C3-Spirooxindoles: Divergent chemical synthesis and bioactivities (2018-2023).

This scientific review documents the recent progress of C3-spirooxindoles chemistry (synthesis and reaction mechanism) and their bioactivities, focusing on the promising results as well as highlighting the biological mechanism via the reported molecular docking findings of the most bioactive derivatives. C3-Spirooxindoles are attractive bioactive agents and have been found in a variety of natural compounds, including alkaloids. They are widely investigated in the field of medicinal chemistry and play a key role in medication development, such as antivirals, anticancer agents, antimicrobials, etc. Regarding organic synthesis, several traditional and advanced strategies have been reported, particularly those that started with isatin derivatives.

Enantioselective formal total synthesis of dihydrospirotryprostatin B.

Spirotryprostatins are representative members of medicinally interesting bioactive molecules of the spirooxindole natural products. In this communication, we present a novel enantioselective total synthesis of the spirooxindole alkaloid dihydrospirotryprostatin B. The synthesis takes advantage of copper-catalyzed tandem reaction of o-iodoanilide chiral sulfinamide derivatives with alkynone to rapidly construct the key quaternary carbon stereocenter of the natural product dihydrospirotryprostatin B.

Novel spirooxindole alkaloid derivatives from the medicinal insect Blaps japanensis and their biological evaluation.

Blapspirooxindoles A-C (1-3), three novel spirooxindole alkaloids with a unique spiro[chromane-4,3'-indoline]-2,2'-dione motif, blapcumaranons A and B (4 and 5), two new 2-cumaranon derivatives, blapoxindoles A-J (6-15), ten new oxindole alkaloid derivatives, along with one known compound (16), were isolated from the whole bodies of Blaps japanensis. Their structures including absolute configurations were determined by using spectroscopic, X-ray crystallographic, and computational methods. Compounds 1-11 and 13 exist as racemic mixtures in nature, and their (-)- and (+)-antipodes were separated by chiral HPLC. Biological evaluations of these compounds were determined with multiple assays including anti-tumor, anti-inflammatory, and renal protection activities in vitro. Several compounds displayed effective activity in one or more assays.

1,3-Dipolar cycloaddition reactions of isatin-derived azomethine ylides for the synthesis of spirooxindole and indole-derived scaffolds: recent developments.

The unique therapeutic and biological characteristics of spirooxindole have led to the presentation of numerous reactions for the synthesis of spirooxindoles through 1,3-Dipolar cycloaddition of highly reactive isatin-derived azomethine ylides with activated olefins as the main tool for the formation of spirocyclic oxindoles during the last 4 years. Therefore, there is a need to highlight the recent developments in this area, along with the representative synthetic methods and relevant reaction mechanisms from 2018 to 2021. The representative synthetic methodologies were listed in four sections based on the procedure to form the azomethine ylide species including isatins and amino acids, isatin-derived α-(trifluoromethyl)imine, isatins and benzylamines, and from isatin-derived cyclic imine 1,3-dipoles.

Dipolarophile-Controlled Regioselective 1,3-Dipolar Cycloaddition: A Switchable Divergent Access to Functionalized N-Fused Pyrrolidinyl Spirooxindoles.

N-fused pyrrolidinyl spirooxindole belongs to a class of privileged heterocyclic scaffolds and is prevalent in natural alkaloids and synthetic pharmaceutical molecules. To realize the switchable synthesis of divergent N-fused pyrrolidinyl spirooxindoles for further biological activity evaluation via a substrate-controlled strategy, a chemically sustainable, catalysis-free, and dipolarophile-controlled three-component 1,3-dipolar cycloaddition of isatin-derived azomethine ylides with diverse dipolarophiles is described in this work. A total of 40 functionalized N-fused pyrrolidinyl spirooxindoles were synthesized in 76-95% yields with excellent diastereoselectivities (up to >99:1 dr). The scaffolds of these products can be well-controlled by employing different 1,4-enedione derivatives as dipolarophiles in EtOH at room temperature. This study provides an efficient strategy to afford a spectrum of natural-like and potentially bioactive N-fused pyrrolidinyl spirooxindoles.

Chemo-/Regio-Selective Synthesis of Novel Functionalized Spiro[pyrrolidine-2,3'-oxindoles] under Microwave Irradiation and Their Anticancer Activity.

