Three polymorphs of a new N,N'-dipropylated isoindigo derivative.

A newly synthesized N,N'-dipropyl-substituted isoindigo derivative, namely, 1-propyl-3-(1-propyl-1,2-dihydro-2-oxo-3H-indol-3-ylidene)-1,3-dihydro-2H-indol-2-one, C22H22N2O2, was found to have three polymorphic forms (denoted Forms I, II and III) under various crystallization conditions. Crystal structure analysis indicated that Form III had a significantly different molecular conformation from the other two polymorphs. Their different packing arrangements were correlated with differences in the intermolecular interactions. Thermal measurements revealed that Forms I and II are enantiotropically related, and Form II exhibits thermally dynamic behaviour.

(+)- and (-)-Tedanine, a pair of new enantiomeric indolone alkaloids from the marine sponge Tedania sp.

(+)- and (-)-Tedanine [(+)-1 and (-)-1], a pair of new enantiomeric indolone alkaloids, along with nine compounds (2-10) were isolated from the marine sponge Tedania sp. The structures of (+)-1 and (-)-1 including absolute configurations were determined by spectroscopic analysis and quantum chemical calculation. Compounds (+)-1 and (-)-1 were the first examples of indolone alkaloids isolated from this genus. In addition, the cytotoxic and antibacterial activities of these compounds were also evaluated.

Nitrene C-H Bond Insertion Approach to Carbazolones and Indolones, and a Reactivity Departure for 7-Membered Analogues.

A modular platform for facile access to 1,2,3,9-tetrahydro-4H-carbazol-4-ones (H4 -carbazolones) and 3,4-dihydrocyclopenta[b]indol-1(2H)-ones (H2 -indolones) is described. The requisite 6- and 5-membered 2-arylcycloalkane-1,3-dione precursors were readily obtained through a Cu-catalyzed arylation of 1,3-cyclohexanediones or by a ring expansion of aryl succinoin derivatives. Enolization of one carbonyl group in the diones, conversion to a leaving group, and subsequent azidation gave 2-aryl-3-azidocycloalk-2-en-1-ones. This two-step, one-pot azidation is highly regioselective with unsymmetrically substituted 2-arylcyclohexane-1,3-diones. The regioselectivity, which is important for access to single isomers of 3,3-disubstituted carbazolones, was analyzed mechanistically and computationally. Finally, a Rh-catalyzed nitrene/nitrenoid insertion into the ortho C-H bond of the aryl moiety gave the H4 -carbazolones and H2 -indolones. One carbazolone was elaborated to an intermediate reported in the total synthesis of N-decarbomethoxychanofruticosinate, (-)-aspidospermidine, (+)-kopsihainanine A. With 2-phenylcycloheptane-1,3-dione, prepared from cyclohexanone and benzaldehyde, the azidation reaction was readily accomplished. However, the Rh-catalyzed reaction unexpectedly led to a labile but characterizable azirine rather than the indole derivative. Computations were performed to understand the differences in reactivities of the 5- and 6-membered 2-aryl-3-azidocycloalk-2-en-1-ones in comparison to the 7-membered analogue, and to support the structural assignment of the azirine.

Design, synthesis, and biological evaluation of a series of indolone derivatives as novel FLT3 inhibitors for the treatment of acute myeloid leukemia.

FLT3-ITD mutant has been extensively studied as a drug discovery target for acute myeloid leukemia. Based on our previous discovered FLT3 inhibitor (2), a series of urea group based indolone derivatives were designed, synthesized, and biological evaluated as novel FLT3 inhibitors for the treatment of FLT3-ITD positive AML. Among them, compound LC-3 exhibited potent inhibitory effects against FLT3 (IC50 = 8.4 nM) and significantly inhibited the proliferation of FLT3-ITD positive AML cells MV-4-11 (IC50 = 5.3 nM). In the cellular context, LC-3 strongly inhibited FLT3-mediated signaling pathways and induced cellular apoptosis by arresting cell cycle in G1 phase. In the in vivo studies, LC-3 significantly suppressed the tumor growth on MV-4-11 xenograft models (10 mg/kg/day, TGI = 92.16%) without exhibiting obvious toxicity. These results suggested that compound LC-3 might be a potential drug candidate for FLT3-ITD positive AML.

