Oxindole Scaffolds Research Articles

Ru(II)-Catalyzed Skeletal Editing of Oxindole with Internal Alkyne To Synthesize C7-Alkylated Indole Derivatives.

A Ru(II)-catalyzed skeletal editing of oxindole scaffolds was established to afford C7-alkyl acetate indole derivatives using internal alkyne and alkyl alcohol. The developed method is simple, efficient, and straightforward. The reaction was extended to substrates having wide chemoselective profiles. When unsymmetrical alkynes were used, promising regioselectivity was realized. A preliminary mechanistic study revealed that the reaction pathway proceeded by Ru(II)/Ag(I)-catalyzed amide cleavage and subsequent oxidative annulation.

Quinazoline-oxindole hybrids as angiokinase inhibitors and anticancer agents: Design, synthesis, biological evaluation, and molecular docking studies.

Two new sets of quinazoline-oxindole 8a-l and quinazoline-dioxoisoindoline 10a-d hybrids were designed as type II angiokinase inhibitors and anticancer agents. The design strategy was adjusted to account for the quinazoline scaffold's placement in the target kinases' hinge region, where it would form hydrogen bonding and hydrophobic interactions with the important amino acids to stabilize it, and the amide group's occupation in the gate region, which would direct the oxindole scaffold toward the hydrophobic back pocket. The two sets of quinazolines 8a-l and 10a-d displayed pronounced inhibitory activity on VEGFR-2 (IC50 = 0.46-2.20 µM). The quinazoline-oxindole hybrids 8d, 8f, and 8h displayed IC50 = 0.46, 0.49, and 0.49 µM, respectively. Compound 8f demonstrated potent multikinase activity with IC50 values of 0.95 and 0.67 µM against FGFR-1 and BRAF, respectively. Additionally, compound 8f showed significant anticancer activity against National Cancer Institute's cancer cell lines, with GI50 reaching 1.21 µM. Analysis of the impact of compound 8f on the MDA-MB-231 cell line's cell cycle and apoptosis revealed that 8f stalled the cell cycle at the G2/M phase and promoted its necrosis.

Facile Synthesis of Spirocyclic Oxindole Scaffolds via Intermolecular [4 + 1] Cycloaddition of ortho-Quinone Methides with 3-Chlorooxindoles

Facile Synthesis of Spirocyclic Oxindole Scaffolds via Intermolecular [4 + 1] Cycloaddition of ortho-Quinone Methides with 3-Chlorooxindoles

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.

Base catalyzed abnormal [3+2]-cycloaddition reaction of isatin N,N′‑cyclic azomethine imine with malononitrile via C-3 umpolung of oxindole

In this paper, we described a base promoted annulation reaction of isatin N,N'-cyclic azomethine imine and malononitrile for the synthesis of 1′,2′-dihydrospiro[indoline-3,6′-pyrrolo[1,2-b]pyrazole] derivatives using a new abnormal [3 + 2]-cycloaddition reaction. A variety of pyrrolo-pyrazole bearing oxindole scaffolds with medicinal capability were synthesized in moderate to high yields via C3 umpolung of oxindole.

Engaging Isatins and Amino Acids in Multicomponent One-Pot 1,3-Dipolar Cycloaddition Reactions-Easy Access to Structural Diversity.

Multicomponent reactions (MCRs) have undoubtedly emerged as the most indispensable tool for organic chemists worldwide, finding extensive utility in the synthesis of intricate natural products, heterocyclic molecules with significant bioactivity, and pharmaceutical agents. The multicomponent one-pot 1,3-dipolar cycloaddition reactions, which were initially conceptualized by Rolf Huisgen in 1960, find extensive application in contemporary heterocyclic chemistry. In terms of green synthesis, the multicomponent 1,3-dipolar cycloaddition is highly favored owing to its numerous advantages, including high step- and atom-economies, remarkable product diversity, as well as excellent efficiency and diastereoselectivity. Among the numerous pieces of research, the most fascinating reaction involves the utilization of azomethine ylides generated from isatins and amino acids that can be captured by various dipolarophiles. This approach offers a highly efficient and convenient method for constructing spiro-pyrrolidine oxindole scaffolds, which are crucial building blocks in biologically active molecules. Consequently, this review delves deeper into the dipolarophiles utilized in the 1,3-dipolar cycloaddition of isatins and amino acids over the past six years.

