A trypanocidal phenazine derived from beta-lapachone

Sodium sulfide-promoted regiodefined redox condensation of o-nitroanilines with aryl ketones to benzo[a]phenazines and quinoxalines

Inexpensive sodium sulfide trihydrate was found to promote unprecedented 6e-regio-predefined redox condensation of o-nitroanilines with α-tetralones to benzo[a]phenazines. The method was also successfully extended to acetophenones and higher homologs as reducing partners to provide 2-phenylquinoxalines. Compared to traditional approaches toward benzo[a]phenazine and quinoxaline cores starting with o-phenylenediamines, the present strategy could afford these heterocycles with well-defined regiochemistry based on the structure of starting o-nitroanilines.

Rh(III)-catalyzed oxidative [4+2] annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols

Synthesis of functionalized benzo[a]phenazines and indazolo[2,3-a]quinolines has been developed through Rh(III)-catalyzed oxidative annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols, respectively. The method features a broad substrate scope, excellent functional group tolerance, good to high yields of annulated products, and scaled-up synthesis capability. Based on a preliminary mechanistic investigation, a tentative mechanism of annulation reaction has been proposed.

A review on lawsone-based benzo[a]phenazin-5-ol: synthetic approaches and reactions

Phenazine systems are an important class of aza-polycyclic compounds that are easily found in nature and isolated as secondary metabolites primarily from Pseudomonas, Streptomyces, and a few other genera from soil or marine habitats. Moreover, various synthetic phenazine analogs are known for their pharmaceutical activities. Among various phenazines, benzo[a]phenazines are structural subunits in a variety of important natural products and have been given special attention due to their unique biological properties in various fields. In this review article, we highlight the synthesis of benzo[a]phenazin-5-ol derivatives from lawsone and benzene-1,2-diamines and their applications for the construction of a variety of five and six membered fused heterocycles such as pyranophenazines, spiropyranophenazines, pyridophenazines, furophenazines, benzochromenophenazines and oxazinophenazines during the period of 1995 to 2021.

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

Several low molecular weight naphthoquinones are very useful in organic synthesis. These compounds have given rise to thousands of other naphthoquinones that have been tested against various microorganisms and pharmacological targets, including being used in the preparation of several drugs that are on the pharmaceutical market. Among these naphthoquinones, the series of compounds prepared from 1,2-naphthoquinone-4-sulfonic acid salts (β-NQS) stands out. In addition to being used in organic synthesis, they are excellent analytical derivatization reagents to spectrophotometrically determine drugs containing primary and secondary amino groups. This review summarizes the literature involving β-NQS.

Naphthoquinones and Derivatives for Chemotherapy: Perspectives and Limitations of their Anti-trypanosomatids Activities

Chagas disease, Sleeping sickness and Leishmaniasis, caused by trypanosomatids Trypanosoma cruzi, Trypanosoma brucei and Leishmania spp., respectively, are considered neglected tropical diseases, and they especially affect impoverished populations in the developing world. The available chemotherapies are very limited, and a search for alternatives is still necessary. In folk medicine, natural naphthoquinones have been employed for the treatment of a great variety of illnesses, including parasitic infections. This review is focused on the anti-trypanosomatid activity and mechanistic analysis of naphthoquinones and derivatives. Among all the series of derivatives tested in vitro, naphthoquinone-derived 1,2,3-triazoles were very active on T. cruzi infective forms in blood bank conditions, as well as in amastigotes of Leishmania spp. naphthoquinones containing a CF₃ on a phenyl amine ring inhibited T. brucei proliferation in the nanomolar range, and naphthopterocarpanquinones stood out for their activity on a range of Leishmania species. Some of these compounds showed a promising selectivity index (SI) (30 to 1900), supporting further analysis in animal models. Indeed, high toxicity to the host and inactivation by blood components are crucial obstacles to be overcome to use naphthoquinones and/or their derivatives for chemotherapy. Multidisciplinary initiatives embracing medicinal chemistry, bioinformatics, biochemistry, and molecular and cellular biology need to be encouraged to allow the optimization of these compounds. Large scale automated tests are pivotal for the efficiency of the screening step, and subsequent evaluation of both the mechanism of action in vitro and pharmacokinetics in vivo is essential for the development of a novel, specific and safe derivative, minimizing adverse effects.

