Oxindole: A chemical prism carrying plethora of therapeutic benefits

The protective role of two oxindole derivatives is mediated by modulating NLRP3/caspase-1 and PI3K/AKT pathways in a preclinical animal model of hepatic ischemia reperfusion injury

Aim Hepatic ischemia reperfusion injury (HIRI) is a leading cause of mortality post liver transplantation, hypovolemic shock and trauma. In this study, we tested, on molecular bases, the possible protective role of two different derivatives of 2-oxindole in a preclinical model of HIRI in rats.

MAIN METHODS

HIRI was operated in male Wistar albino rats and prophylactic treatment with oxindole-curcumin (Coxi) or oxindole-vanillin (Voxi) was carried out before the operation. The biochemical and histopathological investigations, in addition to the mechanistic characterizations of the effect of the tested drugs were performed.

KEY FINDINGS

HIRI was assured with elevated liver enzymes and marked changes in histopathological features, inflammatory response and oxidative stress. Pretreatment with Coxi and Voxi improved the hepatic histopathological alterations, reduced the elevated serum liver enzymes level and hepatic Malondialdehyde (MDA) content, increased the hepatic Superoxide Dismutase (SOD) activity and reduced Glutathione (GSH) content, downregulated the expression of TNF-α, IL-6, Nod-Like Receptor p3 (NLRP3), Cleaved caspase1, Cleaved caspase 3 proteins, alongside the expression level of IL-1β, ICAM-1, VCAM-1 and BAX genes, attenuated NF-кB p-P65 Ser536 and Myeloperoxidase (MPO)-positive neutrophils, and activated the PI3K/AKT pathway.

SIGNIFICANCE

Coxi and Voxi have promising hepatoprotective activity against HIRI in rats through ameliorating the biochemical and histopathological alterations, attenuating inflammatory and oxidative stress status by modulating the inflammatory TNF-α/ICAM-1, the pyroptosis NLRP3/Caspase-1, and the antioxidant PI3K/AKT pathways.

Organocatalyzed Asymmetric Michael Addition of 3-Fluorooxindole to Vinylidene Bisphosphonates

Both the 3-fluorooxindole and germinal bisphosphonate structural motifs are prevalent in bioactive molecules because of their associated biological activities. We describe an approach to accessing 3,3-disubstituted 3-fluorooxindoles bearing a geminal bisphosphate fragment through a highly enantioselective Michael addition reaction between 3-fluorooxindoles and vinylidene bisphosphonates. These reactions are catalyzed by a commercially available cinchona alkaloid catalyst, have a broad substrate scope concerning 3-fluorooxindoles, and provide the corresponding addition products in a yield of up to 95% with an enantiomeric excess of up to 95%. A reasonable reaction pathway to explain the observed stereochemistry is also proposed.

Design, synthesis, and biological evaluation of 2-(2-oxoindolin-3-ylidene)hydrazinecarbothioamides as a potential EGR-1 inhibitor for targeted therapy of atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease characterized by intense itching and frequent skin barrier dysfunctions. EGR-1 is a transcription factor that aggravates the pathogenesis of atopic dermatitis by promoting the production of various inflammatory cytokines. Three 2-(2-oxoindolin-3-ylidene)hydrazinecarbothioamides (IT21, IT23, and IT25) were identified as novel inhibitors of EGR-1 DNA-binding activity. In silico docking experiments were performed to elucidate the binding conditions of the EGR-1 zinc-finger (ZnF) DNA-binding domain. Electrophoretic mobility shift assays confirmed the targeted binding effect on the EGR-1 ZnF DNA-binding domain, leading to dose-dependent dissociation of the EGR-1-DNA complex. At the functional cellular level, IT21, IT23, and IT25 effectively reduced mRNA expression of TNFα-induced EGR-1-regulated inflammatory genes, particularly in HaCaT keratinocytes inflamed by TNFα. In the in vivo efficacy study, IT21, IT23, and IT25 demonstrated the potential to alleviate atopic dermatitis-like skin lesions in the ear skin of BALB/c mice. These findings suggest that targeting the EGR-1 ZnF DNA-binding domain with 2-(2-oxoindolin-3-ylidene)hydrazinecarbothioamide derivatives (IT21, IT23, and IT25) could serve as lead compounds for the development of potential therapeutic agents against inflammatory skin disorders, including atopic dermatitis.

