Luotonin A. A Naturally Occurring Human DNA Topoisomerase I Poison

Discovery of Indolo[3,2-c]isoquinoline Derivatives as Novel Top1/2 Dual Inhibitors with Orally Efficacious Antitumor Activity and Low Toxicity

Topoisomerase (Top) inhibitors used in clinical cancer treatments are limited because of their toxicity and severe side effects. Noteworthily, Top1/2 dual inhibitors overcome the compensatory effect between Top1 and 2 inhibitors to exhibit stronger antitumor efficacies. In this study, a series of indolo[3,2-c]isoquinoline derivatives were designed as Top1/2 dual inhibitors possessing apparent antiproliferative activities. Mechanistic studies indicated that the optimal compounds 23 and 31 with increasing reactive oxygen species levels damage DNA, inducing both cancer cell apoptosis and cycle arrest. Importantly, the results of the toxicity studies showed that compounds 23 and 31 possessed good oral safety profiles. In xenograft models, compound 23 exhibited remarkable antitumor potency, which was superior to the clinical Top inhibitors irinotecan and etoposide. Overall, this work highlights the therapeutic potential and safety profile of compound 23 as a Top1/2 dual inhibitor in tumor therapy and provides valuable lead compounds for further development of Top inhibitors.

Synthesis of N-Alkyl Substituted Benzimidazoquinazolinones

Aromatic N-heterocycles, especially benzimidazoquinazolinones featuring alkyl chains, hold significant pharmaceutical relevance. Here, we introduce a streamlined one-pot, 2-fold Cu-catalyzed C-N bond formation protocol for the efficient synthesis of diverse N-alkyl benzimidazoquinazolinone derivatives. This method showcases a broad substrate scope, leveraging readily accessible alkyl halides and delivers the desired cyclized products in excellent yields. Additionally, the methodology enabled the synthesis of an antitumor agent with satisfactory yield, highlighting its utility in medicinal chemistry endeavors.

Recent Advances in the Research on Luotonins A, B, and E

This digest review summarises the most recent progress in the study on luotonins A, B and E. The literature covered in this overview spans from January 2012 to April 2024 and presents synthetic methodologies for the assembly of the quinolinopyrrolo-quinazoline scaffold, the structural motifs present in luotonins A, B, and E, and the evaluation of the biological activities of their derivatives and structural analogues.

Tf2O-mediated [4+2]-annulation of anthranils with 2-chloropyridines: enabling access to pyridoquinazolinones and euxylophoricine B

We present an efficient approach for synthesizing pyridoquinazolinones in the presence of triflic anhydride utilizing anthranils and 2-chloropyridines as starting materials. In this process, Tf2O initially activates anthranils forming an electrophilic 1-((trifluoromethyl)sulfonyl)benzo[c]isoxazol-1-ium species. This species undergoes an in situ annulation reaction with 2-chloropyridines, resulting in therapeutically useful pyridoquinazolinones. The reaction is tolerant to various functional groups, allowing access to a wide range of substituted pyridoquinazolinones in good yields. Furthermore, the synthesis of euxylophoricine B, known to be an antitumor agent, was also achieved.

Synthesis of quinazolinone scaffolds via a zinc(II)-stabilized amidyl radical-promoted deaminative approach

Herein, we report a solely ligand centered redox controlled protocol, utilizing a bench stable zinc compound, for the efficient coupling of o-amino amides/esters with nitriles to afford diverse quinazolinone scaffolds and their synthetic utility was showcased via post-modification to access therapeutically relevant compounds. Importantly, mechanistic probes established the reaction pathway that proceeds via aminyl radical.