An Efficient Approach Towards the Synthesis of Nintedanib

AbstractNintedanib, a potent, oral, small‐molecule tyrosine kinase inhibitor, is known as a triple angiokinase inhibitor, inhibiting three major signaling pathways in angiogenesis. Here, we report full details of the alternative path toward the synthesis of nintedanib via novel intermediates. A key feature of our approach is the stereoselective intramolecular cyclization strategy that enables the concise conversion of β‐keto amide into a 3‐acyloxindole derivative, which is an important scaffold for nintedanib synthesis. Subsequent condensation of oxindole scaffold with synthesized amine derivative led to the drug nintedanib with good yields.

Microwave-Assisted Synthesis of 3-Hydroxy-2-oxindoles and Pilot Evaluation of Their Antiglaucomic Activity.

Glaucoma is a widespread neurodegenerative disease for which increased intraocular pressure (IOP) is a primary modifiable risk factor. Recently, we have observed that compounds with oxindole scaffolds are involved in the regulation of intraocular pressure and therefore have potential antiglaucomic activity. In this article, we present an efficient method for obtaining novel 2-oxindole derivatives via microwave-assisted (MW) decarboxylative condensation of substituted isatins with malonic and cyanoacetic acids. Various 3-hydroxy-2-oxindoles were synthesized using MW activation for 5-10 min with high yields (up to 98%). The influence of novel compounds applied in instillations on IOP was studied in vivo on normotensive rabbits. The lead compound was found to reduce the IOP by 5.6 Torr (ΔIOP for the widely used antiglaucomatousic drug timolol 3.5 Torr and for melatonin 2.7 Torr).

2-Oxindole and related heterocycles: synthetic methodologies for their natural products and related derivatives.

Natural goods, medications, and pharmaceutically active substances all contain substituted oxindoles. Generally, the C-3 stereocenter of the substituents of oxindoles and their absolute arrangement have a substantial impact on the bioactivity of these substances. In this case, the desire for contemporary probe and drug-discovery programs for the synthesis of chiral compounds using desirable scaffolds with high structural diversity further drives research in this field. Also, the new synthetic techniques are generally simple to apply for the synthesis of other similar scaffolds. Herein, we review the distinct approaches for the synthesis of diverse useful oxindole scaffolds. Specifically, the research findings on the naturally existing 2-oxindole core and a variety of synthetic compounds having a 2-oxindole core are discussed. We present an overview of the construction of oxindole-based synthetic and natural products. In addition, the chemical reactivity of 2-oxindole and its related derivatives in the presence of chiral and achiral catalysts are thoroughly discussed. The data compiled herein provides broad information related to the bioactive product design, development, and applications of 2-oxindoles and the reported techniques will be helpful for the investigation of novel reactions in the future.

In Silico Screening for Novel Tyrosine Kinase Inhibitors with Oxindole Scaffold as Anti-Cancer Agents: Design, QSAR Analysis, Molecular Docking and ADMET Studies

Recently, anti-cancer targeting drugs are directed against specific molecules and signaling pathways. These targeting agents have reasonable specificity, efficacy and less side effects. Tyrosine kinases, which play an essential role in growth factor signaling regulation, are significant targets in this type of therapy. Synthesized numerous tyrosine-kinase inhibitors (TKIs), such as substituted indolin-2-ones, are effective as anti-tumor and anti-leukemia agents. In this study, a series of novel substituted indolin-2-ones were studied as kinase inhibitor analogs through quantitative structure–activity relationship (QSAR) analysis. Two chemometrics methods, such as multiple linear regression (MLR) and partial least squares combined with genetic algorithm for variable selection (GA-PLS), were employed to establish relationships between structural characteristics and kinase inhibitory activity of used oxindole analogs. The GA-PLS was developed as the best predictor and validated QSAR model. The data set compounds were also studied by molecular docking to investigate their binding mechanism in the active site of tyrosine kinase enzyme. According to the information obtained from QSAR models and molecular docking analysis, 40 new potent lead compounds with novel structural features were introduced. Molecular docking, drug-likeness rules, ADMET analysis, bioavailability, toxicity prediction and target identification were carried out on the newly designed oxindoles to elucidate fundamental structural properties that affect their inhibitory activity.

