Synthesis and biological evaluation of 3-alkoxy analogues of flavone-8-acetic acid

Photoredox-Catalyzed Tandem Cyclization of Enaminones with N-Sulfonylaminopyridinium Salts toward the Synthesis of 3-Sulfonaminated Chromones

A photoredox-catalyzed intermolecular tandem sulfonamination/cyclization of enaminones was realized by using N-aminopyridinium salts as the sulfonaminated reagents without transition-metal catalysts or bases. The reaction exhibits a broad scope and good functional group tolerance, good yields, and regioselectivity. Preliminary mechanistic studies support the radical property of the reaction and the involvement of N-centered radical intermediates.

Selectfluor-mediated tandem cyclization of enaminones with diselenides toward the synthesis of 3-selenylated chromones

A practical and metal-free approach for the regioselective selenation of chromones employing Selectfluor reagent under mild conditions is described. The developed method is suitable for a wide substrate scope and affords 3-selenylated chromones in good to excellent yield with high selectivity. An ionic mechanism is proposed for this transformation. Furthermore, the application of potassium thiocyanate with enaminones for the synthesis of thiocyano chromones in this transformation is also successful.

Natural-like Chalcones with Antitumor Activity on Human MG63 Osteosarcoma Cells

Osteosarcoma (OS) is a malignant disease characterized by poor prognosis due to a high incidence of metastasis and chemoresistance. Recently, Licochalcone A (Lic-A) has been reported as a promising agent against OS. Starting from chalcones selected from a wide in-house library, a new series was designed and synthetized. The antitumor activity of the compounds was tested on the MG63 OS cell line through the innovative Quantitative Phase Imaging technique and MTT assay. To further investigate the biological profile of active derivatives, cell cycle progression and apoptosis induction were evaluated. An earlier and more consistent arrest in the G2-M phase with respect to Lic-A was observed. Moreover, apoptosis was assessed by Annexin V staining as well as by the detection of typical morphological features of apoptotic cells. Among the selected compounds, 1e, 1q, and 1r proved to be the most promising antitumor molecules. This study pointed out that an integrated methodological approach may constitute a valuable platform for the rapid screening of large series of compounds.

Destruction of tumor vasculature by vascular disrupting agents in overcoming the limitation of EPR effect

Nanomedicine greatly improves the efficiency in the delivery of antitumor drugs into the tumor, but insufficient tumoral penetration impairs the therapeutic efficacy of most nanomedicines. Vascular disrupting agent (VDA) nanomedicines are distributed around the tumor vessels due to the low tissue penetration in solid tumors, and the released drugs can selectively destroy immature tumor vessels and block the supply of oxygen and nutrients, leading to the internal necrosis of the tumors. VDAs can also improve the vascular permeability of the tumor, further increasing the extravasation of VDA nanomedicines in the tumor site, markedly reducing the dependence of nanomedicines on the enhanced permeability and retention effect (EPR effect). This review highlights the progress of VDA nanomedicines in recent years and their application in cancer therapy. First, the mechanisms of different VDAs are introduced. Subsequently, different strategies of delivering VDAs are described. Finally, multiple combination strategies with VDA nanomedicines in cancer therapy are described in detail.

Flavonoid-Inspired Vascular Disrupting Agents: Exploring Flavone-8-Acetic Acid and Derivatives in the New Century

Naturally occurring flavonoids are found as secondary metabolites in a wide number of plants exploited for both medicine and food and have long been known to be endowed with multiple biological activities, making them useful tools for the treatment of different pathologies. Due to the versatility of the scaffolds and the vast possibilities of appropriate decoration, they have also been regarded as fruitful sources of lead compounds and excellent chemical platforms for the development of bioactive synthetic compounds. Flavone-8-acetic acid (FAA) and 5,6-dimethylxanthone acetic acid (DMXAA) emerged for their antitumour potential due to the induction of cytokines and consequent rapid haemorrhagic necrosis of murine tumour vasculature, and different series of derivatives have been designed thereafter. Although the promising DMXAA failed in phase III clinical trials because of strict species-specificity, a boost in research came from the recent identification of the stimulator of interferon genes (STING), responsible for supporting tumoural innate immune responses, as a possible biological target. Consequently, in the last decade a renewal of interest for these flavonoid-based structures was noticed, and novel derivatives have been synthesised and evaluated for a deeper understanding of the molecular features needed for affecting human cells. Undoubtedly, these natural-derived molecules deserve further investigation and still appear attractive in an anticancer perspective.

A novel one-pot synthesis of flavones

In this paper, a one-pot facile route for the BiCl₃/RuCl₃-mediated synthesis of functionalized flavones is described, including: (i) intermolecular ortho-acylation of substituted phenols with cinnamoyl chlorides, and (ii) intramolecular cyclodehydrogenation of the resulting o-hydroxychalcones. The reaction conditions are discussed herein.

A one-pot facile route for the BiCl₃/RuCl₃-mediated synthesis of functionalized flavones is described, including: (i) ortho-acylation of phenols with cinnamoyl chlorides, and (ii) cyclodehydrogenation of the resulting o-hydroxychalcones.