Biotin-phenosafranin as a new photosensitive conjugate for targeted therapy and imaging

A biotinylated phenazine compound as a phenosafranin conjugate (Biot-PSF) was synthesized and reported for the first time.

A comprehensive review on β-lapachone: Mechanisms, structural modifications, and therapeutic potentials

β-Lapachone (β-lap, 1), an ortho-naphthoquinone natural product isolated from the lapacho tree (Tabebuia avellanedae) in many regions of South America, has received extensive attention due to various pharmacological activities, such as antitumor, anti-Trypanosoma cruzi, anti-Mycobacterium tuberculosis, antibacterial, and antimalarial activities. Related mechanisms of β-lap have been widely investigated for a full understanding of its therapeutic potentials. Numerous derivatives of β-lap have been reported with aims to generate new chemical entities, improve the corresponding biological potency, and overcome disadvantages of its physical and chemical properties and safety profiles. This review will give insight into the pharmacological mechanisms of β-lap and provide a comprehensive understanding of its structural modifications with regard to different therapeutic potentials. The available clinical trials related to β-lap and its derivatives are also summarized.

One-Pot Synthesis of Spiro-isobenzofuran Compounds via the Sequential Condensation/Oxidation Reaction of Ninhydrin with 4-Amino-1,2-naphthoquinones/2-Amino-1,4-naphthoquinones under Mild Conditions

A one-pot route for the synthesis of spiro-isobenzofuran compounds was developed via the condensation reaction of ninhydrin with 4-amino-1,2-naphthoquinones or 2-amino-1,4-naphthoquinones in acetic acid followed by the oxidative cleavage of the corresponding vicinal diols at room temperature. Various derivatives of spiro[benzo[g]indole-2,1'-isobenzofuran]-3,3',4,5(1H) tetraones and spiro[benzo[f]pyrrolo[2,3-h]quinoxaline-2,1'-isobenzofuran]-3,3'(1H)-diones were synthesized in good to high yields. Moreover, further condensation of spiro[benzo[g]indole-2,1'-isobenzofuran]-3,3',4,5(1H)-tetraones with 1,2-diamines resulted in the new spiro-isobenzofuran compounds having phenazine rings in high yields.

Synthesis of 3-Amino-7-(N,N-Dimethylamino)-2-Substituted-5-Phenylphenazin-5-Ium Chlorides by Oxidative Cyclization

AIM AND OBJECTIVE

Phenazines are substances with an extensive range of important applications. Recently, the synthesis of N-arylation has been made more feasible owing to the advent of a new methodology. But because the toxicity of the used oxidant and the low yield, it is necessary to find a nonpoisonous or less toxic oxidant. We report on the use of potassium permanganate as an oxidant to synthesize phenylphenazin-5- ium chlorides via sequential aniline arylation.

MATERIALS AND METHODS

The corresponding 2-substituted-3-amino-5-phenyl-7-N,N-dimethylamino phenazinium chlorides were obtained via various o-substituted toluidines reacted with 4-amino-N,N-dimethyamine and aniline using potassium permanganate as an oxidant under different conditions such as temperature, pH, reaction time and the ratio of raw materials. Infrared (IR) absorption data were acquired on a Thermo Nicolet Nexus 670 FT-IR spectrometer with DTGS KBr detector. All the products were characterized by Mass, 1H and 13C NMR spectroscopy. The total C, H, N, content was measured by the elemental analyzer.

RESULTS

The yields of 3-amino-7-(N,N-dimethylamino)-2-substituted-5-phenylphenazin-5-ium chlorides are from 42.5% to 75.8% based on the electrophilic ability of different substituted groups under the temperature of 95°C, pH 4.5 and the reaction time of 8hrs.

CONCLUSION

3-Amino-7-(N,N-dimethylamino)-2-substituted-5-phenylphenazin-5-ium chlorides have been synthesized in high yields via the oxidative cyclization with potassium permanganate. This route is a simple, economic, efficient and environmentally friendly.

