Biological evaluation of polyhalo 1,3-diazaheterocycle fused isoquinolin-1(2H)-imine derivatives

Synthesis of Pyridin-2(1H)-imines via the Transformation of Conjugated Ynones

Conjugated ynones represent an important class of reactive species, useful synthetic intermediates, and synthons. However, the reactivity and synthetic applications of ynones are usually focused on the transformation of mono- or dual-functional groups. Herein, we developed a straightforward synthesis of pyridin-2(1H)-imines from the transformation of conjugated ynones. This cascade process probably began with a Michael addition of ynones and 2-aminopyridines, further underwent an intramolecular cyclization to generate the N,O-bidentate intermediates, and finally reacted with sulfonyl azides giving the pyridin-2(1H)-imines with accompanying loss of diazo.

Design, synthesis, in silico and biological evaluations of novel polysubstituted pyrroles as selective acetylcholinesterase inhibitors against Alzheimer's disease

The objective of this study was to design new polysubstituted pyrrole derivatives as selective acetylcholinesterase (AChE) inhibitors to target Alzheimer's disease. In this context, a highly efficient, one-pot, sequential, multi-component synthesis of a diverse range of polysubstituted pyrroles was developed through a sequential domino strategy by the condensation of amines with 1,1-bis(methylthio)-2-nitroethene (BMTNE), Knovenagle reaction of arylglyoxals with malono derivatives and subsequent Michael addition and intramolecular cyclization reaction in EtOH at reflux. Thirty-nine synthesized compounds were evaluated as AChE and butyrylcholinesterase (BChE) inhibitors. Among the synthesized compounds, compound 4ad (IC₅₀ = 2.95 ± 1.31 µM) was the most potent and selective AChE inhibitor with no significant inhibition against butyrylcholinesterase BChE. A kinetic study of 4ad revealed that this compound inhibited AChE in an uncompetitive mode. Based on a molecular modeling study, compound 4ad due to its small size properly fitted into the active site of AChE compared to BChE and stabilized by H-bond and hydrophobic interactions with the critical residues of the AChE binding pocket. Consequently, it was proposed that the 4ad derivative can be an ideal lead candidate against AD with a simple and practical operation of synthetic procedures.

Nitroenediamines (EDAMs), and N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) derivatives: scaffolds for heterocycle molecular diversity (update from 2012 to 2021)

This review highlights recent heterocyclization of the nitroenediamine derivatives based on catalyst and catalyst-free approaches from 2012 onwards.

An Environmentally Benign Cascade Reaction of 1,1-Enediamines (EDAMs) for Site-Selective Synthesis of Highly Functionalized 2,10-Dihydro-1H-imidazo[1',2':1,6]pyrido[2,3-b]indoles and Pyrroles

A novel protocol for the synthesis of pyrido[2,3-b]indoles (α-carbolines, 3) from (E)-3-(2-oxo-2-phenylethylidene) indolin-2-one derivatives 1 and 1,1-enediamine (EDAM) 2a via an unexpected cascade reaction in ethanol was developed. Pyrido[2,3-b]indole derivatives 4 were obtained by the same reaction, albeit by stirring the mixture for a longer period of time (about 48 h). As a result, two kinds of functionalized α-carbolines 3 and 4 were synthesized by the facile reaction of the (E)-3-(2-oxo-2-phenylethylidene)indolin-2-one derivatives and 2-(nitromethylene)imidazolidine under basic conditions (Cs₂CO₃) in ethanol. In addition, a diverse array of EDAM substrates (2b-2k) were tested in this reaction to afford the expected target compounds 5. This protocol is suitable for the combinatorial and parallel syntheses of natural-like products, including highly functionalized α-carbolines and pyrroles, especially 2-oxoindolin-3-yl pyrroles. This approach features several advantages, such as being a simple and practical operation (requiring only filtration and washing without column chromatography), furnishing excellent yields (72-98%), and producing diverse libraries of target compounds with potential biological activities.

