Structural insights of oxindole based kinase inhibitors as anticancer agents: Recent advances

Small-molecule kinase inhibitors are being continuously explored as new anticancer therapeutics. Kinases are the phosphorylating enzymes which regulate numerous cellular functions such as proliferation, differentiation, migration, metabolism, and angiogenesis by activating several signalling pathways. Kinases have also been frequently found to be deregulated and overexpressed in cancerous tissues. Therefore, modulating the kinase activity by employing small molecules has emerged as a strategic approach for cancer treatment. On the other hand, oxindole motifs have surfaced as privileged scaffolds with significant multi-kinase inhibitory activity. The present review summarises recent advances in the development of oxindole based kinase inhibitors. The role of distinguished structural frameworks of oxindoles, such as 3-alkenyl oxindoles, spirooxindoles, 3-iminooxindoles and similar hydrazone derivatives have been described based on their kinase inhibition potential. Furthermore, the design strategies, mechanism of actions, structure activity relationships (SARs) and their mode of interaction with target protein have been critically highlighted.

Ring-opening cyclization of activated spiro-aziridine oxindoles with heteroarenes: a facile synthetic approach to spiro-oxindole-fused pyrroloindolines

Herein, we report a facile tandem approach for the synthesis of both spiro-oxindole-fused pyrroloindolines and benzofurano-pyrrolidines via a Lewis acid-catalyzed domino ring-opening with concomitant ring annulation using activated spiro-aziridines and heteroarenes. This method offers a new class of novel spiro-fused polycyclic pyrrolidines in a one-pot and sustainable manner with good yields and high diastereoselectivity. In addition, the structure of 3d was confirmed by single X-ray crystallography analysis.

Syntheses and reactivity of spiro-epoxy/aziridine oxindole cores: developments in the past decade

This review highlights various reactions to afford spiro-epoxy/aziridine oxindoles and their potential synthetic transformations.

Iodine-mediated C-N and N-N bond formation: a facile one-pot synthetic approach to 1,2,3-triazoles under metal-free and azide-free conditions

A novel strategy towards the synthesis of 1,4-disubstituted 1,2,3-triazoles via C–N and N–N bond formation has been demonstrated under transition metal-free and azide-free conditions. These 1,2,3-triazoles were obtained in a regioselective manner from commercially available anilines, aryl alkenes/aryl alkynes and N-tosylhydrazines using I₂ under O₂ atmosphere. Broad substrate scope, milder reaction conditions, good to moderate yields and clean protocol are the notable features of the method. Moreover, this protocol is amenable for the generation of a library of medicinally important key building blocks.

A novel strategy towards the synthesis of 1,4-disubstituted 1,2,3-triazoles via C–N and N–N bond formation has been demonstrated under transition metal-free and azide-free conditions.

Controlling the regioselectivity of the ring opening of spiro-epoxyoxindoles for efficient synthesis of C(3)–N(1′)-bisindoles and C(3)–N(1′)-diindolylmethane

A strategy for the construction of both C(3)–N(1′) bisindoles and C(3)–N(1′) diindolylmethane has been explored via tuning of the nucleophilicity of indoline/indole to spiro-epoxyoxindole.

Synthesis of enamino-2-oxindoles via conjugate addition between α-azido ketones and 3-alkenyl oxindoles: Cytotoxicity evaluation and apoptosis inducing studies

A facile method for the construction of double bond between 3-ylidene oxindoles and α-azido ketones has been successfully accomplished with a mild base. This method features azido reduction with concomitant double bond formation to provide the new class of bioactive enamino-2-oxindoles. These new compounds were screened for their in vitro cytotoxic potential on selected human cancer cell lines such as colon, lung, breast, and cervical cancer cells. Among them, representative compounds 3a, 3h, 3k, 3p, 3w and 3x showed notable cytotoxicity profile with IC₅₀ values ranging from 1.40 ± 0.10 to 28.7 ± 0.36 µM. Compound 3k displayed most potent cytotoxicity against lung cancer (NCI-H460) cells with an IC₅₀ value of 1.40 ± 0.10 µM. 3k also arrested the G2/M phase of the cell cycle and induced distinctive apoptotic features on lung cancer cells. The apoptosis induction is supported by various cellular assays such as AO/EB, DAPI, and DCFDA staining studies including clonogenic assay. Extent of apoptosis was also analyzed by Annexin binding and JC-1 staining. Moreover, this method is amenable for the generation of a library of new class of stable bioactive enamino-2-oxindoles.

