de novo assembly of stereochemically and skeletally diverse scaffolds is a powerful tool for the discovery of novel chemotypes. Hence, the development of modular, step- and atom-economic synthetic methods to access stereochemically and skeletally diverse compound collection is particularly important. Herein, we show a metal-free, stereodivergent build/couple/pair strategy that allows access to a unique collection of benzo[5,6][1,4]oxazino[4,3-a]quinazoline, quinolino[1,2-a]quinazoline and benzo[b]benzo [4,5]imidazo[1,2-d][1,4]oxazine scaffolds with complete diastereocontrol and wide distribution of molecular architectures. This metal-free process proceeds via desymmetrization of phenol derivatives. The cascade unites Mannich with aza-Michael addition reactions, providing expeditious entries to diverse classes of molecular shapes in a single operation.

Divergent Protocol for the Synthesis of Isoquinolino[1,2-b]quinazolinone and Isoquinolino[2,1-a]quinazolinone Derivatives.

The development of robust and step-economic strategies to access structurally diverse drug-like compound collections remains a challenge. A distinct structural option that constitutes the core scaffold of many biologically significant molecules is the quinazolinone ring system. Several members of this family of privileged substructures have gained attention due to their diverse biological activities. In this context, the development of an efficient strategy for their access is needed. Herein, we report a divergent metal-free operation to access a diverse collection of C6-substituted pyrrolo[4',3',2':4,5]isoquinolino[1,2-b]quinazolin-8(6H)-one and pyrrolo[4',3',2':4,5]isoquinolino[2,1-a]quinazolin-12(6H)-one architectures. The described cascade unites Friedel-Crafts and aza-Michael addition reactions. This operationally simple protocol enables a rapid access to these scaffolds and is compatible with a wide scope of starting materials. In addition, the cascade features a promising approach for the design of unique compound libraries for drug design and discovery programs.

Blue Light-Driven [4+2]-Cycloaddition: Diastereoselective Synthesis of Chromeno[4,3-b]quinoline and Chromeno[4,3-b][1,8]naphthyridine Scaffolds.

A one-pot, metal-free, light-driven [4+2]-cycloaddition reaction is described by accessing a diverse collection of chromeno[4,3-b]quinoline and chromeno[4,3-b][1,8]naphthyridine scaffolds in a diastereoselective manner. This process delivered stereoisomers, which were challenging to produce by an inverse-demand Diels-Alder reaction. The tetracyclic products were provided in good yields, promoted by rose bengal and blue light in a single operation. The developed protocol proceeded efficiently without the need for expensive photosensitizers such as Ir or Ru complexes. The cascade is modular and step-economic, and the substrate scope is wide. Polycyclic architectures can be assembled from readily available aniline, aminoazine, indole, and salicylaldehyde derivatives.

Stereodivergent Complexity-to-Diversity Strategy en Route to the Synthesis of Nature-Inspired Skeleta.

The complexity-to-diversity (CtD) strategy has become one of the most powerful tools used to transform complex natural products into diverse skeleta. However, the reactions utilized in this process are often limited by their compatibility with existing functional groups, which in turn restricts access to the desired skeletal diversity. In the course of employing a CtD strategy en route to the synthesis of natural product-inspired compounds, our group has developed several stereodivergent strategies employing indoloquinolizine natural product analogues as starting materials. These transformations led to the rapid and diastereoselective synthesis of diverse classes of natural product-like architectures, including camptothecin-inspired analogues, azecane medium-sized ring systems, arborescidine-inspired systems, etc. This manifestation required a drastic modification of the synthetic design that ultimately led to modular and diastereoselective access to a diverse collection of various classes of biologically significant natural product analogues. The reported strategies provide a unique platform that will be broadly applicable to other late-stage natural product transformation approaches.

Design, synthesis, and biological evaluation of a new series of pyrazole derivatives: Discovery of potent and selective JNK3 kinase inhibitors.

