Furan Skeleton Research Articles

Synthesis and Biological Evaluation of Novel 2-Aroyl Benzofuran-Based Hydroxamic Acids as Antimicrotubule Agents.

Because of synergism between tubulin and HDAC inhibitors, we used the pharmacophore fusion strategy to generate potential tubulin-HDAC dual inhibitors. Drug design was based on the introduction of a N-hydroxyacrylamide or a N-hydroxypropiolamide at the 5-position of the 2-aroylbenzo[b]furan skeleton, to produce compounds 6a-i and 11a-h, respectively. Among the synthesized compounds, derivatives 6a, 6c, 6e, 6g, 11a, and 11c showed excellent antiproliferative activity, with IC50 values at single- or double-digit nanomolar levels, against the A549, HT-29, and MCF-7 cells resistant towards the control compound combretastatin A-4 (CA-4). Compounds 11a and 6g were also 10-fold more active than CA-4 against the Hela cell line. When comparing the inhibition of tubulin polymerization versus the HDAC6 inhibitory activity, we found that 6a-g, 6i, 11a, 11c, and 11e, although very potent as inhibitors of tubulin assembly, did not have significant inhibitory activity against HDAC6.

Talarodrides A–F, Nonadrides from the Antarctic Sponge-Derived Fungus Talaromyces sp. HDN1820200

Six new nonadride derivatives, named talarodrides A-F (1-6), were isolated from the Antarctic sponge-derived fungus Talaromyces sp. HDN1820200. All structures including the absolute configurations were deduced by extensive spectroscopic analysis and computational ECD calculations. Compounds 1-4 share a rare caged bicyclo[4.3.1]-deca-1,6-diene with a bridgehead olefin and maleic anhydride core skeleton, while compounds 5 and 6 possess the first case of a naturally occurring 5/7/6 methanocyclonona[c]furan skeleton. Talarodride A (1) and talarodride B (2) showed selective inhibitory effects against Proteus mirabilis and Vibrio parahemolyticus with MICs of 3.13-12.5 μM.

Highly Efficient Synthesis of 2-Substituted Benzo[b]furan Derivatives from the Cross-Coupling Reactions of 2-Halobenzo[b]furans with Organoalane Reagents

AbstractA highly efficient and simple route for the synthesis of 2-substituted benzo[b]furans has been developed by palladium-catalyzed cross-coupling reaction of 2-halobenzo[b]furans with aryl, alkynyl, and alkylaluminum reagents. Various 2-aryl-, 2-alkynyl-, and 2-alkyl-substituted benzo[b]furan derivatives can be obtained in 23–97% isolated yields using 2–3 mol% PdCl2/4–6 mol% XantPhos as the catalyst under mild reaction conditions. The aryls bearing electron-donating or electron-withdrawing groups in 2-halobenzo[b]furans gave products in 40–97% isolated yields. In addition, aluminum reagents containing thienyl, furanyl, trimethylsilanyl, and benzyl groups worked efficiently with 2-halobenzo[b]furans as well, and three bioactive molecules with 2-substituted benzo[b]furan skeleton were synthesized. Furthermore, the broad substrates scope and the typical maintenance of vigorous efficiency on gram scale make this protocol a potentially practical method to synthesize 2-substituted benzo[b]furan derivatives. On the basis of the experimental results, a possible catalytic cycle has been proposed.

Cu-Catalyzed Dehydrogenative C-O Cyclization for the Synthesis of Furan-Fused Thienoacenes.

The first Cu-catalyzed dehydrogenative C-O cyclization for the synthesis of furan-fused thienoacenes is described. A variety of heteroacenes including a thieno[3,2-b]furan or a thieno[2,3-b]furan skeleton were synthesized by intramolecular C-H/O-H coupling. The use of a mixed solvent of N-methyl-2-pyrrolidone, ethylene glycol monomethyl ether, and toluene was essential for suppressing side reactions and efficiently promoting the reaction. Double C-O cyclization was also conducted to afford highly π-expanded furan-fused thienoacenes.