Green click synthesis of β-hydroxy-1,2,3-triazoles in water in the presence of a Cu(ii)–azide catalyst: a new function for Cu(ii)–azide complexes

A new method for preparing 1,2,3-triazols via a [3+2]-cycloaddition reaction is introduced. The effect of reaction temperature on the epoxide ring opening reactions is also investigated.

Silver(i)-catalysed domino alkyne-annulation/Diels–Alder reaction: a mild synthetic approach to tetrahydrospiro[carbazole-4,3′-indoline] scaffolds

A mild and efficient AgOTf catalyzed alkyne-annulation/Diels–Alder cascade for the construction of tetrahydrospiro[carbazole-4,3′-indoline] derivatives has been established.

A recyclable and water soluble copper(i)-catalyst: one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles and their biological evaluation

A protocol for the synthesis of 1,4-disubstituted 1,2,3-triazoles via three-component reaction by a water soluble copper(i) complex has been developed.

Cu–Al mixed oxide catalysts for azide–alkyne 1,3-cycloaddition in ethanol–water

Cu(Al)O mixed oxide promotes the formation of 1,2,3-triazoles from an alkyne–azide cycloaddition reaction with excellent yields using an EtOH–H₂O mixture as the solvent under microwave heating.

CsOH/γ-Al2O3: a heterogeneous reusable basic catalyst for one-pot synthesis of 2-amino-4,6-diaryl pyrimidines

Pyrimidine derivatives were synthesized in one pot using a novel heterogeneous reusable catalyst, and complete characterization of catalyst was performed.

A stereolibrary of conformationally restricted amino acids based on pyrrolidinyl/piperidinyloxazole motifs

A stereolibrary of conformationally restricted oxazole-containing amino acids, namely all isomers of 5–pyrrolydinyl- and 5-piperidinyloxazole-4-carboxylic acids, were designed and synthesized in three steps by the reaction of the corresponding N-Boc-protected amino acids and ethyl isocyanoacetate. These natural products-inspired amino acids are valuable building blocks for the synthesis of peptidomimetics and potential lead compounds for drug discovery.

Spirooxindole-derived morpholine-fused-1,2,3-triazoles: Design, synthesis, cytotoxicity and apoptosis inducing studies

A series of new spirooxindole-derived morpholine-fused-1,2,3-triazole derivatives has been synthesized from isatin spiro-epoxides. The protocol involves regiospecific isatin-epoxide ring opening with azide nucleophile followed by sequential O-propargylation, and intramolecular 1,3-dipolar cycloaddition reaction. These compounds have been evaluated for their antiproliferative activity against selected human tumor cell lines of lung (A549), breast (MCF-7), cervical (HeLa), and prostate (DU-145). Among the tested compounds, 6i, 6n and 6p showed potent growth inhibition against A549 cell line with IC50 values in the range of 1.87-4.36 μM, which are comparable to reference standards doxorubicin and 5-flourouracil. The compounds 6i and 6p treated A549 cells displayed typical apoptotic morphological features such as cell shrinkage, nuclear condensation, fragmentation, and decreased migration potential. Flow-cytometry analysis revealed that the compounds arrested the cells in G2/M phase of cell cycle. Hoechst and acridine orange/ethidium bromide staining studies also showed that the cell proliferation was inhibited through induction of apoptosis. Moreover, the compounds treatment led to collapse of the mitochondrial membrane potential (DΨm) and increased levels of reactive oxygen species (ROS) were noted in A549 cells.