Discovery and optimization of narrow spectrum inhibitors of Tousled like kinase 2 (TLK2) using quantitative structure activity relationships

The oxindole scaffold has been the center of several kinase drug discovery programs, some of which have led to approved medicines. A series of two oxindole matched pairs from the literature were identified where TLK2 was potently inhibited as an off-target kinase. The oxindole has long been considered a promiscuous kinase inhibitor template, but across these four specific literature oxindoles TLK2 activity was consistent, while the kinome profile was radically different ranging from narrow to broad spectrum kinome coverage. We synthesized a large series of analogues, utilizing quantitative structure-activity relationship (QSAR) analysis, water mapping of the kinase ATP binding sites, kinome profiling, and small-molecule x-ray structural analysis to optimize TLK2 inhibition and kinome selectivity. This resulted in the identification of several narrow spectrum, sub-family selective, chemical tool compounds including 128 (UNC-CA2-103) that could enable elucidation of TLK2 biology.

Physicochemical properties, pharmacokinetic studies, DFT approach, and antioxidant activity of nitro and chloro indolinone derivatives

The process of developing of new drugs is greatly hampered by their inadequate physicochemical, pharmacokinetic, and intrinsic characteristics. In this regard, the selected chloro indolinone, (Z)-6-chloro-3-(2-chlorobenzylidene)indolin-2-one (C1), and nitro indolinone, (Z)-6-chloro-3-(2-nitrobenzylidene)indolin-2-one (C2), were subjected to SwissADME and density function theory (DFT) analysis. For compounds C1 and C2, the BOILED-Egg pharmacokinetic model predicted intestinal absorption, blood-brain barrier (BBB) penetration, and p-glycoprotein interaction. According to the physicochemical analysis, C1 has exceptional drug-like characteristics suitable for oral absorption. Despite only being substrates for some of the major CYP 450 isoforms, compounds C1 and C2 were anticipated to have strong plasma protein binding and efficient distribution and block these isoforms. The DFT study using the B3LYP/6-311G(d,p) approach with implicit water effects was performed to assess the structural features, electronic properties, and global reactivity parameters (GRP) of C1 and C2. The DFT results provided further support for other studies, implying that C2 is more water-soluble than C1 and that both compounds can form hydrogen bonds and (weak) dispersion interactions with other molecules, such as solvents and biomolecules. Furthermore, the GRP study suggested that C1 should be more stable and less reactive than C2. A concentration-dependent 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity was shown by both C1 and C2. In brief, this finding has provided a strong foundation to explore further the therapeutic potential of these molecules against a variety of human disorders.

Pd-Catalyzed Enantioselective Creation of All-Carbon Quaternary Center with 2,3-Allenylic Carbonates

Enantioselective construction of all-carbon quaternary centers has been achieved via the palladium-catalyzed highly enantioselective allenylation of oxindoles with 2,3-allenylic carbonates to afford a variety of optically active allene products, which contain oxindole units with different functional groups, in high ee. The corresponding synthetic applications have also been demonstrated.

Regiodivergent Ring-Expansion of Oxindoles to Quinolinones

The development of divergent methods to expedite structure-activity relationship studies is crucial to streamline discovery processes. We developed a rare example of regiodivergent ring expansion to access two regioisomers from a common starting material. To enable this regiodivergence, we identified two distinct reaction conditions for transforming oxindoles into quinolinone isomers. The presented methods proved to be compatible with a variety of functional groups, which enabled the late-stage diversification of bioactive oxindoles as well as facilitated the synthesis of quinolinone drugs and their derivatives.

Novel 5-Substituted Oxindole Derivatives as Bruton's Tyrosine Kinase Inhibitors: Design, Synthesis, Docking, Molecular Dynamics Simulation, and Biological Evaluation