Synthesis of Pyrimido[1,2-a]indolediones and Pyrimidinediones via [4+2] Annulation of 2H-Azirine-2-carbaldehydes

NHC-catalyzed [4+2] annulation of 2H-azirine-2-carbaldehydes with ketimines and isocyanates has been developed, providing straightforward synthetic protocols for constructing structurally intriguing pyrimido[1,2-a]indolediones and pyrimidinediones under mild conditions with excellent yields. This protocol can be used to synthesize the core skeleton of pharmaceutically important drugs and pyrimido[1,2-a]indoledione-containing natural products, making it potentially valuable for creating biologically active derivatives.

Biological properties of pyrroloquinoline and pyrroloisoquinoline derivatives

In this review, we summarize pyrroloquinoline and pyrroloisoquinoline derivatives (PQs and PIQs) that act on a broad spectrum of biological targets and are used as bacteriostatic, antiviral, plasmodial, anticancer, antidiabetic and anticoagulant agents. Many of these compounds play important roles in the study of DNA and its interactions, the regulation of the cell cycle and programmed cell death. This review involves twenty-five types of skeletally analogical compounds bearing pyrrole and (iso)quinoline scaffolds with different mutual annelations.

Photocatalytic cyclization of 3-(2-isocyanophenyl)quinazolin-4(3H)-ones for the construction of quinoxalino[2,1-b]quinazolinones

A new kind of building unit, 3-(2-isocyanophenyl)quinazolin-4(3H)-ones, was designed and synthesized for the construction of novel quinoxalino[2,1-b]quinazolinones. The radical cyclization of 3-(2-isocyanophenyl)quinazolin-4(3H)-ones with ethers afforded ether-substituted tetracyclic quinoxalino[2,1-b]quinazolinones under photocatalytic and metal-free conditions. In the process, the isocyano accepts a carbon radical to give an imidoyl radical, which adds to the electron-deficient CN bond in quinazolin-4(3H)-one.

Natural products fragment-based design and synthesis of a novel pentacyclic ring system as potential MAPK inhibitor

The synthesis of compounds based on fragments derived from natural products (NPs) serves as a source of inspiration for the design of pseudo-natural products (PNPs), to identify bioactive molecules that exhibit similar characteristics to NPs. These novel molecular scaffolds exhibit previously unexplored biological activities as well. This study reports the development and synthesis of a novel pentacyclic ring system, the indole-pyrimidine-quinoline (IPQ) scaffold. The design of this scaffold was based on the structural characteristics of four natural products, namely tryptanthrin, luotonin A, rutaecarpine, and camptothecin. Several successive steps accomplished the effective synthesis of the IPQ scaffold. The constituent components of the pentacycle, containing the indole, quinazolinone, pyrimidone, and quinoline units, possess significant biological significance. Compound 1a demonstrated noteworthy anti-tumor activity efficacy against A549 cell lines among the tested compounds. The compound 1a was observed to elicit cell cycle arrest in both the G2/M and S phases, as well as trigger apoptosis in A549 cells. These effects were attributed to its ability to modulate the activation of mitochondrial-related mitogen-activated protein kinase (MAPK) signaling pathways.

Cyclizations of Alkenyl(Alkynyl)-Functionalized Quinazolinones and their Heteroanalogues: A Powerful Strategy for the Construction of Polyheterocyclic Structures

Quinazolin-4-one, its heteroanalogues, and derivatives represent an outstandingly important class of compounds in modern organic, medicinal, and pharmaceutical chemistry, as these molecular structures are noted for their wide synthetic and pharmacological potential. In the last years, ever-increasing research attention has been paid to quinazolinone derivatives bearing alkenyl and alkynyl substituents on the pyrimidinone nucleus. The original structural combination of synthetically powerful endocyclic amidine (or amidine-related) and exocyclic unsaturated moieties provides a driving force for cyclizations, which offer an efficient toolkit to construct a variety of fused pyrimidine systems with saturated N- and N,S-heterocycles. In this connection, the present review article is mainly aimed at systematic coverage of the progress in using alkenyl(alkynyl)quinazolinones and their heteroanalogues as convenient bifunctional substrates for regioselective annulation of small- and medium-sized heterocyclic nuclei. Much attention is paid to elucidating the structural and electronic effects of reagents on the regio- and stereoselectivity of the cyclizations as well as to clarifying the relevant reaction mechanisms.