The design, synthesis, and biological activities of a new series of pyrazole derivatives are reported. The target compounds 1a-1w were initially investigated against NCI-60 cancer cell lines. Compounds 1f, 1h, 1k, and 1v exerted the highest anti-proliferative activity over the studied panel of cancer cell lines. Compound 1f showed the most potent activity, and it is more potent than sorafenib in 29 cancer cell lines of different types and more potent than SP600125 against almost all the tested cancer cell lines. It also exerted sub-micromolar IC50 values (0.54-0.98 µM) against nine cell lines. Moreover, the 23 target compounds were tested against Hep3B and HepG2 hepatocellular carcinoma cell lines, of which compounds 1b, 1c, and 1h showed the strongest anti-proliferative activity. The most potent anticancer compounds (1b, 1c, 1f, and 1h) demonstrated a high selectivity towards cancer cells vis-à-vis normal cells. Compounds1f and 1h induced apoptosis and mild necrosis upon testing against RPMI-8226 leukemia cells. Kinase profiling of this series led to the discovery of two potent and selective JNK3 inhibitors, compounds 1c and 1f with an IC50 values of 99.0 and 97.4 nM, respectively. Both compounds showed a good inhibitory effect against JNK3 kinase in the whole-cell NanoBRET assay. This finding was further supported through molecular modeling studies with the JNK3 binding site. Moreover, compounds 1c and 1f demonstrated a very weak activity against CYP 2D6, CYP 3A4, and hERG ion channels.

Stereoselective Late-Stage Transformations of Indolo[2,3-a]quinolizines Skeleta to Nature-Inspired Scaffolds.

The indolo[2,3-a]quinolizines, canthines, and arborescidines natural products exhibit a wide range of bioactivities including anticancer, antiviral, antibacterial, and anti-inflammatory, among others. Therefore, the development of modular and efficient strategies to access the core scaffolds of these classes of natural products is a remarkable achievement. The Complexity-to-Diversity (CtD) strategy has become a powerful tool that transforms natural products into skeletal and stereochemical diversity. However, many of the reactions that could be utilized in this process are limited by the type of functional groups present in the starting material, which restrict transformations into a variety of products to achieve the desired diversity. In the course of employing a (CtD) strategy en route to the synthesis of nature-inspired compounds, unexpected stereoelectronic-driven rearrangement reactions have been discovered. These reactions provided a rapid access to indolo[2,3-a]quinolizines-, canthines-, and arborescidines-inspired alkaloids in a modular and diastereoselective manner. The disclosed strategies will be widely applicable to other late-stage natural product transformation programs and drug discovery initiatives.

Discovery of Novel Small-Molecule Inhibitors of SARS-CoV-2 Main Protease as Potential Leads for COVID-19 Treatment.

The main protease of SARS-CoV-2 virus, Mpro, is an essential element for viral replication, and inhibitors targeting Mpro are currently being investigated in many drug development programs as a possible treatment for COVID-19. An in vitro pilot screen of a highly focused collection of compounds was initiated to identify new lead scaffolds for Mpro. These efforts identified a number of hits. The most effective of these was compound SIMR-2418 having an inhibitory IC50 value of 20.7 µM. Molecular modeling studies were performed to understand the binding characteristics of the identified compounds. The presence of a cyclohexenone warhead group facilitated covalent binding with the Cys145 residue of Mpro. Our results highlight the challenges of targeting Mpro protease and pave the way toward the discovery of potent lead molecules.

Discovery of novel class of histone deacetylase inhibitors as potential anticancer agents.