Silver-catalyzed cascade reactions of 3-cyanochromone with 1,1-enediamines: synthesis of highly functionalized 2-(pyridin-3-yl)-chromeno[2,3-d]pyrimidines

A novel protocol for the construction of 2-(pyridin-3-yl)-chromeno[2,3-d]pyrimidines from 3-cyanochromone with 1,1-enediamines via an unprecedented cascade reaction has been developed by simply refluxing the reactants under the catalysis of silver carbonate.

Multicomponent Cascade Reaction by Metal-Free Aerobic Oxidation for Synthesis of Highly Functionalized 2-Amino-4-coumarinyl-5-arylpyrroles

A novel approach has been constructed for the synthesis of two types of 2-amino-4-coumarinyl-5-arylpyrroles (ACAPs, 5 and 6) through a cascade reaction and a metal-free catalyzed aerobic oxidation reaction of arylglyoxal monohydrates 1, 1,1-enediamines (EDAMs) 2 and 3, and 4-hydroxy-2H-chromen-2-ones 4 via multicomponent reactions to produce the target compounds with good to excellent yields. Specifically, hydroxyl-substituted 2-amino-4-coumarinyl-5-arylpyrroles, that is, 2-amino-4-coumarinyl-5-aryl-6-hydroxylpyrroles (ACAHPs) 6, were obtained by metal-free aerobic oxidation in 1,4-dioxane at simple reflux for approximately 10 h. As a result, ACAHPs 6 have been produced without metal catalysts or traditional oxidizing agents. This method represents a route to obtain the novel ACAPs in an environmentally friendly, concise, rapid, and practical manner with potential biological activity of the product.

Cascade Reaction of 1,1-Enediamines with 2-Benzylidene-1H-indene-1,3(2H)-diones: Selective Synthesis of Indenodihydropyridine and Indenopyridine Compounds

A concise and environmentally friendly route for the synthesis of diverse indenodihydropyridines (3) via a cascade reaction of 1,1-eneamines (1) with benzylidene-1H-indene-1,3(2H)-diones (BIDs) (2) in ethanol media was developed. The targeted compounds were efficiently obtained by only filtration without any further post-treatment. In the one-step cascade reaction, C-C and C-N bonds were constructed. In addition, when 1,4-dioxane was used as a solvent and the mixture of 1,1-eneamines (1) was refluxed with benzylidene-1H-indene-1,3(2H)-diones (BIDs) (2) for about 12 h, indenopyridine compounds (4) were produced. Two kinds of indenopyridine derivatives 3-4 resulted from alternative solvents and temperatures. The reaction had the following features: mild temperature, atom economy, high yields, and potential biological activity of the product.

Design, synthesis and biological evaluation of phosphopeptides as Polo-like kinase 1 Polo-box domain inhibitors

Polo-like kinase 1 (Plk1) is an anti-cancer target due to its critical role in mitotic progression. A growing body of evidence has documented that Peptide-Plk1 inhibitors showed high Plk1 binding affinity. However, phosphopeptides-Plk1 inhibitors showed poor cell membranes permeability, which limits their clinical applications. In current study, nine candidate phosphopeptides consisting of non-natural amino acids were rationally designed and then successfully synthesized using an Fmoc-solid phase peptide synthesis (SPPS) strategy. Moreover, the binding affinities and selectivity were evaluated via fluorescence polarization (FP) assay. The results confirmed that the most promising phosphopeptide 6 bound to Plk1 PBD with the IC50 of 38.99 nM, which was approximately 600-fold selectivity over Plk3 PBD (IC50 = 25.44 μM) and nearly no binding to Plk2 PBD. Furthermore the intracellular activities and the cell membrane permeability of phosphopeptide 6 were evalutated. Phosphopeptide 6 demonstrated appropriate cell membrane permeability and arrested HeLa cells cycle in G2/M phase by regulating CyclinB1-CDK1. Further, phosphopeptide 6 showed typical apoptotic morphology and induced caspase-dependent apoptosis. In conclusion, we expect our discovery can provide new insights into the further optimization of Plk1 PBD inhibitors.