Identification of potential biological targets of oxindole scaffolds via in silico repositioning strategies.

Background: Drug repurposing is an alternative strategy to traditional drug discovery that aims at predicting new uses for already existing drugs or clinical candidates. Drug repurposing has many advantages over traditional drug development, such as reduced attrition rates, time and costs. This is especially the case considering that most drugs investigated for repurposing have already been assessed for their safety in clinical trials. Repurposing campaigns can also be designed for libraries of already synthesized molecules at different levels of biological experimentation, from null to in vitro and in vivo. Such an extension of the "repurposing" concept is expected to provide significant advantages for the identification of novel drugs, as the synthetic accessibility of the desired compounds is often one of the limiting factors in the traditional drug discovery pipeline. Methods: In this work, we performed a computational repurposing campaign on a library of previously synthesized oxindole-based compounds, in order to identify potential new targets for this versatile scaffold. To this aim, ligand-based approaches were firstly applied to evaluate the similarity degree of the investigated compound library, with respect to ligands extracted from the DrugBank, Protein Data Bank (PDB) and ChEMBL databases. In particular, the 2D fingerprint-based and 3D shape-based similarity profiles were evaluated and compared for the oxindole derivates. Results: The analyses predicted a set of potential candidate targets for repurposing, some of them emerging by consensus of different computational analyses. One of the identified targets, i.e., the vascular endothelial growth factor receptor 2 (VEGFR-2) kinase, was further investigated by means of docking calculations, followed by biological testing of one candidate. Conclusions: While the compound did not show potent inhibitory activity towards VEGFR-2, the study highlighted several other possibilities of therapeutically relevant targets that may be worth of consideration for drug repurposing.

Identification of potential biological targets of oxindole scaffolds via in silico repositioning strategies

Background: Drug repurposing is an alternative strategy to traditional drug discovery that aims at predicting new uses for already existing drugs or clinical candidates. Drug repurposing has many advantages over traditional drug development, such as reduced attrition rates, time and costs. This is especially the case considering that most drugs investigated for repurposing have already been assessed for their safety in clinical trials. Repurposing campaigns can also be designed for libraries of already synthesized molecules at different levels of biological experimentation, from null to in vitro and in vivo. Such an extension of the “repurposing” concept is expected to provide significant advantages for the identification of novel drugs, as the synthetic accessibility of the desired compounds is often one of the limiting factors in the traditional drug discovery pipeline. Methods: In this work, we performed a computational repurposing campaign on a library of previously synthesized oxindole-based compounds, in order to identify potential new targets for this versatile scaffold. To this aim, ligand-based approaches were firstly applied to evaluate the similarity degree of the investigated compound library, with respect to ligands extracted from the DrugBank, Protein Data Bank (PDB) and ChEMBL databases. In particular, the 2D fingerprint-based and 3D shape-based similarity profiles were evaluated and compared for the oxindole derivates. Results: The analyses predicted a set of potential candidate targets for repurposing, some of them emerging by consensus of different computational analyses. One of the identified targets, i.e., the vascular endothelial growth factor receptor 2 (VEGFR-2) kinase, was further investigated by means of docking calculations, followed by biological testing of one candidate. Conclusions: While the compound did not show potent inhibitory activity towards VEGFR-2, the study highlighted several other possibilities of therapeutically relevant targets that may be worth of consideration for drug repurposing.