Bruton's tyrosine kinase (BTK) is a non-RTK cytoplasmic kinase predominantly expressed by hemopoietic lineages, particularly B-cells. A new oxindole-based focused library was designed to identify potent compounds targeting the BTK protein as anticancer agents. This study used rational approaches like structure-based pharmacophore modeling, docking, and ADME properties to select compounds. Molecular dynamics simulations carried out at 20 ns supported the stability of compound 9g within the binding pocket. All the compounds were synthesized and subjected to biological screening on two BTK-expressing cancer cell lines, RAMOS and K562; six non-BTK cancer cell lines, A549, HCT116 (parental and p53-/-), U2OS, JURKAT, and CCRF-CEM; and two non-malignant fibroblast lines, BJ and MRC-5. This study resulted in the identification of four new compounds, 9b, 9f, 9g, and 9h, possessing free binding energies of -10.8, -11.1, -11.3, and -10.8 kcal/mol, respectively, and displaying selective cytotoxicity against BTK-high RAMOS cells. Further analysis demonstrated the antiproliferative activity of 9h in RAMOS cells through selective inhibition of pBTK (Tyr223) without affecting Lyn and Syk, upstream proteins in the BCR signaling pathway. In conclusion, we identified a promising oxindole derivative (9h) that shows specificity in modulating BTK signaling pathways.

Late-Stage Chemo- and Enantioselective Oxidation of Indoles to C3-Monosubstituted Oxindoles

Catalytic asymmetric preparation of chiral 3-monosubstituted oxindoles represents a significant challenge in synthetic chemistry due to the ease of racemization of the tertiary stereocenter through enolization. Here, we describe a general titanium-catalyzed chemo- and enantioselective indole oxidation to produce a diverse set of chiral 3-monosubstituted oxindoles with up to 96% yield, 99% ee, and with a substrate/catalyst ratio of 10,000 by using the combination of a simple titanium(salan) catalyst with green and atom-economic terminal oxidant H2O2. The mild approach tolerates a broad range of functional groups, enabling late-stage asymmetric diversification of a series of commercial drugs and natural products together with late-stage asymmetric construction of a wide set of enzyme antagonists, all of which are difficult to achieve through existing methods.

One-Pot, Tandem Reductive Amination/Alkylation-Cycloamidation for Lactam Synthesis from Keto or Amino Acids

Monotrifluoroacetoxyborane-amines, prepared by treating borane-amines with trifluoroacetic acid, have been shown to be efficient reagents for a one-pot, tandem reductive amination/alkylation-cycloamidation of keto or amino acids to achieve the synthesis of 5-aryl or 5-methyl pyrrolidin-2-ones and 6-aryl or 6-methyl piperidin-2-ones.

Bifunctional Thiourea-Catalyzed Enantioselective Aza-Friedel-Crafts Reaction of 3-Aminobenzofurans with Isatin-Derived Ketimines

A quinine-derived thiourea-promoted enantioselective aza-Friedel-Crafts reaction of 3-aminobenzofurans with isatin-derived ketimines is developed, providing a variety of 3-benzofuran-3-amino-2-oxindoles bearing a quaternary stereocenter with good to excellent yields (72-95%) and moderate to excellent enantioselectivities (48-97%). The synthetic potential of this concise and efficient protocol is revealed by gram-scale preparation and further transformation of the adduct to an optically pure spirocyclic oxindole.

Oxindole and Benzoxazinone Alkaloids from the Seeds of Persea americana (Avocado) and Their SIRT1 Stimulatory Activity

Persea americana Mill. (Lauraceae), commonly known as avocado, is a well-known food because of its nutrition and health benefits. The seeds of avocado are major byproducts, and thus their phytochemicals and bioactivities have been of interest for study. The chemical components of avocado seeds were investigated by using UPLC-qTOF-MS/MS-based molecular networking, resulting in the isolation of seven new oxindole alkaloids (1-7) and two new benzoxazinone alkaloids (8 and 9). The chemical structures of the isolated compounds were identified by the analysis of NMR data in combination with computational approaches, including NMR and ECD calculations. Bioactivities of the isolated compounds toward silent information regulation 2 homologue-1 (SIRT1) in HEK293 cells were assessed. The results showed that compound 1 had the most potent effect on SIRT1 activation with an elevated NAD+/NADH ratio with potential for further investigation as an anti-aging agent.

Rh(III)-Catalyzed [3 + 2] Annulation/Pinacol Rearrangement Reaction of Enaminones with Iodonium Ylides: Direct Synthesis of 2-Spirocyclo-pyrrol-3-ones

A novel Rh(III)-catalyzed cascade alkenyl C-H activation/[3 + 2] annulation/pinacol rearrangement reaction of enaminones with iodonium ylides has been developed. This methodology provides a new and straightforward synthetic strategy to afford highly functionalized 2-spirocyclo-pyrrol-3-ones in satisfactory yield from readily available starting materials under mild conditions. Moreover, gram-scale reactions and further derivatization experiments are implemented to demonstrate the potential utility of this developed approach.