Synthesis of Pyrimidopyrrolopyridazines via a Tandem Reaction of Heterocyclic Ketene Aminals with 1,2-Diaza-1,3-dienes

A tandem reaction of heterocyclic ketene aminals and 1,2-diaza-1,3-dienes was developed for the expedient synthesis of pyrimidopyrrolopyridazine derivatives. This process involved an intramolecular conjugate addition followed by CuCl₂-catalyzed hydrazone formation.

Phosphatase CDC25B Inhibitors Produced by Basic Alumina-Supported One-Pot Gram-Scale Synthesis of Fluorinated 2-Alkylthio-4-aminoquinazolines Using Microwave Irradiation

An efficient, environmentally benign, and inexpensive procedure has been developed for the synthesis of fluorinated 2-alkylthio-4-aminoquinazolines by microwave irradiation using basic alumina as a solid-support agent as well as a solid base. Notably, this protocol features improved energy efficiency, broad isothiourea substrate scope, easily available starting materials, and high atom efficiency and applicability toward gram-scale synthesis. Additionally, the target compounds were evaluated for the cytotoxic effect against human colon adenocarcinoma (HCT116 and HT29), human gastric cancer (SGC-7901), human lung adenocarcinoma (A549), and human hepatocyte carcinoma (HepG2) cells, and it was found that these compounds have excellent antitumor activities. Among them, compound 3e was found to be one of the most potent derivatives with IC₅₀ values lower than 9.44 μM against five human tumor cell lines, making it more active than cisplatin (DDP). Furthermore, for the first time, the fluorinated 2-alkylthio-substituted 4-aminoquinazolines were identified as phosphatase CDC25B inhibitors.

Facile Route to the Synthesis of 1,3-Diazahetero-Cycle-Fused [1,2-a]Quinoline Derivatives via Cascade Reactions

A one-step protocol without transition-metal catalysts with simple post-treatment for the synthesis of 1,3-diazaheterocycle-fused [1,2-a]quinoline derivatives via the cascade reaction of 2-fluorobenzaldehyde (1) and heterocyclic ketene aminals (2) was developed. In the one-step cascade reaction, C=C and C-N bonds were constructed, and the targeted compound can be efficiently obtained by filtering without column chromatography. This protocol describes a valuable route to concisely and feasibly obtain 1,3-diazaheterocycle-fused [1,2-a]quinoline derivatives. The synthetic methodology is particularly attractive because of the following features: low-cost solvent, mild temperature, atom economy, high yield, and potential biological activity of the product.

Diastereoselective Synthesis of Morphan Derivatives by Michael and Hetero-Michael Addition of 1,1-Enediamines to Quinone Monoketals

A general and concise method was developed for the synthesis of highly functionalized morphans 3-4 by the Michael and hetero-Michael addition reaction of different types of quinone monoketals 1 and 1,1-enediamines 2 in ethanol or 1,4-dioxane at reflux. This method is suitable for the efficient parallel syntheses of N-containing heterocycles. A library of highly functional morphan derivatives was easily constructed using the Michael/hetero-Michael reaction.

An Isoquinolin-1(2H)-Imine Derivative Induces Cell Death via Generation of Reactive Oxygen Species and Activation of JNK in Human A549 Cancer Cells

Compound 11-benzoyl-10-chloro-7,9-difluoro-6-imino-2,3,4,6-tetrahydro-1H-pyrimido[1,2-b]isoquinoline-8-carbonitrile (HC6h) is a novel polyhalo 1,3-diazaheterocycle fused isoquinolin-1(2H)-imines derivative, which displays good anticancer activity and low toxicity in vivo. However, the underlying anticancer mechanisms have not previously been identified. The proliferation of A549 was assessed by MTT assay. The reactive oxygen species (ROS) level was assessed in A549 with a H₂ DCFDA probe. Mitochondrial membrane potential was measured using the JC-1 staining. Apoptosis were measured by annexin-V/PI assay and autophagy by acridine orange staining and GFP-LC3 fluorescence assay. The expression of autophagic and apoptotic proteins was determined by Western blot. The compound HC6h increased accumulation of vesicles, acridine orange-stained cells and LC3-II in A549 cells. Inhibition of compound HC6h-induced autophagy by bafilomycin A1 increased apoptosis. Compound HC6h enhanced activation of caspase-3, caspase-9 and PARP cleavage in A549 cells. Compound HC6h leads to the rapid generation of intracellular ROS. Moreover, compound HC6h induced phosphorylation of JNK and was conferred by the increased ROS levels. Furthermore, down-regulation of JNK attenuated autophagic and apoptotic effect in response to HC6h. The induction of ROS upon HC6h treatment leads to the activation of JNK that mediates autophagy and apoptosis in human A549 cancer cells. J. Cell. Biochem. 118: 4394-4403, 2017. © 2017 Wiley Periodicals, Inc.