Survey of New, Small-Molecule Isatin-Based Oxindole Hybrids as Multi-Targeted Drugs for the Treatment of Alzheimer’s Disease

AbstractIn the last decade, our group has been very active at developing and assaying complex libraries of scaffolds with a focus on their potential to identify bioactive drug candidates for neurodegenerative diseases, particularly Alzheimer’s disease (AD). Attention has been focused on isatin-based oxindole scaffolds, for which promising results concerning butyrylcholinesterase (BuChE) inhibitory activity have previously been obtained. Considering some published reports and detailed analysis of the pharmacophores of commercially available drugs for AD (powerful cholinesterase (ChE) inhibitors), we performed a strategic structural modification of the isatin core and generated a new family of isatin-based oxindole hybrids (27 new compounds) possessing crucial key functional units in their framework. The syntheses were accomplished using multiple approaches, including simple N-alkylation reactions, copper-catalyzed amination reactions, and click chemistry. The resulting library was evaluated on ChE and MAO enzymes, both of which are involved in the pathophysiology of neurodegeneration. IC50 values of 1.6 and 2.6 μM (BuChE assays), were achieved for the best inhibitors.

A Phosphine-Mediated Dearomative Skeletal Rearrangement of Dianiline Squaraine Dyes.

A phosphorus(III)-mediated dearomatization of ortho-substituted dianiline squaraine dyes results in an unusual skeletal rearrangement to provide exotic, highly conjugated benzofuranone and oxindole scaffolds bearing a C3 side chain comprised of a linear conflagration of an enol, a phosphorus ylide, and 2,4-disubstituted aniline. Employing experimental and computational analysis, a mechanistic evaluation revealed a striking dependence on the acidity of the aniline ortho substituent. Notably, the rearrangement adducts underwent rapid and complete reversion to the parent squaraine in the presence of a Brønsted acid.

A formal intermolecular [4 + 1] cycloaddition reaction of 3-chlorooxindole and o-quinone methides: a facile synthesis of spirocyclic oxindole scaffolds.

Herein, we developed an efficient and straightforward method for the rapid synthesis of spirocyclic oxindole scaffolds via the [4 + 1] cyclization reaction of 3-chlorooxindole with o-quinone methides (o-QMs), which were generated under mild conditions. The products could be obtained in excellent yields with numerous types of 3-chlorooxindole. This methodology features mild reaction conditions, high atom-economy and broad substrate scope.

Palladium‐Catalyzed Regioselective Domino Spirocyclization of Carbamoyl Chlorides with Alkynes and Benzynes

AbstractA palladium‐catalyzed domino spiro‐cyclization of carbamoyl chlorides with alkynes and benzynes, involving intramolecular C−H activation to afford valuable oxindole scaffolds bearing spiro quaternary stereocenters, has been developed. This one‐step synthesis of spirooxindole is both step‐ and atom‐economic, proceeding with high regioselectivity in moderate to excellent yields.magnified image

Organocatalytic enantioselective conjugate addition of nitroalkanes to trifluoromethylated 3-methyleneoxindoles

A bifunctional squaramide catalyzed asymmetric conjugate addition of nitroalkanes to trifluoromethylated 3-methyleneoxindoles was developed, and a range of trifluoromethyl containing oxindole derivatives were obtained with generally high yields and enantioselectivities. The nitro functionality and oxindole scaffold in the corresponding products are versatile building blocks that readily enable many further valuable transformations.

Metal-Catalyzed Approaches toward the Oxindole Core.