Thiazolyl hydrazineylidenyl indolones as unique potential multitargeting broad-spectrum antimicrobial agents.

The emergence of pathogenic and drug-resistant microorganisms seriously threatens public safety. This work constructed a unique type of thiazolyl hydrazineylidenyl indolones (THIs) to combat global microbial multidrug-resistance. Bioactive evaluation discovered that some target THIs displayed much superior antimicrobial efficacy than clinical chloromycetin, norfloxacin, cefdinir or fluconazole against the tested strains. Eminently, butyl THI 6c displayed a broad antimicrobial spectrum with low MICs of 0.25-1 µg/mL. The highly active THI 6c not only showed low cytotoxicity and hemolysis, rapidly bactericidal ability, good antibiofilm activity and promising pharmacokinetic properties, but also could significantly impede the development of bacterial resistance. Preliminary exploration of antibacterial mechanism revealed that THI 6c could effectively penetrate the cell membrane of MRSA and embed DNA to form 6c‒DNA supramolecular complex and thus hinder DNA replication. Moreover, THI 6c could reduce cell metabolic activity, which might be attributed to the fact that THI 6c could target the pyruvate kinase of MRSA and interfere with the function of the enzyme. These results provided powerful information for further developing thiazolyl hydrazineylidenyl indolones as new broad-spectrum antimicrobial agents.

Synthesis and Biological Evaluation of Novel Synthetic Indolone Derivatives as Anti-Tumor Agents Targeting p53-MDM2 and p53-MDMX.

A series of novel indolone derivatives were synthesized and evaluated for their binding affinities toward MDM2 and MDMX. Some compounds showed potent MDM2 and moderate MDMX activities. Among them, compound A13 exhibited the most potent affinity toward MDM2 and MDMX, with a Ki of 0.031 and 7.24 µM, respectively. A13 was also the most potent agent against HCT116, MCF7, and A549, with IC50 values of 6.17, 11.21, and 12.49 µM, respectively. Western blot analysis confirmed that A13 upregulated the expression of MDM2, MDMX, and p53 by Western blot analysis. These results indicate that A13 is a potent dual p53-MDM2 and p53-MDMX inhibitor and deserves further investigation.

4,5,6,7-Tetrahydroindol-4-Ones as a Valuable Starting Point for the Synthesis of Polyheterocyclic Structures.

This review focuses on the synthesis of polyheterocyclic structures with a variety of medicinal and optoelectronic applications, starting from readily available 4,5,6,7-tetrahydroindol-4-one analogs. First, routes toward the 4,5,6,7-tetrahydroindol-4-one starting materials are summarized, followed by synthetic pathways towards polyheterocyclic structures which are categorized based on the size and attachment point of the newly formed (hetero)cyclic ring.

Design and Synthesis of Pyrano[3,2-b]indolones Showing Antimycobacterial Activity.

Latent Mycobacterium tuberculosis infection presents one of the largest challenges for tuberculosis control and novel antimycobacterial drug development. A series of pyrano[3,2-b]indolone-based compounds was designed and synthesized via an original eight-step scheme. The synthesized compounds were evaluated for their in vitro activity against M. tuberculosis strains H37Rv and streptomycin-starved 18b (SS18b), representing models for replicating and nonreplicating mycobacteria, respectively. Compound 10a exhibited good activity with MIC99 values of 0.3 and 0.4 µg/mL against H37Rv and SS18b, respectively, as well as low toxicity, acceptable intracellular activity, and satisfactory metabolic stability and was selected as the lead compound for further studies. An analysis of 10a-resistant M. bovis mutants disclosed a cross-resistance with pretomanid and altered relative amounts of different forms of cofactor F420 in these strains. Complementation experiments showed that F420-dependent glucose-6-phosphate dehydrogenase and the synthesis of mature F420 were important for 10a activity. Overall these studies revealed 10a to be a prodrug that is activated by an unknown F420-dependent enzyme in mycobacteria.

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor.

A convergent strategy is reported for the construction of nitrogen-containing heterocycles from common substrates: 1,4-diketones and primary amines. Indeed, by just varying the substrates, the substituents, or the heating mode, it is possible to selectively synthesize indole, indolone (1,5,6,7-tetrahydroindol-4-one), or cinnoline (5,6,7,8-tetrahydrocinnoline) derivatives in moderate to excellent yields.