Two step, one-pot sequential synthesis of functionalized hybrid polyheterocyclic scaffolds via a solid state melt reaction (SSMR)

A new one pot assembly of highly functionalized benzo[a]phenazinone fused chromene/bicyclic scaffolds via a domino Knoevenagel intramolecular hetero-Diels-Alder (IMHDA) strategy using a solid state melt reaction (SSMR) of 2-hydroxynaphthalene 1,4-dione, o-phenylenediamine, O-allyl salicylaldehyde/O-vinyl salicylaldehyde derivatives is reported. The formation of five new bonds (two C-C bonds and three C-O bonds), three six-membered rings, and three stereogenic centers in a one-pot manner is very attractive. Ease of reaction with short time, good yields with water as the only byproduct and work up free procedure are some of the excellent features of the present protocol.

Synthesis of quinones with highlighted biological applications: A critical update on the strategies towards bioactive compounds with emphasis on lapachones

Naphthoquinones are of key importance in organic synthesis and medicinal chemistry. In the last few years, various synthetic routes have been developed to prepare bioactive compounds derived or based on lapachones. In this sense, this review is mainly focused on the synthetic aspects and strategies used for the design of these compounds on the basis of their biological activities for the development of drugs against the neglected diseases leishmaniases and Chagas disease and also cancer. Three strategies used to develop bioactive quinones are discussed and categorized: (i) C-ring modification, (ii) redox centre modification and (iii) A-ring modification. Framed within these strategies for the development of naphthoquinoidal compounds against T. cruzi. Leishmania and cancer, reactions including copper-catalyzed azide-alkyne cycloaddition (click chemistry), palladium-catalysed cross couplings, C-H activation reactions, Ullmann couplings and heterocyclisations reported up to July 2019 will be discussed. The aim of derivatisation is the generation of novel molecules that can potentially inhibit cellular organelles/processes, generate reactive oxygen species and increase lipophilicity to enhance penetration through the plasma membrane. Modified lapachones have emerged as promising prototypes for the development of drugs against leishmaniases, Chagas disease and cancer.

An efficient and environmentally sustainable domino protocol for the synthesis of structurally diverse spiroannulated pyrimidophenazines using erbium doped TiO2 nanoparticles as a recyclable and reusable heterogeneous acid catalyst

An efficient and environmentally sustainable domino protocol has been presented for the synthesis of structurally diverse spiroannulated pyrimidophenazines involving a four component reaction of 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamine, cyclic ketones and amino derivatives in the presence of erbium doped TiO2 nanoparticles as a recyclable and reusable heterogeneous acid catalyst. The present synthetic protocol features mild reaction conditions with operational simplicity, excellent yield with high purity, short reaction time and high atom economy with the use of a recoverable and reusable environmentally sustainable heterogeneous catalyst.

Cu-Catalyzed π-Core Evolution of Benzoxadiazoles with Diaryliodonium Salts for Regioselective Synthesis of Phenazine Scaffolds

The Cu-catalyzed regioselective synthesis of phenazine N-oxides was realized from benzoxadiazoles and diaryliodonium salts. The process was initiated by the electrophilic arylation of benzoxadiazoles with diaryliodonium salts and followed by benzocyclization reactions. The further reduction of N-oxides in situ to phenazine scaffolds and deviation to organic fluorescent materials were readily accomplished.

One-pot, sequential four-component synthesis of novel heterocyclic [3.3.3] propellane derivatives at room temperature

An efficient, one-pot, two-step, four-component reaction for the synthesis of propellane derivatives is described by the condensation reaction between acenaphthenequinone, malono derivatives, primary amines and β-ketoester or β-diketone derivatives in the presence of triethylamine in ethanol at room temperature. Using this procedure, all the products were obtained in good to excellent yields.