Nickel-Catalyzed Intramolecular Dual Annulation Reaction of Aryl Nitrile-Containing 1,2,3-Benzotriazin-4(3H)-ones: A Pathway To Synthesize Luotonin A and Related Polycyclic Pyrroloquinazolinones

Herein, we report a nickel-catalyzed intramolecular denitrogenative dual annulation reaction of aryl nitrile-containing 1,2,3-benzotriazine-4(3H)-ones to synthesize polycyclic pyrroloquinazolinones with a tolerance of a wide diversity of substituents. This catalytic reaction is the first denitrogenative transannulation of 1,2,3-benzotriazine-4(3H)-one with nitrile, which can be applied as the critical step to synthesize luotonin A with a high step economy.

H2O2-Mediated Synthesis of a Quinazolin-4(3H)-one Scaffold: A Sustainable Approach

A quinazolin-4(3H)-one ring system is a privileged heterocyclic moiety with distinctive biological properties. From this perspective, the development of an efficient strategy for the synthesis of quinazolin-4(3H)-one has always been in demand for the synthetic chemistry community. In this report, we envisaged an efficient protocol for the synthesis of quinazolin-4(3H)-one using substituted 2-amino benzamide with dimethyl sulfoxide (DMSO) as a carbon source and H2O2 as an effective oxidant. Mechanistically, the reaction proceeds through the radical approach with DMSO as one carbon source. To further substantiate the synthetic claim, the synthetic protocol has been extended to the synthesis of the anti-endotoxic active compound 3-(2-carboxyphenyl)-4-(3H)-quinazolinone.

Recent Advances in the Green Synthesis of Active N-Heterocycles and Their Biological Activities

N-heterocyclic scaffolds represent a privileged architecture in the process of drug design and development. It has widespread occurrence in synthetic and natural products, either those that are established or progressing as potent drug candidates. Additionally, numerous novel N-heterocyclic analogues with remarkable physiological significance and extended pharmaceutical applications are escalating progressively. Hence, the classical synthetic protocols need to be improvised according to modern requirements for efficient and eco-friendly approaches. Numerous methodologies and technologies emerged to address the green and sustainable production of various pharmaceutically and medicinally important N-heterocyclic compounds in last few years. In this context, the current review unveils greener alternatives for direct access to categorically differentiated N-heterocyclic derivatives and its application in the establishment of biologically active potent molecules for drug design. The green and sustainable methods accentuated in this review includes microwave-assisted reactions, solvent-free approaches, heterogeneous catalysis, ultrasound reactions, and biocatalysis.

One-Pot Synthesis of Isoxazole-Fused Tricyclic Quinazoline Alkaloid Derivatives via Intramolecular Cycloaddition of Propargyl-Substituted Methyl Azaarenes under Metal-Free Conditions

A practical method was developed for the convenient synthesis of isoxazole-fused tricyclic quinazoline alkaloids. This procedure accesses diverse isoxazole-fused tricyclic quinazoline alkaloids and their derivatives via intramolecular cycloaddition of methyl azaarenes with tert-butyl nitrite (TBN). In this method, TBN acts as the radical initiator and the source of N-O. Moreover, this protocol forms new C-N, C-C, and C-O bonds via sequence nitration and annulation in a one-pot process with broad substrate scope and functionalization of natural products.