Integrating Molecular Network and Culture Media Variation to Explore the Production of Bioactive Metabolites by Vibrio diabolicus A1SM3.

Vibrio diabolicus A1SM3 strain was isolated from a sediment sample from Manaure Solar Saltern in La Guajira and the produced crude extracts have shown antibacterial activity against methicillin-resistant Staphylococcus aureus and cytotoxic activity against human lung cell line. Thus, the aim of this research was to identify the main compound responsible for the biological activity observed and to systematically study how each carbon and nitrogen source in the growth media, and variation of the salinity, affect its production. For the characterization of the bioactive metabolites, 15 fractions obtained from Vibrio diabolicus A1SM3 crude extract were analyzed by HPLC-MS/MS and their activity was established. The bioactive fractions were dereplicated with Antibase and Marinlit databases, which combined with nuclear magnetic resonance (NMR) spectra and fragmentation by MS/MS, led to the identification of 2,2-di(3-indolyl)-3-indolone (isotrisindoline), an indole-derivative antibiotic, previously isolated from marine organisms. The influence of the variations of the culture media in isotrisindoline production was established by molecular network and MZmine showing that the media containing starch and peptone at 7% NaCl was the best culture media to produce it. Also, polyhydroxybutyrates (PHB) identification was established by MS/MS mainly in casamino acids media, contributing to the first report on PHB production by this strain.

Dual inhibitors of RAF-MEK-ERK and PI3K-PDK1-AKT pathways: Design, synthesis and preliminary anticancer activity studies of 3-substituted-5-(phenylamino) indolone derivatives.

The dysfunction and mutual compensatory activation of RAF-MEK-ERK and PI3K-PDK1-AKT pathways have been demonstrated as the hallmarks in several primary and recurrent cancers. The strategy of concurrent blocking of these two pathways shows clinical merits on effective cancer therapy, such as combinatory treatments and dual-pathway inhibitors. Herein, we report a novel prototype of dual-pathway inhibitors by means of merging the core structural scaffolds of a MEK1 inhibitor and a PDK1 inhibitor. A library of 43 compounds that categorized into three series (Series I-III) was synthesized and tested for antitumor activity in lung cancer cells. The results from structure-activity relationship (SAR) analysis showed the following order of antitumor activity that 3-hydroxy-5-(phenylamino) indolone (Series III) > 3-alkenyl-5-(phenylamino) indolone (Series I) > 3-alkyl-5-(phenylamino) indolone (Series II). A lead compound 9za in Series III showed most potent antitumor activity with IC50 value of 1.8 ±â€¯0.8 µM in A549 cells. Moreover, antitumor mechanism study demonstrated that 9za exerted significant apoptotic effect, and cellular signal pathway analysis revealed the potent blockage of phosphorylation levels of ERK and AKT in RAF-MEK-ERK and PI3K-PDK1-AKT pathways, respectively. The results reported here provide robust experimental basis for the discovery and optimization of dual pathway agents for anti-lung cancer therapy.

Manganese(I)-Catalyzed C-H Activation/Diels-Alder/retro-Diels-Alder Domino Alkyne Annulation featuring Transformable Pyridines.

Complexity-increasing Domino reactions comprising C-H allenylation, a Diels-Alder reaction, and a retro-Diels-Alder reaction were realized by a versatile catalyst derived from earth-abundant, non-toxic manganese. The C-H activation/Diels-Alder/retro-Diels-Alder alkyne annulation sequence provided step-economical access to valuable indolone alkaloid derivatives through a facile organometallic C-H activation manifold with transformable pyridines.

2-Aryl-3H-indol-3-ones: synthesis, electrochemical behaviour and antiplasmodial activities.

The synthesis of indolone derivatives and their antiplasmodial activity in vitro against Plasmodium falciparum at the blood stage are described. The 2-aryl-3H-indol-3-ones were synthesized via deoxygenation of indolone-N-oxides. Electrochemical behaviour, antiplasmodial activity and cytotoxicity on human tumor cell lines were compared to those of indolone-N-oxides. The antiplasmodial IC50 (concentrations at 50% inhibition) of these compounds ranged between 49 and 1327 nM. Among them, the 2-(4-dimethylaminophenyl)-5-methoxy-indol-3-one, 7, had the best antiplasmodial activity in vitro (IC50 = 49 nM; FcB1 strain) and selectivity index (SI (CC50 MCF7/IC50 FcB1) = 423.4). Thus, the hits identified in this deoxygenated series correspond to their structural homologs in the N-oxide series with comparable electrochemical behaviour at the nitrogen-carbon double bond.