Regioselective 6-endo-dig iodocyclization: an accessible approach for iodo-benzo[a]phenazines

A facile approach for the synthesis of substituted iodo-benzo[a]phenazines from 2-aryl-3-(aryl/alkylethynyl)quinoxalines via 6-endo-dig ring closure has been described under mild reaction conditions. Iodocyclization proceeds through the iodonium ion intermediate followed by nucleophilic cyclization with the C-H bond of the arene. Furthermore, the resulting 6-iodo-5-aryl/alkyl benzo[a]phenazine derivatives allowed for structural diversification by employing various coupling reactions. The structure of iodo-benzo[a]phenazine was confirmed by X-ray crystallographic studies of the compound.

Cyclometalated ruthenium complexes from naturally occurring quinones: studies on their photophysical features, computational details and trypanocidal activity

Ligands and Ru(ii)-based complexes were synthesized from natural products and evaluated againstT. cruzi. These compounds could provide promising trypanocidal drugs.

Microwave-Assisted Synthesis of Bioactive Six-Membered Heterocycles and Their Fused Analogues

This review describes the formation of six-membered heterocyclic compounds and their fused analogues under microwave activation using modern organic transformations including cyclocondensation, cycloaddition, multicomponents and other modular reactions. The review is divided according to the main heterocycle types in order of increasing complexity, starting with heterocyclic systems containing one, two and three heteroatoms and their fused analogues. Recent microwave applications are reviewed, with special focus on the chemistry of bioactive compounds. Selected examples from the 2006 to 2015 literature are discussed.

Theophylline as the catalyst for the diastereoselective synthesis of trans-1,2-dihydrobenzo[a]furo[2,3-c]phenazines in water

Theophylline-catalyzed efficient and environmentally benign procedure for the diastereoselective synthesis of trans-1,2-dihydrobenzo[a]furo[2,3-c]phenazines with pyridinium ylide assisted domino reaction in water.

Epoxy-α-lapachone has in vitro and in vivo anti-leishmania (Leishmania) amazonensis effects and inhibits serine proteinase activity in this parasite

Leishmania (Leishmania) amazonensis is a protozoan that causes infections with a broad spectrum of clinical manifestations. The currently available chemotherapeutic treatments present many problems, such as several adverse side effects and the development of resistant strains. Natural compounds have been investigated as potential antileishmanial agents, and the effects of epoxy-α-lapachone on L. (L.) amazonensis were analyzed in the present study. This compound was able to cause measurable effects on promastigote and amastigote forms of the parasite, affecting plasma membrane organization and leading to death after 3 h of exposure. This compound also had an effect in experimentally infected BALB/c mice, causing reductions in paw lesions 6 weeks after treatment with 0.44 mM epoxy-α-lapachone (mean lesion area, 24.9 ± 2.0 mm(2)), compared to untreated animals (mean lesion area, 30.8 ± 2.6 mm(2)) or animals treated with Glucantime (mean lesion area, 28.3 ± 1.5 mm(2)). In addition, the effects of this compound on the serine proteinase activities of the parasite were evaluated. Serine proteinase-enriched fractions were extracted from both promastigotes and amastigotes and were shown to act on specific serine proteinase substrates and to be sensitive to classic serine proteinase inhibitors (phenylmethylsulfonyl fluoride, aprotinin, and antipain). These fractions were also affected by epoxy-α-lapachone. Furthermore, in silico simulations indicated that epoxy-α-lapachone can bind to oligopeptidase B (OPB) of L. (L.) amazonensis, a serine proteinase, in a manner similar to that of antipain, interacting with an S1 binding site. This evidence suggests that OPB may be a potential target for epoxy-α-lapachone and, as such, may be related to the compound's effects on the parasite.

Tetramethylguanidiniumchlorosulfonate ionic liquid (TMG IL): an efficient reusable catalyst for the synthesis of tetrahydro-1H-benzo[a]chromeno[2,3-c]phenazin-1-ones under solvent-free conditions and evaluation for their in vitro bioassay activity

The scope and versatility of multi-component reaction has been demonstrated in this methodology are highly reactive, potent activity, ecologically cleaner route and reusability.

Lawsone in organic synthesis

Lawsone has been used as the starting material for the synthesis of a variety of biologically active compounds and materials.