Designing a new method for growing metal-organic framework (MOF) on MOF: synthesis, characterization and catalytic applications

Metal-organic frameworks as a unique class of high-surface-area materials have gained considerable attention due to their characteristic properties. In this perspective, herein, we report an eco-friendly and inexpensive route for the synthesis of 4(3H)-quinazolinones using magnetically separable core-shell-like bimetallic Fe₃O₄-MAA@Co-MOF@Cu-MOF NPs as environmentally-friendly heterogeneous catalysts. To the best of our knowledge, this is the first example of the integration of two different types of MOFs, which contain two different metal ions (Co²⁺ in the core and Cu²⁺ in the shell) using an external ligand. Our study not only introduces a novel nanostructured catalyst for the organic reaction but also presents a new strategy for the combination of two MOFs in one particle at the nanometer level. To survey the structural and compositional features of the synthesized nanocatalyst, a variety of spectroscopic and microscopic techniques including FT-IR, XRD, BET, TEM, HR-TEM, FE-SEM, EDX, EDX-mapping, TGA, VSM, and ICP-OES were employed. The combination of magnetic Co-MOF with Cu-MOF leads to achieving unique structural and compositional properties for Fe₃O₄-MAA@Co-MOF@Cu-MOF NPs with a particle size of 20-70 nm, mesostructure, and relatively large specific surface area (236.16 m² g^-1). The as-prepared nanostructured catalyst can be an excellent environment catalyst for the synthesis of a wide library of 4(3H)-quinazolinones derivatives, including electron-donating and electron-withdrawing aromatic, heteroaromatic, and aliphatic compounds under solvent-free conditions much better than the parent precursors. Moreover, by investigating the longevity of the nanocatalyst, the conclusion could be derived that the aforesaid nanocatalyst is stable under reaction conditions and could be recycled for at least seven recycle runs without a discernible decrease in its catalytic activity.

Synthesis of Quinazolinone-Fused Tetrahydroisoquinolines and Related Polycyclic Scaffolds by Iodine-Mediated sp3 C-H Amination

An iodine-mediated intramolecular sp³ C-H amination reaction producing quinazolinone-fused polycyclic skeletons from 2-aminobenzamide precursors is reported. This reaction does not use transition metals, has a broad substrate scope, and can be used on a gram scale. Under the optimal reaction conditions, a variety of quinazolinone-fused tetrahydroisoquinolines and derivatives of Rutaecarpine were synthesized from readily accessible compounds. The reaction proceeds well with crude 2-aminobenzamide derivatives, allowing for the synthesis of the products from simple 2-aminobenzoic acids and tetrahydroisoquinolines without purification of the 2-aminobenzamide intermediates. Preliminary biological experiments have identified Cereblon (CRBN) inhibitory activity and relevant anti-myeloma medicinal properties in some of these polycyclic products.

Tandem C-C/C-N Bond Formation via Rh(III)-Catalyzed α-Fluoroalkenylation and Sequential Annulation of 2-Arylquinazolinones and gem-Difluorostyrenes

An efficient method of Rh(III)-catalyzed coupling reaction between 2-arylquinazolinones and gem-difluorostyrenes has been developed. In this work, two diverse structures of monofluoroalkenes and isoindolo[1,2-b]quinazolin-10(12H)-one derivatives were respectively synthesized by controlling the amount of additives (Ca(OH)₂ and AgNTf₂) to achieve controlled stepwise breaking of the C-F bonds of gem-difluorostyrenes. This reaction has the characteristics of a wide range of substrates and good functional group tolerance. Meanwhile, several control experiments were conducted and a plausible mechanism was proposed.

Advances in anticancer alkaloid-derived metallo-chemotherapeutic agents in the last decade: Mechanism of action and future prospects