Synthesis and crystal structure of methyl 2-(2-((tert-butoxycarbonyl)amino)phenyl)-2-(4-oxo-4H-chromen-3-yl)acetate, C23H23NO6

C23H23NO6, monoclinic, P21/n (no. 14), a = 7.5845(4) Å, b = 14.7024(5) Å, c = 18.1433(6) Å, β = 98.753(4)°, V = 1999.62(14) Å3, Z = 4, R gt(F) = 0.0389, wR ref(F 2) = 0.0965, T = 293 K.

Straightforward Synthesis of 3-Selenocyanato-Substituted Chromones through Electrophilic Selenocyanation of Enaminones under Grinding Conditions

A metal- and oxidant-free method for preparing 3-selenocyanato-substituted chromones from 2-hydroxyphenyl enaminones by using a newly developed electrophilic selenocyanating reagent is reported­. A series of 3-selenocyanato- or 3-thiocyanato-substituted chromones, as well as 3-selenocyanato- or 3-thiocyanato-substituted quinolinones was obtained in good to excellent yields under grinding reaction conditions. The generality and utility of this approach were demonstrated by a scale-up reaction and transformations of one of the products.

Design and synthesis of novel Flavone-based histone deacetylase inhibitors antagonizing activation of STAT3 in breast cancer

Histone deacetylases (HDACs) inhibitors have demonstrated a great clinical achievement in hematological malignancies. However, the efficacy of HDACs inhibitors in treating solid tumors remains limited due to the complicated tumor microenvironment. In this study, we designed and synthesized a class of novel HDACs inhibitors based on the structure of flavones and isoflavones, followed by biological evaluation. To be specific, a lead compound 15a was discovered with strong anti-proliferative effects on a variety of solid tumor cells, especially for breast cancer cells with resistance to SAHA. Studies demonstrated that 15a could significantly inhibit the activity of HDAC 1, 2, 3 (class I) and 6 (class IIB), leading to a dose-dependent accumulation of acetylated histones and α-Tubulin, cell cycle arrest (G1/S phase) and apoptosis in breast cancer cells. Furthermore, the lead compound 15a could also antagonize the activation of STAT3 induced by HDACs inhibition in some breast cancer cells, which further reduced the level of pro-survive proteins in tumor cells and enhanced anti-tumor activity regulated by STAT3 signaling in vivo. Overall, our findings demonstrated that the novel compound 15a might be a HDACs inhibitor candidate, which could be used as promising chemotherapeutic agent for breast cancer.

Metal-free Brønsted acid mediated synthesis of fully substituted thiophenes via chemo- and regioselective intramolecular cyclization of α,α′-bis(β-oxodithioesters) at room temperature

Metal-free Brønsted acid mediated synthesis of tetrasubstituted thiophenes via intramolecular cyclization of α,α′-bis(β-oxodithioesters) is devised at room temperature.

Recent advances in vascular disrupting agents in cancer therapy

Vascular disrupting agents (VDAs) are an important class of compounds that exhibit selective activity against pre-existing tumor vasculature, causing rapid shutdown of the tumor blood flow and consequent necrosis of the tumor mass. The VDAs can be divided into flavonoid compounds, which are related to flavone acetic acid, and tubulin-binding agents. Tubulin-binding agents represent the largest group of VDAs and are characterized by different chemical structures, although most of them are derivatives of the lead compound combretastatin (CA-4). They demonstrated clinical activity, although recent findings have established that they have insufficient activity as single agents. Several resistance mechanisms occur, such as the resistance of the tumor rim cells, while promising results have been described in combination with other chemotherapeutics.

Development of environmentally sensitive fluorescent and dual emissive deoxyuridine analogues

We designed and developed fluorescent deoxyuridine analogues with strong sensitivity to hydration for the major groove labelling of DNA.

Synthesis and anticancer activities of 3-arylflavone-8-acetic acid derivatives

This paper describes the synthesis and the antiproliferative activities of compounds 9a-r, 3-aryl analogs of flavone-8-acetic acid that bear diverse substituents on the benzene rings at the 2- and 3-positions of the flavone nucleus. Their direct and indirect cytotoxicities were evaluated against HT-29 human colon adenocarcinoma cell lines, A549 lung adenocarcinoma cell lines and Human Peripheral Blood Mononuclear Cells (HPBMCs). The results indicate that most of the compounds bearing electron-withdrawing substituents (9b-m) exhibited moderate direct cytotoxicities. And compounds 9e and 9i showed comparable indirect cytotoxicities with 5, 6-dimethylxanthenone-4-acetic acid (DMXAA), and low direct cytotoxicities toward HPBMCs. Interestingly, the compounds 9n-r bearing methoxy groups at the 2- or 3-position of the flavone nucleus exhibited higher indirect cytotoxicities against A549 cell lines than DMXAA, and lower cytotoxicities against HPBMCs. In addition, compounds 9p-r were found to be able to induce tumor necrosis factor α (TNF-α) production in HPBMCs.