Selective inhibition of histone deacetylases (HDACs) is an important strategy in the field of anticancer drug discovery. However, lack of inhibitors that possess high selectivity toward certain HDACs isozymes is associated with adverse side effects that limits their clinical applications. We have initiated a collaborative initiatives between multi-institutions aimed at the discovery of novel and selective HDACs inhibitors. To this end, a phenotypic screening of an in-house pilot library of about 70 small molecules against various HDAC isozymes led to the discovery of five compounds that displayed varying degrees of HDAC isozyme selectivity. The anticancer activities of these molecules were validated using various biological assays including transcriptomic studies. Compounds 15, 14, and 19 possessed selective inhibitory activity against HDAC5, while 28 displayed selective inhibition of HDAC1 and HDAC2. Compound 22 was found to be a selective inhibitor for HDAC3 and HDAC9. Importantly, we discovered a none-hydroxamate based HDAC inhibitor, compound 28, representing a distinct chemical probe of HDAC inhibitors. It contains a trifluoromethyloxadiazolyl moiety (TFMO) as a non-chelating metal-binding group. The new compounds showed potent anti-proliferative activity when tested against MCF7 breast cancer cell line, as well as increased acetylation of histones and induce cells apoptosis. The new compounds apoptotic effects were validated through the upregulation of proapoptotic proteins caspases3 and 7 and downregulation of the antiapoptotic biomarkers C-MYC, BCL2, BCL3 and NFĸB genes. Furthermore, the new compounds arrested cell cycle at different phases, which was confirmed through downregulation of the CDK1, 2, 4, 6, E2F1 and RB1 proteins. Taken together, our findings provide the foundation for the development of new chemical probes as potential lead drug candidates for the treatment of cancer.

Metabolic conversion of ß-pinene to ß-ionone in rats.

Exposure to or ingestion of turpentine can alter the scent of urine, conferring it a flowery, violet-like scent. Turpentine's effect on urine was initially noticed after its use either as medicine or as a preservative in winemaking. Regardless of the source of exposure, the phenomenon requires metabolic conversion of turpentine component(s) to ionone, the molecule mainly responsible for the scent of violets.The purpose of this study was to identify the presence of ionone in the urine of rats that received ß-pinene, and thus to demonstrate that the postulated conversion occurs.We treated rats intraperitoneally with normal saline (negative control), ß-ionone (positive control), low-dose ß-pinene (1/3 of LD50), and high-dose ß-pinene (1/2 of LD50). Urine samples were collected up to 72 h after administration of the compounds, followed by gas chromatography/mass spectrometry identification of the presence of ionone.ß-Ionone was found in the urine of rats exposed to both low and high doses of ß-pinene. In contrast, α-ionone appears unlikely to have been formed in rats exposed to either low or high doses of ß-pinene. ß-pinene was converted to ß-ionone, followed by partial excretion in the urine of rats. ß-Ionone is a minor metabolite of ß-pinene.

BACE1 inhibitors: Current status and future directions in treating Alzheimer's disease.

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative brain disorder with no current cure. One of the important therapeutic approaches of AD is the inhibition of ß-site APP cleaving enzyme-1 (BACE1), which is involved in the rate-limiting step of the cleavage process of the amyloid precursor protein (APP) leading to the generation of the neurotoxic amyloid ß (Aß) protein after the γ-secretase completes its function. The produced insoluble Aß aggregates lead to plaques deposition and neurodegeneration. BACE1 is, therefore, one of the attractive targets for the treatment of AD. This approach led to the development of potent BACE1 inhibitors, many of which were advanced to late stages in clinical trials. Nonetheless, the high failure rate of lead drug candidates targeting BACE1 brought to the forefront the need for finding new targets to uncover the mystery behind AD. In this review, we aim to discuss the most promising classes of BACE1 inhibitors with a description and analysis of their pharmacodynamic and pharmacokinetic parameters, with more focus on the lead drug candidates that reached late stages of clinical trials, such as MK8931, AZD-3293, JNJ-54861911, E2609, and CNP520. In addition, the manuscript discusses the safety concerns and insignificant physiological effects, which were highlighted for the most successful BACE1 inhibitors. Furthermore, the review demonstrates with increasing evidence that despite tremendous efforts and promising results conceived with BACE1 inhibitors, the latest studies suggest that their clinical use for treating Alzheimer's disease should be reconsidered. Finally, the review sheds light on alternative therapeutic options for targeting AD.

Divergent Strategy for Diastereocontrolled Synthesis of Small- and Medium-Ring Architectures.