Metal-based complexes have occupied a pioneering niche in the treatment of many chronic diseases, including various types of cancers. Despite the phenomenal success of cisplatin for the treatment of many solid malignancies, a limited number of metallo-drugs are in clinical use against cancer chemotherapy till date. While many other prominent platinum and non‑platinum- based metallo-drugs (e.g. NAMI-A, KP1019, carboplatin, oxaliplatin, titanocene dichloride, casiopeinas® etc) have entered clinical trials, many have failed at later stages of R&D due to deleterious toxic effects, intrinsic resistance and poor pharmacokinetic response and low therapeutic efficacy. Nonetheless, research in the area of medicinal inorganic chemistry has been increasing exponentially over the years, employing novel target based drug design strategies aimed at improving pharmacological outcomes and at the same time mitigating the side-effects of these drug entities. Over the last few decades, natural products became one of the key structural motifs in the anticancer drug development. Many eminent researchers in the area of medicinal chemistry are devoted to develop new 3d-transition metal-based anticancer drugs/repurpose the existing bioactive compounds derived from myriad pharmacophores such as coumarins, flavonoids, chromones, alkaloids etc. Metal complexes of natural alkaloids and their analogs such as luotonin A, jatrorrhizine, berberine, oxoaporphine, 8-oxychinoline etc. have gained prominence in the anticancer drug development process as the naturally occurring alkaloids can be anti-proliferative, induce apoptosis and exhibit inhibition of angiogenesis with better healing effect. While some of them are inhibitors of ERK signal-regulated kinases, others show activity based on cyclooxygenases-2 (COX-2) and telomerase inhibition. However, the targets of these alkaloid complexes are still unclear, though it is well-established that they demonstrate anticancer potency by interfering with multiple pathways of tumorigenesis and tumor progression both in vitro and in vivo. Over the last decade, many significant advances have been made towards the development of natural alkaloid-based metallo-drug therapeutics for intervention in cancer chemotherapy that have been summarized below and reviewed in this article.

Divergent Approach for Regioselective Synthesis of Linearly and Angularly Fused Benzoimidazoquinazolinones from Isatoic Anhydrides

Ph₃P-I₂-mediated condensation reactions of isatoic anhydrides and o-phenylenediamines have been developed for the regioselective syntheses of a wide range of linearly and angularly fused benzoimidazoquinazolinones. The selectivity of the products relies on the generation of either highly electrophilic oxyphosphonium or less reactive imidate intermediates. A direct amine attack at the C-2 position of the oxyphosphonium intermediate presumably drives the reaction toward the linearly fused products, whereas an attack of the diamine at the C-4 position of the in situ generated cyclic imidate leads to the angularly fused derivatives. This strategy serves as a practical handle for the efficient synthesis of other related heterocycles.

A Computational QSAR, Molecular Docking and In Vitro Cytotoxicity Study of Novel Thiouracil-Based Drugs with Anticancer Activity against Human-DNA Topoisomerase II

Computational chemistry, molecular docking, and drug design approaches, combined with the biochemical evaluation of the antitumor activity of selected derivatives of the thiouracil-based dihydroindeno pyrido pyrimidines against topoisomerase I and II. The IC50 of other cell lines including the normal human lung cell line W138, lung cancer cell line, A549, breast cancer cell line, MCF-7, cervical cancer, HeLa, and liver cancer cell line HepG2 was evaluated using biochemical methods. The global reactivity descriptors and physicochemical parameters were computed, showing good agreement with the Lipinski and Veber's rules of the drug criteria. The molecular docking study of the ligands with the topoisomerase protein provides the binding sites, binding energies, and deactivation constant for the inhibition pocket. Various biochemical methods were used to evaluate the IC50 of the cell lines. The QSAR model was developed for colorectal cell line HCT as a case study. Four QSAR statistical models were predicted between the IC50 of the colorectal cell line HCT to correlate the anticancer activity and the computed physicochemical and quantum chemical global reactivity descriptors. The predictive power of the models indicates a good correlation between the observed and the predicted activity.