Synthesis of bicyclic 2-pyridones by regioselective annulations of heterocyclic ketene aminals with anhydrides

An efficient strategy for the synthesis of substituted bicyclic 2-pyridones is developed. The proposed approach is based on the regioselective N-acylation of heterocyclic ketene aminals (HKAs) with methacrylic anhydride or crotonic anhydride.

Regioselective synthesis of pyrrolo[1,2-a]imidazoles and imidazo[1,2-a]-pyridines

A concise synthesis of pyrrolo[1,2-a]imidazoles and imidazo[1,2-a]-pyridines by regioselective aza-ene additions and regioselective cyclic–condensation reactions of HKAs with ethyl 3-benzoylacrylate derivatives under catalyst-free conditions.

Synthesis and evaluation of the antitumor activity of polyhalo acridone derivatives

A series of polyhalo acridone heterocyclic compounds were synthesized and evaluated for theirin vitroantitumor activity. Compounds4d,4o,5jand5kshowed good antineoplastic selectivity.

Regioselective construction of 1,3-diazaheterocycle fused [1,2-a][1,8]naphthyridine derivatives via cascade reaction of quinolines with heterocyclic ketene aminals: a joint experimental-computational approach

A one-step, transition-metal-free protocol, involving facile post-treatment, for the regioselective synthesis of 1,3-diazaheterocycle fused [1,2-a][1,8]naphthyridine derivatives (3) from 2-chloroquinoline-3-carbaldehydes (ClQuAlds) (1) and heterocyclic ketene aminals (HKAs) (2) was developed via a joint experimental-computational approach. The computational prediction of the reactivity of two series of synthons was applied in the process of optimizing the reaction conditions, which relied on density functional theory (DFT) calculations together with concepts of frontier molecular orbital (FMO) theory and quantitative structure-reactivity relationship (QSRR) presumptions. The combined results enabled the proposal of a pre-synthetic prediction of global reactivity. The fully consistent results of the synthetic experiments with the in silico evaluation confirmed the rationality, effectiveness, and practicability of the new strategy. Notably, the joint method is not limited to the laboratory, but has applications ranging from routine to industry. This approach is likely to yield numerous insights to accelerate HKA-related synthetic chemistry that can be extended to numerous heterocycles. It thus opens up a novel entry towards rapidly investigating the reactivity of novel synthons with unique properties, a further step towards exploiting cascade reactions by avoiding the futile waste of time and resources.

Construction of C(sp2)–S and C(sp2)–Se bonds via a silver(i)-mediated coupling reaction of heterocyclic ketene aminals with diaryl dichalcogenides

A novel Ag(i)-mediated direct coupling reaction using HKAs and diaryl dichalcogenides for the construction of C(sp²)–chalcogenide bonds is reported. The transformation leads to a variety of α-arylthio and α-phenylselanyl HKAs with high regioselectivity and excellent yields.

Catalyst-free cascade reaction of heterocyclic ketene aminals with N-substituted maleimide to synthesise bicyclic pyrrolidinone derivatives

An efficient synthesis of bicyclic pyrrolidinones via a cascade reaction of HKAs and N-substituted maleimide in an environmentally friendly medium is described. This protocol uses group-assisted purification (GAP) chemistry. The library of bicyclic pyrrolidinone derivatives has been constructed with moderate to excellent yields.