Nitrogen and oxygen medium rings, in particular nine-membered rings, epitomize a unique area of chemical space that occurs in many natural products and biologically appealing compounds. The scarcity of 8- to 12-membered rings among clinically approved drugs is indicative of the difficulties associated with their synthesis, principally owing to the unfavorable entropy and transannular strain. We report here a scandium triflate-catalyzed reaction that allows for a modular access to a diverse collection of nine-membered ring heterocycles in a one-pot cascade and with complete diastereocontrol. This cascade features an intramolecular addition of an acyl group-derived enol to a α,ß-unsaturated carbonyl moiety, leading to N- and O-derived medium-ring systems. Computational studies using the density functional theory support the proposed mechanism. Additionally, a one-pot cascade leading to hexacyclic chromeno[3',4':2,3]indolizino[8,7-b]indole architectures, with six fused rings and four contiguous chiral centers, is reported. This novel cascade features many concerted events, including the formation of two azomethine ylides, [3 + 2]-cycloaddition, 1,3-sigmatropic rearrangement, Michael addition, and Pictet-Spengler reaction among others. Phenotypic screening of the resulting oxazonine collection identified chemical probes that regulate mitochondrial membrane potential, adenosine 5'-triphosphate contents, and reactive oxygen species levels in hepatoma cells (Hepa1-6), a promising approach for targeting cancer and metabolic disorders.

Stereocontrolled transformations of cyclohexadienone derivatives to access stereochemically rich and natural product-inspired architectures.

The last two decades or so have witnessed an upsurge in defining the art of designing complex natural products and nature-inspired molecules. Throughout these decades, fundamental insights into stereocontrolled, step-economic and atom-economical synthesis principles were achieved by the numerous synthetic accomplishments particularly in diversity-oriented synthesis (DOS). This has empowered the visualization of the third dimension in synthetic design and thus has resulted in a dramatic increase with today's diversity-oriented synthesis (DOS) at the forefront enabling access to diverse scaffolds with a high degree of stereochemical and skeletal complexity. To this end, a starting material-based approach is one of the powerful tools utilized in DOS that allows rapid access to molecular architectures with a high sp3 content. Skeletal and stereochemical diversity is often paramount for the selective modulation of the biological function of a complementary protein in the biological space. In this context, stereocontrolled transformation of cyclohexadienone scaffolds has positioned itself as a powerful platform for the rapid generation of stereochemically enriched and natural product-inspired compound collections. In this review, we cover multidirectional synthetic strategies that utilized cyclohexadienone derivatives as pluripotent building blocks en route for the construction of novel chemical space.

Domino Transformations of Ene/Yne Tethered Salicylaldehyde Derivatives: Pluripotent Platforms for the Construction of High sp3 Content and Privileged Architectures.

Diversity-oriented synthesis (DOS) has become a powerful synthetic tool that facilitates the construction of nature-inspired and privileged chemical space, particularly for sp3 -rich non-flat scaffolds, which are needed for phenotypic screening campaigns. These diverse compound collections led to the discovery of novel chemotypes that can modulate the protein function in underrepresented biological space. In this context, starting material-driven DOS is one of the most important tools used to build diverse compound libraries with rich stereochemical and scaffold diversity. To this end, ene/yne tethered salicylaldehyde derivatives have emerged as a pluripotent chemical platform, the products of which led to the construction of a privileged chemical space with significant biological activities. In this review, various domino transformations employing o-alkene/alkyne tethered aryl aldehyde/ketone platforms are described and discussed, with emphasis on the period from 2011 to date.

Sequencing [4 + 1]-Cycloaddition and Aza-Michael Addition Reactions: A Diastereoselective Cascade for the Rapid Access of Pyrido[2',1':2,3]/Thiazolo[2',3':2,3]imidazo[1,5-a]quinolone Scaffolds as Potential Antibacterial and Anticancer Motifs.

The design and synthesis of a quality compound library containing a small number of skeletally diverse scaffolds, whose members rapidly deliver new chemical probes active against multiple phenotypes, is paramount in drug discovery. In this context, an efficient one-pot strategy for the synthesis of a mini library of sp3-enriched hexahydropyrido[2',1':2,3]imidazo[1,5-a]quinolinium and hexahydrothiazolo[2',3':2,3]imidazo[1,5-a]quinolinium architectures, is described. This new one-pot method features a combination of Sc(OTf)3-catalyzed [4 + 1]-cycloaddition with aza-Michael addition reactions. The cascade results in a rapid and diastereoselective formation of these scaffolds via desymmetrization of the oxidative dearomatization products of phenols. Phenotypic screening of the mini library against multiple drug-resistant bacteria and a panel of cancer cell lines identified potential antibacterial and anticancer lead drug candidates. Further investigation of the anticancer leads, indicated by their activity as tubulin-polymerization inhibitors, represents a promising approach for cancer therapy.