Synthesis, selective cytotoxicities and probable mechanism of action of 7-methoxy-3-arylflavone-8-acetic acids

Thirteen new analogues of flavone-8-acetic acid, that is, compounds 10a-m bearing a methoxy group at the 7-position and diverse subsitiuents on the benzene ring at the 2- and 3-positions of flavone nucleus, were synthesized and evaluated for their direct antiproliferative effects on two human tumor cell lines and for their indirect antiproliferative activities in the transwell co-culture system. The results indicated that most of compounds 10a-m showed moderate direct cytotoxicities. Among them, compound 10i exhibited higher direct cytotoxicity and selectivity for both cell lines over BJ human foreskin fibroblast cells than 5,6-dimethylxanthenone-4-acetic acid (DMXAA). Interestingly, compared with DMXAA, compound 10e showed comparable indirect cytotoxicity and higher selectivity. In addition, compound 10e was found to be able to induce tumor necrosis factor α (TNF-α) production in human peripheral blood mononuclear cells.

Sodium Selenite-dimethylsulfoxide: A Highly Efficient Reagent for Dehydrogenation

Sodium selenite in dimethylsulfoxide is a highly efficient reagent for dehydrogenation reactions and can be used under both thermal as well as microwave irradiation conditions. Using this reagent benzoins have been dehydrogenated to benzils, flavanones to flavones and 2′-hydroxy chalcones have been converted into flavones by cyclodehydrogenation.

Synthesis of 2,3,6,8-tetrasubstituted chromone scaffolds

A useful and efficient synthetic strategy to 2,3,6,8-tetrasubstituted chromone derivatives has been developed. 2-Aryl/styryl-8-bromo-6-chloro-3-hydroxychromone derivatives were synthesized and used as scaffolds by introducing a variety of substituents in the 3-, 6-, and 8-positions using palladium-mediated reactions. Excellent regioselectivity in all positions could be obtained by performing reactions in the 8-position first, in which Stille, Heck, Suzuki, and Sonogashira reactions gave good to excellent yields of product (63-98%). Stille and Heck reactions in the 6-position also gave the desired products in good yields (64-86%). The hydroxy group in the 3-position was activated as a triflate and used in productive Stille reactions (63-94%). This hydroxyl group was also used in O-alkylation reactions with different functionalized alkyl bromides (57-88%). The flavonoids, which are based on the chromone structure, and other related ring systems, have several interesting biological activities. The chromones are also interesting structural scaffolds, and they have for example been designed to be used as mimetics of short peptides. The versatile applicability of chromone derivatives and especially their potential use in drug discovery implicates the importance of access to efficient synthetic routes to such compounds.

Vascular disrupting agents

A clear definition for vascular targeting agents (VTAs) and vascular disrupting agents (VDAs) has separated the two as distinct methods of cancer treatment. VDAs differ from VTAs (antiangiogenesis drugs) in their mechanism of action. VTAs attempt to keep new blood vessels from forming and do not act on blood vessels that already feed existing tumors. In contrast, VDAs cause the vascular structure inside a solid tumor to collapse, depriving the tumor of blood and oxygen it needs to survive. Therefore, VDAs are an attractive way to approach the cancer problem by combating developed tumors. The following review discusses six small molecule VDAs, namely DMXAA, ZD6126, TZT1027, CA4P, AVE8062, and Oxi4503, their synthesis, biological mechanism of action, and current clinical status.

New derivatives of xanthenone-4-acetic acid: synthesis, pharmacological profile and effect on TNF-alpha and NO production by human immune cells

New derivatives of xanthenone-4-acetic acid, bearing an alkoxy chain of variable length and a basic moiety, were synthesised in order to test the influence of this additional function on antitumour activity. The introduction of bulky substituents carrying a basic nitrogen seems to be somewhat tolerated, since for some of the compounds the enhancement of lytic potential of human monocytes was comparable to that of the reference molecule DMXAA. The induction of the release of TNF-alpha and nitric oxide by human monocytes, as well as the hypothesis of a potentiation of the activity of lipopolysaccharide in the induction of those cytotoxic factors, was also evaluated. In this respect, the most interesting compound (6a) exhibited the same spectrum of biological activity shown by DMXAA and seems therefore to be endowed with the same mechanism of action of the reference compound.

Synthesis and biological study of a flavone acetic acid analogue containing an azido reporting group designed as a multifunctional binding site probe

Flavone-8-acetic acid (FAA) is a potent immunomodulatory small molecule that is uniquely characterized as being active on mouse but not human cells. Although FAA is a potent inducer of murine cytokine, chemokine and interferon gene expression, its mode of action remains unknown. In this report, we describe the synthesis of a new flavone acetic acid (FAA) analogue, (2-[2-(4-azidophenyl)-4-oxochromen-8-yl-]acetic acid (compound 2). We demonstrate that compound 2 is equally active as the parent FAA in inducing chemokine gene expression and that the azide functional group is capable of reacting with a reporter molecule, such as the FLAG peptide-phosphine, under mild conditions. This reaction will be useful for detecting the drug-bound protein active complex utilizing an anti-FLAG antibody.