Ortho-Selective amination of arene carboxylic acids via rearrangement of acyl O-hydroxylamines

Direct amination of arene C-H bonds is an attractive disconnection to form aniline-derived building blocks. This transformation presents significant practical challenges; classical methods for ortho-selective amination require strongly acidic or forcing conditions, while contemporary catalytic processes often require bespoke directing groups and/or precious metal catalysis. We report a mild and procedurally straightforward ortho-selective amination of arene carboxylic acids, arising from a facile rearrangement of acyl O-hydroxylamines without requiring precious metal catalysts. A broad scope of benzoic acid substrates are compatible and the reaction can be applied to longer chain arene carboxylic acids. Mechanistic studies probe the specific requirement for trifluoroacetic acid in generating the active aminating agent, and suggest that two separate mechanisms may be operating in parallel in the presence of an iron catalyst: (i) an iron-nitrenoid intermediate and (ii) a radical chain pathway. Regardless of which mechanism is followed, high ortho selectivity is obtained, proposed to arise from the directivity (first) or attractive interactions (second) arising with the carboxylic acid motif.

Synthetic strategies for the construction of C3-fluorinated oxindoles

C3-fluorinated oxindoles are important scaffolds known to demonstrate various biological properties. As bio-isosteres of oxindoles, these compounds have shown tremendous potential in drug research discovery programs. Besides, they also serve as starting materials for synthesizing other fluorine-containing new architectures, thus launching research for developing new methods for their synthesis. Consequently, various approaches have been developed over the years to synthesize C3-fluorinated oxindoles. This review highlights the strategies developed to date to access C3-difluoro and monofluorooxindoles via intermolecular and intramolecular approaches. The key findings of the strategies developed are discussed along with the prevailing mechanism.

Palladium-catalyzed Heck/aminocarbonylation of alkene-tethered carbamoyl chlorides with nitro compounds for the synthesis of carbamoyl-substituted oxindoles

A straightforward and efficient approach for the synthesis of carbamoyl-substituted oxindoles has been developed via a palladium-catalyzed Heck cyclization and reductive aminocarbonylation reaction of alkene-tethered carbamoyl chlorides with nitro compounds. The reaction showed good compatibility toward versatile functional groups, and both nitroarenes and nitroalkanes were well tolerated. Using Mo(CO)₆ as a solid CO source, without external reductants, a broad range of carbamoyl-substituted oxindoles were obtained in moderate to high yields.

Peptide-based metalloporphyrin catalysts: unveiling the role of the metal ion in indole oxidation

Over the last decades, much effort has been devoted to the construction of protein and peptide-based metalloporphyrin catalysts capable of promoting difficult transformations with high selectivity. In this context, mechanistic studies are fundamental to elucidate all the factors that contribute to catalytic performances and product selectivity. In our previous work, we selected the synthetic peptide-porphyrin conjugate MnMC6*a as a proficient catalyst for indole oxidation, promoting the formation of a 3-oxindole derivative with unprecedented selectivity. In this work, we have evaluated the role of the metal ion in affecting reaction outcome, by replacing manganese with iron in the MC6*a scaffold. Even though product selectivity is not altered upon metal substitution, FeMC6*a shows a lower substrate conversion and prolonged reaction times with respect to its manganese analogue. Experimental and theoretical studies have enabled us to delineate the reaction free energy profiles for both catalysts, indicating different thermodynamic limiting steps, depending on the nature of the metal ion.

Chemospecific C3- and C2-Olefinations of Isatins by TfOH-Promoted Tandem Aldol-Grob and Semiacetalization-Grob Fragmentations

A novel method for TfOH-promoted chemospecific C3- and C2-olefinations of isatins is developed, which offers the first examples of Grob fragmentation using isatins and amides as substrates.