Facile One-Pot Synthesis of Functionalized Quinoline-Fused Fluorescent Dihydro/Spiro-quinazolinone Derivatives

A facile and efficient method has been developed for the synthesis of quinoline-fused fluorescent dihydro/spiro-quinazolinones. A plausible mechanism involving an acid-mediated enaminone intermediate is provided. The reaction proceeded using p-toluene sulfonic acid as a green promoter. The methodology was successful in synthesizing various quinoline-appended spiro-quinazolinones 4a-o. The synthetic utility of compounds 4a-o was demonstrated by synthesizing compounds 6a-d via Suzuki coupling as a key reaction. Significantly, the π-π* electronic transition of compounds 4c and 4k showed a blue shift. The molar extinction coefficient (ε), Stoke's shift (Δu̅), and quantum yield (Φ^f)_c were calculated for these derivatives (4c and 4k).

The design and discovery of topoisomerase I inhibitors as anticancer therapies

INTRODUCTION

Cancer has been identified as one of the leading causes of death worldwide. The biological target of some anticancer agents is topoisomerase I, an enzyme involved in the relaxation of supercoiled DNA. The synthesis of new compounds with antiproliferative effect and behaving as topoisomerase I inhibitors has become an active field of research. Depending on their mechanism of inhibition, they can be classified as catalytic inhibitors or poisons.

AREAS COVERED

This review article summarizes the state of the art for the development of selective topoisomerase I inhibitors. Collected compounds showed inhibition of the enzyme, highlighting those approved for clinical use, the combination therapies developed, as well as related drawbacks and future focus.

EXPERT OPINION

Research related to topoisomerase I inhibitors in cancer therapy started with camptothecin (CPT). This compound was first selected as a good anticancer agent and then topoisomerase I was identified as its therapeutic target. Derivatives of CPT irinotecan, topotecan, and belotecan are the only clinically approved inhibitors. Currently, their limitations are being addressed by different stretegies. Future studies should focus not only on developing other active molecules but also on improving the bioavailability and pharmacokinetics of potent synthetic derivatives.

Biology of quinoline and quinazoline alkaloids

Quinoline and quinazoline alkaloids, two important classes of N-based heterocyclic compounds, have attracted scientific and popular interest worldwide since the 19th century. More than 600 compounds have been isolated from nature to date. To build on our two prior reviews, we reexamined the promising molecules described in previous reports and provided updated literature on novel quinoline and quinazoline alkaloids isolated over the past 5 years. This chapter reviews and discusses 205 molecules with a broad range of bioactivities, including antiparasitic and insecticidal, antibacterial and antifungal, cardioprotective, antiviral, anti-inflammatory, and other effects. This survey should provide new clues or possibilities for the discovery of new and better drugs from the original naturally occurring quinoline and quinazoline alkaloids.

Rapid Synthesis of Luotonin A Derivatives via Synergistic Visible-Light Photoredox and Acid Catalysis

The merging of visible-light photoredox and acid catalysis allowed for an intramolecular Povarov cycloaddition reaction using eosin Y as the photocatalyst and TsOH·H₂O as the co-catalyst. A visible-light-promoted dehydrogenative cyclization protocol enabled the construction of Luotonin A derivatives with up to 97% yield.

Synthesis of N-Fused Triazole-Piperazine-Quinazolinones via One-Pot Tandem Click Reaction and Cross-Dehydrogenative Coupling

Herein, a one-pot protocol to synthesize tetracyclic triazole-piperazine-quinazolinone-fused N-heterocyclic scaffolds is reported. In this strategy, a tandem approach of two highly efficient synthetic reactions, click and cross-dehydrogentive coupling reactions, with high atom economy were employed to obtain the target N-fused scaffolds. Being highly functional group tolerable, this method has broad substrate scope. Interestingly, some of these derivatives showed strong white solid-state fluorescence.

Iodine-mediated electrochemical C(sp3)-H cyclization: the synthesis of quinazolinone-fused N-heterocycles

An efficient iodine-mediated electrochemical C(sp³)-H cyclization was developed under mild conditions. A variety of functionalized quinazolinone-fused N-heterocycles can be obtained with good to excellent yields by virtue of this method. The reaction features a broad substrate scope and scalability, and is metal-free and chemical oxidant-free.