One-Pot Synthesis of Diverse Collections of Benzoxazepine and Indolopyrazine Fused to Heterocyclic Systems.

The development of efficient and modular synthetic methods for the synthesis of diverse collection of privileged substructures needed for a drug design and discovery campaign is highly desirable. Benzoxazepine and indolopyrazine ring systems form the core structures of distinct members of biologically significant molecules. Several members of these families have gained attention due to their broad biological activities, which depend on the type of ring-fusion and peripheral substitution patterns. Despite the potential applications of these privileged substructures in drug discovery, efficient, atom-economic, and modular strategies for their access are underdeveloped. Herein, a one-step build/couple/pair strategy that uniquely allows access to diversely functionalized benzoxazepine and indolopyrazine scaffolds is described. The methodology features a one-pot combination of condensation, Mannich, oxidation, and aza-Michael addition reactions, employing a variety of functionalized anilines and aldehydes suitably poised with Micheal acceptor. Scandium triflate (Sc(OTf)3) in acetonitrile (ACN) was found to promote the construction of benzoxazepines scaffolds, while sodium metabisulfite (Na2S2O5) in aqueous EtOH rapidly enhanced the cascade reaction that led to diverse collections of indolopyrazine frameworks. These protocols represent modular, efficient, and atom-economic access of constrained benzoxazepine and indolopyrazine systems with more than 10 points of diversity and large substrate tolerance.

Modular Bi-Directional One-Pot Strategies for the Diastereoselective Synthesis of Structurally Diverse Collections of Constrained ß-Carboline-Benzoxazepines.

The development of robust and efficient strategies to access structurally diverse drug-like compound collections remains an important challenge for small molecule probe development and drug discovery. Following a build/couple/pair strategy we have established bidirectional approach to unprecedented benzoxazepines by employing a Pictet-Spengler/aza-Michael addition cascade and Schiff base/aza-Michael addition/reduction protocols, respectively. The corresponding ß-carboline-fused benzoxazepines and peripherally substituted benzoxazepines are isolated in high diastereoselectivity, good to excellent yields and have, to the best of our knowledge, never been reported.

Intramolecular Diaza-Diels-Alder Protocol: A New Diastereoselective and Modular One-Step Synthesis of Constrained Polycyclic Frameworks.

Phenotype-based screening of diverse compound collections generated by privileged substructure-based diversity-oriented synthesis (pDOS) is considered one of the prominent approaches in the discovery of novel drug leads. However, one key challenge that remains is the development of efficient and modular synthetic routes toward the facile access of privileged small-molecule libraries with skeletal and stereochemical complexity and drug-like properties. In this regard, a novel and diverse one-pot procedure for the diastereoselective synthesis of privileged polycyclic benzopyrans and benzoxepines is described herein. These unexplored chemotypes were accessed by utilizing an acid-mediated diaza-Diels-Alder reaction of 2-allyloxy- and/or homoallyloxy benzaldehyde with 2-aminoazine building blocks. Profiling of representative analogues against blood-stage Plasmodium falciparum parasites identified three lead candidates with low micromolar antimalarial activity.

Flexible, polymer-supported synthesis of sphingosine derivatives provides ceramides with enhanced biological activity.

A polymer-supported route for the synthesis of sphingosine derivatives is presented based on the C-acylation of polymeric phosphoranylidene acetates with an Fmoc-protected amino acid. The approach enables the flexible variation of the sphingosine tail through a deprotection-decarboxylation sequence followed by E-selective Wittig olefination cleavage. d-Erythro-sphingosine analogs have been synthesized by diastereoselective reduction of the keto group employing LiAlH(O-tBu)3 as reducing agent. The effect of ceramides and keto-ceramides on the proliferation of three cancer cell lines HEP G-2, PC-12 and HL-60 was investigated and a ceramide containing an aromatic sphingosine tail was identified as being most active.