Design, Synthesis, and Evaluation of the COX-2 Inhibitory Activities of New 1,3-Dihydro-2H-indolin-2-one Derivatives

Thirty-three 1,3-dihydro-2H-indolin-2-one derivatives bearing α, β-unsaturated ketones were designed and synthesized via the Knoevenagel condensation reaction. The cytotoxicity, in vitro anti-inflammatory ability, and in vitro COX-2 inhibitory activity of all the compounds were evaluated. Compounds 4a, 4e, 4i-4j, and 9d exhibited weak cytotoxicity and different degrees of inhibition against NO production in LPS-stimulated RAW 264.7 cells. The IC₅₀ values of compounds 4a, 4i, and 4j were 17.81 ± 1.86 μM, 20.41 ± 1.61 μM, and 16.31 ± 0.35 μM, respectively. Compounds 4e and 9d showed better anti-inflammatory activity with IC₅₀ values of 13.51 ± 0.48 μM and 10.03 ± 0.27 μM, respectively, which were lower than those of the positive control ammonium pyrrolidinedithiocarbamate (PDTC). Compounds 4e, 9h, and 9i showed good COX-2 inhibitory activities with IC₅₀ values of 2.35 ± 0.04 µM, 2.422 ± 0.10 µM and 3.34 ± 0.05 µM, respectively. Moreover, the possible mechanism by which COX-2 recognized 4e, 9h, and 9i was predicted by molecular docking. The results of this research suggested that compounds 4e, 9h, and 9i might be new anti-inflammatory lead compounds for further optimization and evaluation.

An Elusive Target: Inhibitors of JC Polyomavirus Infection and Their Development as Therapeutics for the Treatment of Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease caused by infection with JC Polyomavirus (JCPyV). Despite the identification of the disease and isolation of the causative pathogen over fifty years ago, no antiviral treatments or prophylactic vaccines exist. Disease onset is usually associated with immunosuppression, and current treatment guidelines are limited to restoring immune function. This review summarizes the drugs and small molecules that have been shown to inhibit JCPyV infection and spread. Paying attention to historical developments in the field, we discuss key steps of the virus lifecycle and antivirals known to inhibit each event. We review current obstacles in PML drug discovery, including the difficulties associated with compound penetrance into the central nervous system. We also summarize recent findings in our laboratory regarding the potent anti-JCPyV activity of a novel compound that antagonizes the virus-induced signaling events necessary to establish a productive infection. Understanding the current panel of antiviral compounds will help center the field for future drug discovery efforts.

(E)-5-(4-Meth-oxy-phen-yl)-N'-(2-oxoindolin-3-yl-idene)-1-phenyl-1H-pyrazole-3-carbohydrazide

The asymmetric unit of the title compound, C₂₅H₁₉N₅O₃, is composed of two independent mol-ecules with slightly different conformations. The extended structure features N-H⋯O hydrogen bonds as well as π-π inter-actions.

Antiferroptotic Activities of Oxindole GIF-0726-r Derivatives: Involvement of Ferrous Iron Coordination and Free-Radical Scavenging Capacities

Ferroptosis and oxytosis are iron- and oxidative stress-dependent cell death pathways strongly implicated in neurodegenerative diseases, cancers, and metabolic disorders. Therefore, specific inhibitors may have broad clinical applications. We previously reported that 3-[4-(dimethylamino)benzyl]-2-oxindole (GIF-0726-r) and derivatives protected the mouse hippocampal cell line HT22 against oxytosis/ferroptosis by suppressing reactive oxygen species (ROS) accumulation. In this study, we evaluated the biological activities of GIF-0726-r derivatives with modifications at the oxindole skeleton and other positions. The addition of a methyl, nitro, or bromo group to C-5 of the oxindole skeleton enhanced antiferroptotic efficacy on HT22 cells during membrane cystine-glutamate antiporter inhibition and ensued intracellular glutathione depletion. In contrast, the substitution of the dimethylamino group on the side chain phenyl ring with a methyl, nitro, or amine group dramatically suppressed antiferroptotic activity regardless of other modifications. Compounds with antiferroptotic activity also directly scavenged ROS and decreased free ferrous ions in both HT22 cells and cell-free reactions while those compounds without antiferroptotic activity had little effect on either ROS or ferrous-ion concentration. Unlike oxindole compounds, which we have previously reported, the antiferroptotic compounds had little effect on the nuclear factor erythroid-2-related factor 2-antioxidant response element pathway. Oxindole GIF-0726-r derivatives with a 4-(dimethylamino)benzyl moiety at C-3 and some types of bulky group at C-5 (whether electron-donating or electron-withdrawing) can suppress ferroptosis, warranting safety and efficacy evaluations in animal models of disease.