A novel series of nitrostyrene-based spirooxindoles were synthesized via the reaction of substituted isatins 1a-b, a number of α-amino acids 2a-e and (E)-2-aryl-1-nitroethenes 3a-e in a chemo/regio-selective manner using [3+2] cycloaddition (Huisgen) reaction under microwave irradiation conditions. The structure elucidation of all the synthesized spirooxindoles were done using 1H and 13C NMR and HRMS spectral analysis. The single crystal X-ray crystallographic study of compound 4l was used to assign the stereochemical arrangements of the groups around the pyrrolidine ring in spiro[pyrrolidine-2,3'-oxindoles] skeleton. The in vitro anticancer activity of spiro[pyrrolidine-2,3'-oxindoles] analogs 4a-w against human lung (A549) and liver (HepG2) cancer cell lines along with immortalized normal lung (BEAS-2B) and liver (LO2) cell lines shows promising results. Out of the 23 synthesized spiro[pyrrolidine-2,3'-oxindoles], while five compounds (4c, 4f, 4m, 4q, 4t) (IC50 = 34.99-47.92 µM; SI = 0.96-2.43) displayed significant in vitro anticancer activity against human lung (A549) cancer cell lines, six compounds (4c, 4f, 4k, 4m, 4q, 4t) (IC50 = 41.56-86.53 µM; SI = 0.49-0.99) displayed promising in vitro anticancer activity against human liver (HepG2) cancer cell lines. In the case of lung (A549) cancer cell lines, these compounds were recognized to be more efficient and selective than standard reference artemisinin (IC50 = 100 µM) and chloroquine (IC50 = 100 µM; SI: 0.03). However, none of them were found to be active as compared to artesunic acid [IC50 = 9.85 µM; SI = 0.76 against lung (A549) cancer cell line and IC50 = 4.09 µM; SI = 2.01 against liver (HepG2) cancer cell line].

Spirooxindole: A Versatile Biologically Active Heterocyclic Scaffold.

Spirooxindoles occupy an important place in heterocyclic chemistry. Many natural spirooxindole-containing compounds have been identified as bio-promising agents. Synthetic analogs have also been synthesized utilizing different pathways. The present article summarizes the recent development of both natural and synthetic spirooxindole-containing compounds prepared from isatin or its derivatives reported in the last five years. The spirooxindoles are categorized based on their mentioned biological properties.

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.

Natural-Product-Inspired Microwave-Assisted Synthesis of Novel Spirooxindoles as Antileishmanial Agents: Synthesis, Stereochemical Assignment, Bioevaluation, SAR, and Molecular Docking Studies.

Leishmaniasis is a neglected tropical disease, and there is an emerging need for the development of effective drugs to treat it. To identify novel compounds with antileishmanial properties, a novel series of functionalized spiro[indoline-3,2'-pyrrolidin]-2-one/spiro[indoline-3,3'-pyrrolizin]-2-one 23a-f, 24a-f, and 25a-g were prepared from natural-product-inspired pharmaceutically privileged bioactive sub-structures, i.e., isatins 20a-h, various substituted chalcones 21a-f, and 22a-c amino acids, via 1,3-dipolar cycloaddition reactions in MeOH at 80 °C using a microwave-assisted approach. Compared to traditional methods, microwave-assisted synthesis produces higher yields and better quality, and it takes less time. We report here the in vitro antileishmanial activity against Leishmania donovani and SAR studies. The analogues 24a, 24e, 24f, and 25d were found to be the most active compounds of the series and showed IC50 values of 2.43 µM, 0.96 µM, 1.62 µM, and 3.55 µM, respectively, compared to the standard reference drug Amphotericin B (IC50 = 0.060 µM). All compounds were assessed for Leishmania DNA topoisomerase type IB inhibition activity using the standard drug Camptothecin, and 24a, 24e, 24f, and 25d showed potential results. In order to further validate the experimental results and gain a deeper understanding of the binding manner of such compounds, molecular docking studies were also performed. The stereochemistry of the novel functionalized spirooxindole derivatives was confirmed by single-crystal X-ray crystallography studies.

Morphological Profiling Identifies the Motor Protein Eg5 as Cellular Target of Spirooxindoles.