The oxindole scaffold is a privileged structural motif that is found in a variety of bioactive targets and natural products. Moreover, derivatives of the oxindole structure are widely present in a number of biologically relevant compounds and are key intermediates in the synthesis of diverse natural products and pharmaceuticals. Therefore, novel methods to obtain oxindoles remain of high priority in synthetic organic chemistry.Over the past several decades, novel transition-metal-catalyzed methodologies have been applied toward the synthesis of a variety of heterocycles. A detailed mechanistic understanding facilitates the disruption of traditional catalytic pathways to access useful synthetic intermediates. The strategies employed have generally revolved around the generation of high-energy organometallic intermediates, which undergo cyclization reactions through domino processes. Domino cyclization methodologies are therefore attractive, as they allow facile access to functionalized oxindoles containing all-carbon quaternary centers or tetrasubstituted olefins with high chemo- and stereoselectivities. Furthermore, these developed synthetic strategies can often be easily applied in the syntheses of other related scaffolds.In this Account, we discuss the three unique strategies that our group has leveraged for the synthesis of valuable oxindole scaffolds. The first section in this Account outlines the use of an initial oxidative addition to a C(sp2)-X bond, followed by a migratory insertion, yielding a neopentyl species amenable to a variety of subsequent functionalizations. From this reactive neopentyl metal species, we have reported C-X reductive eliminations, anionic capture cascade reactions, and intramolecular C-H functionalization processes. The second section of this Account summarizes our group's findings on 1,2-insertions of a metal-nucleophile species across an unsaturation, generating a reactive organometallic intermediate; subsequent reactions with tethered electrophiles form the desired heterocyclic core. We have explored a wide array of transition metal-catalyzed strategies using this approach, including rhodium-catalyzed conjugate additions, an asymmetric copper-catalyzed borylcupration, and a palladium(II)-catalyzed chloropalladation protocol. The final section of this Account details the use of dual-metal catalysis to perform a cyclization through a C-H functionalization-allylation domino reaction. Throughout this Account, we provide details of mechanistic studies that better enabled our understanding of the domino processes.Overall, our group has developed methods exploiting the unique reactivity of palladium, nickel, copper, rhodium, and ruthenium catalysts to develop methods toward a wide array of oxindole scaffolds. On the basis of the utility, diversity, and applicability of the strategies developed, we believe that they will prove to be highly useful in the syntheses of other important targets and inspire further development and mechanistic understanding of various metal-catalyzed processes.

Exploration of dual fatty acid amide hydrolase and cholinesterase inhibitory potential of some 3‐hydroxy‐3‐phenacyloxindole analogs

The dual inhibition of fatty acid amide hydrolase (FAAH) and cholinesterases (ChEs) has recently egressed as a novel strategy for the management of neurodegeneration. In the present work, a library of 3-hydroxy-3-phenacyloxindole analogs was screened for FAAH and ChEs (acetylcholinesterase [AChE]/butyrylcholinesterase [BuChE]) inhibition. 1-Benzyl-3-hydroxy-3-(2',4'-dibromophenacyl)oxindole (16), the most promising compound, showed a balanced multifunctional profile with FAAH (IC50 = 8.7 ± 0.3 nM, competitive and reversible), AChE (IC50 = 28 ± 3 nM, mixed and reversible), and BuChE (IC50 = 65 ± 8 nM, mixed and reversible) inhibition. The structure-activity relationship study predicted multifarious fundamental aspects crucial for the potency of these analogs. Furthermore, the structural geometry and rigidness bestowed by the oxindole moiety resulted in improved adherence of the compounds within the binding pockets of the target enzymes. Molecular docking studies of the docked conformations acknowledged numerous interactions for trenchant stabilization of inhibitor-enzyme complexes. Binding interaction and conformational alignment studies of stereoisomers of the lead inhibitors highlighted the importance of the (S)-stereochemistry at C-3 of the oxindole scaffold for potency and selectivity. Compound 16 also displayed an antioxidant potential surpassing that of ascorbic acid, and it was non-neurotoxic. In silico molecular and ADMET properties anticipated druglikeness of the test compounds for oral use. Thus, compound 16 emerged as a new and interesting multifaceted candidate that could further be explored for its potential multitargeted role in the discovery of drugs for the treatment of Alzheimer's disease.

Microwave‐Assisted Regioselective Friedel–Crafts Arylation by BF3 ⋅ OEt2: A Facile Synthetic Access to 3‐Substituted‐3‐Propargyl Oxindole Scaffolds

AbstractA facile microwave‐assisted synthetic strategy for the construction of C–C bond via regioselective Friedel–Crafts arylation of 3‐hydroxy‐3‐phenylethynyl oxindoles with different electron‐rich nucleophiles such as phenols, sulphonamides, anisole, benzofuran, and benzothiophene has been established by employing BF3 ⋅ OEt2 as catalyst. The current protocol attributes mild conditions, cost‐effective, transition‐metal free synthesis, wide substrate scope and moderate to good yields. Moreover, this method is amenable for the generation of a library of densely substituted 3‐(4‐hydroxyphenyl)‐3‐(phenylethynyl) oxindoles and 3‐(4‐benzenesulphonamide)‐3‐(phenylethynyl) oxindoles as privileged scaffolds.