Palladium-Catalyzed Chemoselective Oxygenation of C(sp2)-H and C(sp3)-H Bonds in Isatins

The palladium-catalyzed chemoselective C(sp²)-H and C(sp³)-H bond oxygenation of substituted isatin derivatives is reported. This mild protocol exhibits the C5 C(sp²)-H oxygenation of isatins through electrophilic intermolecular C-H palladation in concentrated solutions using PhI(OAc)₂ or Selectfluor as an oxidant, whereas it exhibits-N-CH₃ C(sp³)-H oxygenation in dilute solutions via carbonyl-assisted intramolecular palladation in the presence of K₂S₂O₈. This oxygenation reaction provides a direct and unified approach for synthesizing diverse oxygenated isatins with sensitive functionalities, including biorelevant compounds.

Multicomponent synthesis of chromophores – The one-pot approach to functional π-systems

Multicomponent reactions, conducted in a domino, sequential or consecutive fashion, have not only considerably enhanced synthetic efficiency as one-pot methodology, but they have also become an enabling tool for interdisciplinary research. The highly diversity-oriented nature of the synthetic concept allows accessing huge structural and functional space. Already some decades ago this has been recognized for life sciences, in particular, lead finding and exploration in pharma and agricultural chemistry. The quest for novel functional materials has also opened the field for diversity-oriented syntheses of functional π-systems, i.e. dyes for photonic and electronic applications based on their electronic properties. This review summarizes recent developments in MCR syntheses of functional chromophores highlighting syntheses following either the framework forming scaffold approach by establishing connectivity between chromophores or the chromogenic chromophore approach by de novo formation of chromophore of interest. Both approaches warrant rapid access to molecular functional π-systems, i.e. chromophores, fluorophores, and electrophores for various applications.

A Bench-stable 8-Aminoquinoline Derived Phosphine-free Manganese (I)-Catalyst for Environmentally Benign C(α)-Alkylation of Oxindoles with Secondary and Primary Alcohols

Herein, we report a new air-stable phosphine-free 8-AQ (8-aminoquinoline) based Mn(I) carbonyl complex as the catalyst for the C(α)-alkylation of oxindoles with alcohols. The Mn complex [(8-AQ)Mn(CO)₃ Br] works effectively as a catalyst for the α-alkylation of oxindoles by both secondary as well as primary alcohols. The procedure has been used for the synthesis of pharmaceutically important recently developed oxindoles such as 3-(4-methoxybenzyl)indolin-2-one, 3-(4-(dimethylamino)benzyl)indolin-2-one, 3-(4-(dimethylamino)phenyl)-5-fluoroindolin-2-one and 3-(benzo[d][1,3]dioxol-5-ylmethyl)indolin-2-one, which are found to be effective in preventing specific types of cell death in neurodegenerative disorders. Control experiments have been carried out to investigate the reaction mechanism and the crucial role of metal-ligand cooperation via -NH₂ moiety during catalysis.

Recent Advances on Direct Functionalization of Indoles in Aqueous Media

Indoles and their derivatives have dominated a significant proportion of nitrogen-containing heterocyclic compounds and play an essential role in synthetic and medicinal chemistry, pesticides, and advanced materials. Compared with conventional synthetic strategies, direct functionalization of indoles provides straightforward access to construct diverse indole scaffolds. As we enter an era emphasizing green and sustainable chemistry, utilizing environment-friendly solvents represented by water demonstrates great potential in synthesizing valuable indole derivatives. This review aims to depict the critical aspects of aqueous-mediated indoles functionalization over the past decade and discusses the future challenges and prospects in this fast-growing field. For the convenience of readers, this review is classified into three parts according to the bonding modes (C-C, C-N, and C-S bonds), which focus on the diversity of indole derivatives, the prominent role of water in the chemical process, and the types of catalyst systems and mechanisms. We hope this review can promote the sustainable development of the direct functionalization of indoles and their derivatives and the discovery of novel and practical organic methods in aqueous phase.