Oxindoles and iso-oxindoles are natural product-derived scaffolds that provide inspiration for the design and synthesis of novel biologically relevant compound classes. Notably, the spirocyclic connection of oxindoles with iso-oxindoles has not been explored by nature but promises to provide structurally related compounds endowed with novel bioactivity. Therefore, methods for their efficient synthesis and the conclusive discovery of their cellular targets are highly desirable. We describe a selective RhIII -catalyzed scaffold-divergent synthesis of spirooxindole-isooxindoles and spirooxindole-oxindoles from differently protected diazooxindoles and N-pivaloyloxy aryl amides which includes a functional group-controlled Lossen rearrangement as key step. Unbiased morphological profiling of a corresponding compound collection in the Cell Painting assay efficiently identified the mitotic kinesin Eg5 as the cellular target of the spirooxindoles, defining a unique Eg5 inhibitor chemotype.

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates.

A straightforward synthetic protocol for the efficient construction of diazepine-containing spiroindolines has been developed and proceeds through a by base-promoted annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates. The reaction mechanism of this formal [4 + 3] annulation includes the in situ generated allylic ylide, nucleophilic substitution, Michael additon, and elimination processes. Additionally, the similar reaction with α-halogenated N-tosylhydrazones also afforded N-tosyl-substituted spiro[indoline-3,5'-[1,2]diazepine] in satisfactory yields. This protocol provides a convenient approach for the assembly of diverse highly functionalized spiro[indoline-3,5'-[1,2]diazepines] and also features a broad substrate scope, simple reaction conditions, and high molecular convergence.

Selective construction of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] via three-component reaction.

A convenient synthetic procedure for the construction of novel dispirooxindole motifs was successfully developed by base-promoted three-component reaction of ammonium acetate, isatins and in situ-generated 3-isatyl-1,4-dicarbonyl compounds. The piperidine-promoted three-component reaction of ammonium acetate, isatins and the in situ-generated dimedone adducts of 3-ethoxycarbonylmethyleneoxindoles afforded mutlifunctionalized dispiro[indoline-3,2'-quinoline-3',3''-indoline] derivatives in good yields and with high diastereoselectivity. On the other hand, a similar reaction of the dimedone adducts of 3-phenacylideneoxindoles afforded unique dispiro[indoline-3,2'-pyrrole-3',3''-indoline] derivatives with a cyclohexanedione substituent. A plausible reaction mechanism is proposed to explain the formation of the different spirooxindoles.

Discovery of natural product-like spirooxindole derivatives as highly potent and selective LSD1/KDM1A inhibitors for AML treatment.

Histone lysine specific demethylase 1 (LSD1) is a promising new therapeutic target for cancer therapy. Following the work on the discovery of natural LSD1 inhibitor higenamine, we herein performed further structure-based design, synthesis, and extensive structure-activity relationship (SAR) studies, affording structurally new spirooxindole derivatives. Particularly, FY-56 was identified to be a highly potent LSD1 inhibitor (IC50 = 42 nM) and showed high selectivity over monoamine oxidases (MAO-A/B). Mechanistic studies showed that FY-56 moderately inhibited the proliferation and clone formation of leukemia cells, induced H3K4me1/2 accumulation and p53 activation as well as reduced the mRNA levels of the transcription factors HOXA9 and MEIS1. Meanwhile, FY-56 induced differentiation of MOLM-13 and MV4-11 cells, accompanied by an enhanced percentage of markers characteristic to differentiated macrophages and monocytes. Further in vivo studies showed that FY-56 obviously reduced the proportion of CD45+/CD33+ leukocytes in peripheral blood and spleen, and significantly prolonged the survival rate of mice. Collectively, FY-56 represents a structurally novel, highly potent and selective LSD1 inhibitor and exhibits therapeutic promise for AML treatment. The spirooxindole scaffold derived from FY-56 could be used to design structurally new LSD1 inhibitors for treating human diseases.

Novel spirooxindole based benzimidazole scaffold: In vitro, nanoformulation and in vivo studies on anticancer and antimetastatic activity of breast adenocarcinoma.