Design, Synthesis, and Antifungal Evaluation of Luotonin A Derivatives against Phytopathogenic Fungi

Crop diseases caused by fungi threaten food security and exacerbate the food crisis. Inspired by the application of fungicide candidates from natural products in agrochemical discovery, a series of luotonin A derivatives were designed, synthesized, and evaluated for their antifungal activities against five plant fungi. Most of these compounds exhibited significant fungicidal activity against Botrytis cinerea in vitro with EC₅₀ values less than 1 μg/mL. Among them, compounds w7, w8, w12, and w15 showed superior antifungal activity against B. cinerea with EC₅₀ values of 0.036, 0.050, 0.042, and 0.048 μg/mL, respectively, which were more potent than boscalid (EC₅₀ = 1.790 μg/mL). Preliminary mechanism studies revealed that compound w7 might pursue its antifungal activity by disrupting the fungal cell membrane and cell wall. Moreover, in vivo bioassay also indicated that compound w7 could be effective for the control of B. cinerea. The above results evidenced the potential of luotonin A derivatives as novel and promising candidate fungicides.

Advances in Green Catalysis for the Synthesis of Medicinally Relevant N-Heterocycles

N-heterocycles, both saturated and unsaturated, are ubiquitous biologically active molecules that are extremely appealing scaffolds in drug discovery programs. Although classical synthetic methods have been developed to access many relevant N-heterocyclic scaffolds, representing well-established and reliable routes, some do not meet the needs of sustainability. In this context, several advances have been made towards the sustainable synthesis of N-heterocycles. This review focuses on the most recent examples from the last five years of catalytic synthesis of several heterocyclic compounds of medicinal relevance. Thus, the synthesis of isoindoloquinazolines, quinazolines and azaindoles, among others, are covered. The synthetic methods selected include the use of homogeneous and heterogeneous catalysts and the use of alternative and sustainable methods such as, for example, metal-catalyzed acceptorless coupling and one-pot reactions. The green aspects of the individual synthetic approaches are highlighted, and the scope of each methodology is described.

Design and synthesis of C-aryl angular luotonins via a one-pot aza-Nazarov-Friedlander sequence and their Topo-I inhibition studies along with C-aryl vasicinones and luotonins

A facile one-pot synthesis of C-ring substituted angular luotonins has been realized via a methanesulfonic acid mediated aza-Nazarov-Friedlander condensation sequence on quinazolinonyl enones. Topoisomerase I (topo-I) inhibition studies revealed that the angular luotonin library (7a-7l) and their regioisomeric analogs (linear luotonins, 8a-8l) are weak negative modulators, compared to camptothecin. These results would fare well for the design of topo-I-inert luotonins for non-oncological applications such as anti-fungal and insecticide lead developments. Surprisingly, the tricyclic vasicinones (9h, 9i, and 9j) showed better topo-I inhibition compared to pentacyclic C-aryl luotonins providing a novel pharmacophore for further explorations.

Electrochemical synthesis of quinazolinone via I2-catalyzed tandem oxidation in aqueous solution

The development of protocols for synthesizing quinazolinones using biocompatible catalysts in aqueous medium will help to resolve the difficulties of using green and sustainable chemistry for their synthesis. Herein, using I₂ in coordination with electrochemical synthesis induced a C-H oxidation reaction which is reported when using water as the environmentally friendly solvent to access a broad range of quinazolinones at room temperature. The reaction mechanism strongly showed that I₂ cooperates electrochemically promoted the oxidation of alcohols, then effectively cyclizing amides to various quinazolinones.