Physicochemical Properties, Drug Likeness, ADMET, DFT Studies and in vitro antioxidant activity of Oxindole Derivatives

Poor pharmacokinetic and safety profiles create significant hurdles in the drug development process. This work focuses on a detailed understanding of drug discovery interplay among physicochemical, pharmacokinetic, toxicity endpoints, and antioxidant properties of oxindole derivatives. DFT compıutations were also performed at B3LYP/6-311G** level to evaluate the physicochemical properties, global reactivity features, and intramolecular interactions. The BOILED-Egg pharmacokinetic model envisaged gastrointestinal absorption, blood-brain barrier penetration, and no interaction with p-glycoprotein for compounds C1 and C2. The physicochemical evaluation revealed that C1 possesses superior drug-like properties fit for oral absorption. Both derivatives were predicted to have high plasma protein binding, efficient distribution, and inhibiting CYP 450 major isoforms but serve as substrates only for a few of them. Both molecules have mild to moderate clearance rates. Out of ten toxicity parameters, only hepatotoxicity was predicted. DFT results implied that the meta position of the -OH group made the possibility of charge transfer greater than -para positioned -OH, due to the ΔN_max (eV) values of molecules C1 and C2 being calculated at 2.596 and 2.477, respectively. Both C1 and C2 exhibited a concentration dependant DPPH and ABTS radical scavenging activity. The chemical structure-physicochemical-pharmacokinetic relationship identified the meta position as the favorite for the electron-withdrawing hydroxyl group. This provides useful insight to medicinal chemists to design 6-chlorooxindole derivatives with an acceptable drug-like and pharmacokinetic property.

Asymmetric Rubottom-Type Oxidation Catalyzed by Chiral Calcium Phosphates

A highly efficient catalytic asymmetric Rubottom-type oxidation is described. Using meta-chloroperbenzoic acid (m-CPBA) as the oxidant and chiral calcium phosphate as the catalyst, the facile transformation enables direct hydroxylation of N-Boc oxindoles and β-ketoesters in high yields (up to 99 %) and in a highly enantioenriched fashion (up to >99 % ee). The application of the established method was demonstrated by the synthesis of a pharmaceutically important 3-hydroxyoxindole with excellent enantiocontrol.

Ugi Four-Component Reactions Using Alternative Reactants

The Ugi four-component reaction (Ugi-4CR) undoubtedly is the most prominent multicomponent reaction (MCRs) that has sparked organic chemists' interest in the field. It has been widely used in the synthesis of diverse heterocycle molecules such as potential drugs, natural product analogs, pseudo peptides, macrocycles, and functional materials. The Ugi-4CRs involve the use of an amine, an aldehyde or ketone, an isocyanide, and a carboxylic acid to produce an α-acetamido carboxamide derivative, which has significantly advanced the field of isocyanide-based MCRs. The so-called intermediate nitrilium ion could be trapped by a nucleophile such as azide, N-hydroxyphthalimide, thiol, saccharin, phenol, water, and hydrogen sulfide instead of the original carboxylic acid to allow for a wide variety of Ugi-type reactions to occur.β In addition to isocyanide, there are alternative reagents for the other three components: amine, isocyanide, and aldehyde or ketone. All these alternative components render the Ugi reaction an aptly diversity-oriented synthesis of a myriad of biologically active molecules and complex scaffolds. Consequently, this review will delve deeper into alternative components used in the Ugi MCRs, particularly over the past ten years.

Practical, scalable, and transition metal-free visible light-induced heteroarylation route to substituted oxindoles

The synthetic application of (hetero)aryl radicals in organic synthesis has been known since the last century. However, their applicability has significantly suffered from ineffective generation protocols. Herein, we present a visible-light-induced transition metal-free (hetero)aryl radical generation from readily available (hetero)aryl halides for the synthesis of 3,3'-disubstituted oxindoles. This transformation is amenable to a wide range of (hetero)aryl halides as well as several easily accessible acrylamides, and it is also scalable to multigram synthesis. Finally, the versatility of the oxindole products is demonstrated through their conversion to a variety of useful intermediates applicable to target-directed synthesis.

Photoinduced halogen-bonding enabled synthesis of oxindoles and isoindolinones from aryl iodides

We report the use of halogen bonding (XB) for the generation of aryl radicals from aryl halides under blue light irradiation and applied it in radical generation/1,5-hydrogen-atom transfer/radical cyclization cascade reactions for the synthesis of oxindoles and isoindolinones. On the basis of experimental studies, we propose that DBU can serve as a suitable XB acceptor with aryl halides for the formation of a photoactive electron donor and acceptor complex.