The present work provided in vitro anticancer investigation of novel spirooxindole based benzimidazole scaffold SP1 and its nanoformulation with in vivo evaluation of anticancer and antimetastatic activity as potential drug for breast adenocarcinoma. The synthesized compound SP1 exhibited potent growth inhibitory efficacy against four types of human cancer (breast, prostate, colon and lung) cell lines with IC50 = 2.4, 3.4, 7.24 and 7.81 µM and selectivity index 5.79, 4.08, 1.93 and 1.78 respectively. Flow cytometric analysis illustrated that SP1 exhibited high apoptotic effect on all tested cancer cell lines (38.22-52.3 %). The mode of action of this promising compound was declared by its ability to upregulate the gene expression of p21 (2.29-3.91 folds) with suppressing cyclin D (1.9-8.93 folds) and NF-κB (1.26-1.44 fold) in the treated cancer cells. Also, it enhanced the protein expression of apoptotic marker p53 and moderate binding affinity for MDM2 (KD;7.94 µM). Notwithstanding these promising impressive findings, its selectivity against cancer cell lines and safety on normal cells were improved by nanoformulation. Therefore, SP1 was formulated as ultra-flexible niosomal nanovesicles (transethoniosomes). The ultra-deformability is attributable to the synergism between ethanol and edge activators in improving the flexibility of the nanovesicular membrane. F8 exhibited high deformability index (DI) of (23.48 ± 1.4). It was found that % SP1 released from the optimized transethoniosomal formula (F8) after 12 h (Q12h) was 84.17 ± 1.29 % and its entrapment efficiency (%EE) was 76.48 ± 1.44 %. Based upon the very encouraging and promising in vitro results, an in vivo study was carried out in female Balb/c mice weighing (15-25 g). SP1 did halt the proliferation of breast cancer cells as well as suppressed the metastasis in other organs like liver, lung and heart.

Anticonvulsant activity, molecular modeling and synthesis of spirooxindole-4H-pyran derivatives using a novel reusable organocatalyst.

Fifteen derivatives of spirooxindole-4H-pyran (A1-A15) were subjected to evaluate through intravenous infusion of pentylenetetrazole (PTZ)-induced epilepsy mouse models. Four doses of the compounds (20, 40, 60 and 80 mg/kg) were tested in comparison with diazepam as positive control. The resulted revealed that compounds A3 and A12 were the most active compounds and indicated significant anticonvulsant activity in the PTZ test. The tested compounds were prepared via a multicomponent reaction using graphene oxide (GO) based on the 1-(2-aminoethyl) piperazine as a novel heterogeneous organocatalyst. The prepared catalyst (GO-A.P.) was characterized using some diverse microscopic and spectroscopic procedures as well. The results showed high catalytic activity of the catalyst in the synthesis of spirooxindole-4H-pyran derivatives. The GO-A.P. catalyst was reusable at least for 5 times with no significant decrease in its catalytic action. In silico assessment of physicochemical activity of all compounds also were done which represented appropriate properties. Finally, molecular docking study was performed to achieve their binding affinities as γ-aminobutyric acid-A (GABA-A) receptor agonists as a plausible mechanism of their anticonvulsant action. Binding free energy values of the compounds represented strongly matched with biological activity.

Design, Synthesis and In Vitro Evaluation of Spirooxindole-Based Phenylsulfonyl Moiety as a Candidate Anti-SAR-CoV-2 and MERS-CoV-2 with the Implementation of Combination Studies.

The search for an effective anti-viral to inhibit COVID-19 is a challenge for the specialized scientific research community. This work investigated the anti-coronavirus activity for spirooxindole-based phenylsulfone cycloadducts in a single and combination protocols. The newly designed anti-SARS-CoV-2 therapeutics spirooxindoles synthesized by [3 + 2] cycloaddition reactions represent an efficient approach. One-pot multicomponent reactions between phenyl vinyl sulfone, substituted isatins, and amines afforded highly stereoselective anti-SARS-CoV-2 therapeutics spirooxindoles with three stereogenic centers. Herein, the newly synthesized spirooxindoles were assessed individually against the highly pathogenic human coronaviruses and proved to be highly potent and safer. Interestingly, the synergistic effect by combining the potent, tested spirooxindoles resulted in an improved antiviral activity as well as better host-cell safety. Compounds 4i and 4d represented the most potent activity against MERS-CoV with IC50 values of 11 and 23 µM, respectively. Both compounds 4c and 4e showed equipotent activity with the best IC50 against SARS-CoV-2 with values of 17 and 18 µM, respectively, then compounds 4d and 4k with IC50 values of 24 and 27 µM, respectively. Then, our attention oriented to perform a combination protocol as anti-SARS-CoV-2 for the best compounds with a different binding mode and accompanied with different pharmacophores. Combination of compound 4k with 4c and combination of compounds 4k with 4i proved to be more active and safer. Compounds 4k with 4i displayed IC50 = 3.275 µM and half maximal cytotoxic-concentration CC50 = 11832 µM. MD simulation of the most potential compounds as well as in silico ADMET properties were investigated. This study highlights the potential drug-like properties of spirooxindoles as a cocktail anti-coronavirus protocol.