Amino derivatives of indolone-N-oxide: preparation and antiplasmodial properties.

There is an urgent need for new antimalarial drugs with novel mechanisms of action on novel targets. Indolone-N-oxides (INODs) display antimalarial properties in vitro and in vivo, but identified leads such as 6-(4-chloro-phenyl)-5-oxy-[1,3]dioxolo[4,5-f]indol-7-one 1, suffer from very poor aqueous solubility. In this study, structural modifications have been made by introducing various amino and bulky groups to produce sufficiently water soluble and active compounds for further pharmacological and pharmacokinetic studies. We report here the preparation of twelve novel amino derivatives and their antiplasmodial activities including those of two other structurally known compounds. The 5-methoxy-2-(4-morpholin-4-yl-phenyl)-1-oxy-indol-3-one, 9, has the highest antiplasmodial activity in vitro (IC50 = 6.5 nM; FcB1 strain) and selectivity index (SI (CC50 MCF7/IC50 FcB1) = 4538.5). The 6-amino-2-(4-chloro-phenyl)-1-oxy-indol-3-one, 14, (IC50 = 183 nM; SI = 60), is an excellent candidate for further mechanistic studies. Indeed, this is structurally the closest analogue to the current lead, 1, bearing an NH2 group at R(2) offering possibilities for functionalization and labeling.

Albumin-bound nanoparticles of practically water-insoluble antimalarial lead greatly enhance its efficacy.

We recently showed that the indolone-N-oxides can be promising candidates for the treatment of chloroquine-resistant malaria. However, the in vivo assays have been hampered by the very poor aqueous solubility of these compounds resulting in poor and variable activity. Here, we describe the preparation, characterization and in vivo evaluation of biodegradable albumin-bound indolone-N-oxide nanoparticles. Nanoparticles were prepared by precipitation followed by high-pressure homogenization and characterized by photon correlation spectroscopy, transmission electron microscopy, differential scanning calorimetry and X-ray powder diffraction. The process was optimized to yield nanoparticles of controllable diameter with narrow size distribution suitable for intravenous administration, which guarantees direct drug contact with parasitized erythrocytes. Stable nanoparticles showed greatly enhanced dissolution rate (complete drug release within 30 min compared to 1.5% of pure drug) preserving the rapid antimalarial activity. The formulation achieved complete cure of Plasmodium berghei-infected mice at 25mg/kg with parasitemia inhibition (99.1%) comparable to that of artesunate and chloroquine and was remarkably more effective in prolonging survival time and inhibiting recrudescence. In 'humanized' mice infected with Plasmodium falciparum, the same dose proved to be highly effective: with parasitemia reduced by 97.5% and the mean survival time prolonged. This formulation can help advance the preclinical trials of indolone-N-oxides. Albumin-bound nanoparticles represent a new strategic approach to use this most abundant plasma protein to target malaria-infected erythrocytes.

Pro-oxidant properties of indolone-N-oxides in relation to their antimalarial properties.

Indolone-N-oxides (INODs) are bioreducible and possess remarkable anti-malarial activities in the low nanomolar range in vitro against different Plasmodium falciparum (P. falciparum) strains and in vivo. INODs have an original mechanism of action: they damage the host cell membrane without affecting non-parasitized erythrocytes. These molecules produce a redox signal which activates SYK tyrosine kinases and induces a hyperphosphorylation of AE1 (band 3, erythrocyte membrane protein). The present work aimed to understand the early stages of the biochemical interactions of these compounds with some erythrocyte components from which the redox signal could originate. The interactions were studied in a biomimetic model and compared with those of chloroquine and artemisinin. The results showed that INODs i) do not enter the coordination sphere of the metal in the heme iron complex as does chloroquine; ii) do not generate iron-dependent radicals as does artemisinin; iii) generate stable free radical adducts after reduction at one electron; iv) cannot trap free radicals after reduction. These results confirm that the bioactivity of INODs does not lie in their spin-trapping properties but rather in their pro-oxidant character. This property may be the initiator of the redox signal which activates SYK tyrosine kinases.