NaI/PPh3-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

A practical NaI/PPh3-catalyzed decarboxylative radical cascade cyclization of N-arylacrylamides with redox-active esters is described, which is mediated by visible light irradiation. A wide range of substrates bearing different substituents and derived from ubiquitous carboxylic acids, including α-amino acids, were synthesized and examined under this very mild, efficient, and cost effective transition-metal-free synthetic method. These afforded various functionalized oxindoles featuring a C3 quaternary stereogenic center. Mechanistic experiments suggest a radical mechanism.

Highly efficient synthesis of C3-heteroaryl 3-fluorooxindoles via a one-pot stepwise Ce(iii)/photoassisted cross-dehydrogenative coupling/fluorooxidation process

A one-pot stepwise strategy has been developed to afford C3-heteroaryl 3-fluorooxindoles via a Ce(iii)/photoassisted cross-dehydrogenative coupling/fluorooxidation process in moderate-to-good yields with excellent functional group compatibility.

Enantioselective Synthesis of Quaternary Oxindoles: Desymmetrizing Staudinger-Aza-Wittig Reaction Enabled by a Bespoke HypPhos Oxide Catalyst

This paper describes a catalytic asymmetric Staudinger-aza-Wittig reaction of (o-azidoaryl)malonates, allowing access to chiral quaternary oxindoles through phosphine oxide catalysis. We designed a novel HypPhos oxide catalyst to enable the desymmetrizing Staudinger-aza-Wittig reaction through the PIII/PV═O redox cycle in the presence of a silane reductant and an IrI-based Lewis acid. The reaction occurs under mild conditions, with good functional group tolerance, a wide substrate scope, and excellent enantioselectivity. Density functional theory revealed that the enantioselectivity in the desymmetrizing reaction arose from the cooperative effects of the IrI species and the HypPhos catalyst. The utility of this methodology is demonstrated by the (formal) syntheses of seven alkaloid targets: (-)-gliocladin C, (-)-coerulescine, (-)-horsfiline, (+)-deoxyeseroline, (+)-esermethole, (+)-physostigmine, and (+)-physovenine.

Multicomponent reactions as a privileged tool for multitarget-directed ligand strategies in Alzheimer's disease therapy

Among neurodegenerative pathologies affecting the older population, Alzheimer's disease is the most common type of dementia and leads to neurocognitive and behavioral disorders. It is a complex and progressive age-related multifactorial disease characterized by a series of highly interconnected pathophysiological processes. Within the last decade, the multitarget-directed ligand strategy has emerged as a viable approach to developing complex molecules that exhibit several pharmacophores which can target the different enzymes and receptors involved in the pathogenesis of the disease. Herein, we focus on using multicomponent reactions such as Hantzsch, Biginelli and Ugi to develop these biologically active multitopic ligands.

The Effect of 1,2,4-Triazole-3-thiol Derivatives Bearing Hydrazone Moiety on Cancer Cell Migration and Growth of Melanoma, Breast, and Pancreatic Cancer Spheroids

4-Phenyl-3-[2-(phenylamino)ethyl]-1H-1,2,4-triazole-5(4H)-thione was used as a starting compound for the synthesis of the corresponding 1,2,4-triazol-3-ylthioacetohydrazide, which reacts with isatins and various aldehydes bearing aromatic and heterocyclic moieties provided target hydrazones. Their cytotoxicity was tested by the MTT assay against human melanoma IGR39, human triple-negative breast cancer (MDA-MB-231), and pancreatic carcinoma (Panc-1) cell lines. The selectivity of compounds towards cancer cells was also studied. In general, the synthesized compounds were more cytotoxic against the melanoma cell line. N′-(2-oxoindolin-3-ylidene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide, N′-((1H-pyrrol-2-yl)methylene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide and N′-(2-hydroxy-5-nitrobenzylidene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide were identified as the most active among all synthesized compounds in 3D cell cultures. N′-(4-(dimethylamino)benzylidene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide inhibited all cancer cell migration, was characterized as relatively more selective towards cancer cells, and could be further tested as an antimetastatic candidate.