Synthesis and Structure Elucidation of Novel Spirooxindole Linked to Ferrocene and Triazole Systems via [3 + 2] Cycloaddition Reaction.

In the present work, a novel heterocyclic hybrid of a spirooxindole system was synthesized via the attachment of ferrocene and triazole motifs into an azomethine ylide by [3 + 2] cycloaddition reaction protocol. The X-ray structure of the heterocyclic hybrid (1″R,2″S,3R)-2″-(1-(3-chloro-4-fluorophenyl)-5-methyl-1H-1,2,3-triazole-4-carbonyl)-5-methyl-1″-(ferrocin-2-yl)-1″,2″,5″,6″,7″,7a″-hexahydrospiro[indoline-3,3″-pyrrolizin]-2-one revealed very well the expected structure, by using different analytical tools (FTIR and NMR spectroscopy). It crystallized in the triclinic-crystal system and the P-1-space group. The unit cell parameters are a = 9.1442(2) Å, b = 12.0872(3) Å, c = 14.1223(4) Å, α = 102.1700(10)°, ß = 97.4190(10)°, γ = 99.1600(10)°, and V = 1484.81(7) Å3. There are two molecules per unit cell and one formula unit per asymmetric unit. Hirshfeld analysis was used to study the molecular packing of the heterocyclic hybrid. H···H (50.8%), H···C (14.2%), Cl···H (8.9%), O···H (7.3%), and N···H (5.1%) are the most dominant intermolecular contacts in the crystal structure. O···H, N···H, H···C, F···H, F···C, and O···O are the only contacts that have the characteristic features of short and significant interactions. AIM study indicated predominant covalent characters for the Fe-C interactions. Also, the electron density (ρ(r)) at the bond critical point correlated inversely with the Fe-C distances.

Copper-catalyzed multicomponent reactions for the efficient synthesis of diverse spirotetrahydrocarbazoles.

In the presence of copper sulfate, three- or four-component reactions of 2-methylindole, aromatic aldehydes and various cyclic dienophiles in refluxing toluene afforded diverse spirotetrahydrocarbazoles. This reaction is an important development of the Levy reaction by using 2-methylindole to replace ethyl indole-2-acetate and successfully provides facile access to important polysubstituted spiro[carbazole-3,3'-indolines], spiro[carbazole-2,3'-indolines], spiro[carbazole-3,5'-pyrimidines] and spiro[carbazole-3,1'-cycloalkanes] in satisfactory yields and with high diastereoselectivity.

One-pot double annulations to confer diastereoselective spirooxindolepyrrolothiazoles.

A novel four-component reaction in one pot as an atom- and step-economic process was developed to synthesize diastereoselectively spirooxindolepyrrolothiazoles through sequential N,S-acetalation of aldehydes with cysteine and decarboxylative [3 + 2] cycloaddition with olefinic oxindoles. High synthetic efficiency, operational simplification and reaction process economy using EtOH as solvent, and only releasing CO2 and H2O as side products confer this approach favorable in green chemistry metrics analysis.

A facile approach to spiro[dihydrofuran-2,3'-oxindoles] via formal [4 + 1] annulation reaction of fused 1H-pyrrole-2,3-diones with diazooxindoles.

There has been developed an easy synthetic approach to spiro[dihydrofuran-2,3'-oxindoles] via a highly diastereoselective formal [4 + 1] cycloaddition reaction of [e]-fused 1H-pyrrole-2,3-diones with diazooxindoles. The described novel heterocyclic systems are heteroanalogues of antimicrobial and antibiofilm fungal metabolites. The developed reaction represents the first example of involving 1H-pyrrole-2,3-diones fused at the [e]-side in a [4 + 1] annulation reaction.