A patent review of topoisomerase I inhibitors (2016-present)

INTRODUCTION

Topoisomerases are important targets for therapeutic improvement in the treatment of some diseases, including cancer. Inhibitors and poisons of topoisomerase I can limit the activity of this enzyme in its enzymatic cycle. This fact implies an anticancer effect of these drugs, since most cancer cells are characterized by both a higher activity of topoisomerase I and a higher replication rate compared to non-cancerous cells. Clinically approved inhibitors include camptothecin (CPT) and its derivatives. However, their limitations have encouraged different research groups to prepare new compounds, proof of which are the numerous research works and patents, some of them in the last five years.

AREAS COVERED

This review covers patent literature on topoisomerase I inhibitors and their application published between 2016-present.

EXPERT OPINION

The highest contribution toward patent development has been obtained from academics or small biotechnology companies. The most important fields of innovation include the preparation of prodrugs or inhibitors combined with other agents, as biocompatible polymers or antibodies. A promising development of topoisomerase I inhibitors is expected in the next years, directed to the treatment of diverse diseases, specifically toward different types of cancer and infectious diseases, among others.

Electrochemically induced synthesis of quinazolinones via cathode hydration of o-aminobenzonitriles in aqueous solutions

An efficient and practical electrochemically catalyzed transition metal-free process for the synthesis of substituted quinazolinones from simple and readily available o-aminobenzonitriles and aldehydes in water has been accomplished. I₂/base and water play an unprecedented and vital role in the reaction. By electrochemically catalysed hydrolysis of o-aminobenzonitriles, the synthesis of quinazolinones with benzaldehyde was first proposed. The synthetic utility of this method was demonstrated by gram-scale operation, as well as the preparation of bioactive N-(2,5-dichlorophenyl)-6-(2,2,2-trifluoroethoxy) pteridin-4-amine, which enables straightforward, practical and environmentally benign quinazolinone formation.

Aerobic primary and secondary amine oxidation cascade by a copper amine oxidase inspired catalyst

A CAO inspired catalyst catalyzed the cascade aerobic oxidation of primary and secondary amines for the synthesis of quinazolin-4(3H)-one core in high yields. Like the natural CAOs, a copper ion improves the o-quinone cofactor's catalytic activity.

Organocatalyzed Synthesis of Highly Functionalized Phthalimides via Diels-Alder Reaction Employing Two Dienophiles

An efficient and facile protocol for the synthesis of biologically and pharmaceutically important phthalimides is developed by l-proline-catalyzed reaction between two dienophiles of α,β-unsaturated aldehydes and maleimides. The reaction involves an efficient benzannulation that proceeds via a formal [4 + 2] cycloaddition of azadiene intermediates generated in situ from enals and N-substituted maleimides. This protocol provides a variety of functionalized phthalimide derivatives, including a potent COX-2 enzyme inhibitor.

Luotonin A and Its Derivatives as Novel Antiviral and Antiphytopathogenic Fungus Agents

Plant diseases caused by viruses and fungi have posed a serious threat to global agricultural production. The discovery of new leads based on natural products is an important way to innovate pesticides. In this work, natural product luotonin A was found to have good antiviral activity against tobacco mosaic virus (TMV) for the first time. A series of luotonin A derivatives were designed, synthesized, and evaluated for their antiviral activities and fungicidal activities systematically. Most compounds displayed better antiviral activities against TMV than commercial ribavirin. Compounds 9k, 12b, and 12d displayed about similar inhibitory effects as ningnanmycin (inhibitory rates of 55, 57, and 59% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively), the best antiviral agent at present, and emerged as novel antiviral leads for further research. We selected 9k for further antiviral mechanism research via transmission electron microscopy and molecular docking, which revealed that compound 9k can interact with TMV coat protein through the hydrogen bond, leading to its polymerization, thus preventing virus assembly. Further fungicidal activity tests showed that these compounds also showed broad-spectrum fungicidal activities against 14 kinds of phytopathogenic fungi. Especially, compound 14 with a 100% antifungal effect against Botrytis cinereal emerged as a lead for further research. This work provides a reference for the development of agricultural active ingredients based on Chinese medicine plants.