Study on fragmentation patterns of coumarins in Notopterygium inchum with ultrahigh performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry

To demonstrate the fragmentation patterns of simple coumarins furanocourmarin(C_7-C_8), furanocourmarin(C_6-C_7) and dihydrofuran coumarin by mass spectrometry, with fraxin, scopoletin, isopsoralen, pimpinellin, isoimperatorin, notopterol and noda-kenin as study subjects, so as to provide a basis for rapid identification of compounds in different subtypes of coumarins. Ultrahigh performance liquid chromatography combined with quardrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS) was implemented in both positive and negative ion modes. Masslynx software was employed to provide the elemental constituents of each detected ion based on its accurate molecular weight. Chemdraw 2014 was used to cultivate mass number of each inferred structure. The fragment pattern of each compound was determined based on the structures inferred from all the relevant ions. And the patterns were drawn by Chemdraw 2014. The deviation between the calculated molecular weight of the inferred structure and the detected value of the ions was used to assess the correctness of the inferred structures in the fragmentation patterns. The results showed that with UPLC-Q-TOF, neutral loss of CO_2 and CO was reflected in lactone and furan skeletons from the courmarin structure. An even mass was attributed to the loss of an odd number of methyl radicals from compounds with a methoxy substituent. Furanocourmarin(C_7-C_8) produced a protonated molecular ion([M+H]~+), while the other courmarin subtypes produced either a sodium adduct of the molecular ion([M+Na]~+) or a sodium adduct of the molecular ion([M+Na]~+) with a protonated molecular ion([M+H]~+). The m/z 203.03 was a diagnostic ion for furanocourmarin(C_6-C_7), and the m/z 147.04 was supplementary evidence for furanocourmarin(C_6-C_7) identification. The characteristic ion of furanocourmarin(C_7-C_8) was m/z 131.05, while m/z 187.04 was the characteristic ion of dihydrofuran coumarin. The m/z 203.03 ion for furanocourmarin(C_7-C_8) was pretty weak. In negative ion mode, furanocourmarin(C_7-C_8) did not have any signals that were different from the other subtypes of courmarins. The fragmentation patterns in negative ion mode for the other subtypes of courmarins were similar to those in positive ion mode. Four types of fragmentation patterns were identified as forcourmarins from Notopterygium inchum. This study provides the basis for the rapid identification of courmarin subtypes by mass spectrometry.

Nickel‐Catalyzed Acyl Group Transfer of o‐Alkynylphenol Esters Accompanied by C−O Bond Fission for Synthesis of Benzo[b]furan

AbstractHerein, we report the nickel‐catalyzed cascade C−O bond cleavage/cyclization of ortho‐alkynylphenyl ester to construct a 3‐acylbenzo[b]furan skeleton. As a result of reaction condition screening, the Ni(0)/IAd (1,3‐Di(1‐adamantyl)imidazole‐2‐ylidene) system was found to be optimal for catalytic conversion. Interestingly, the reaction exclusively gives 3‐acylbenzo[b]furan instead of a decarbonylated product frequently observed in reactions mediated by acyl‐nickel species. The catalyst loadings could be reduced to 5–10 mol %. We demonstrated the synthesis of a variety of functionalized 3‐acylbenzofuran derivatives. We conducted stoichiometric study of nickel complexes as well as density functional theory (DFT) calculations to support a possible reaction mechanism.

Recent Achievement in the Synthesis of Benzo[b]furans.

Benzo[b]furan derivatives are oxygen-containing heterocyclic compounds consisting of fused benzene and furan rings and are present in a large number of natural and non-natural compounds. This class of compounds has a wide spectrum of biological activities, such as antiarrhythmic, anticancer, inflammatory, antioxidant, antimicrobial, and antiviral. Furthermore, benzo[b]furan derivatives have also been applied in various areas, such as organic electroluminescence device materials and organic dyes, photosensitizing material, organic synthesis as building blocks or intermediates. Because of a broad range of applicability, the synthesis of benzo[b]furan derivative has drawn great attention of chemists and many studies on the synthesis of this class of compounds have been reported recently. This review will give an overview of benzo[b]furan preparation based on studies dating back to the year 2012. In this review, recent development in the synthesis of benzo[b]furans are discussed. There has been increasingly new methodologies for the construction of benzo[b]furans skeleton to improve efficiency or develop environmentally friendly procedures. In some studies, reaction mechanisms were also outlined. Many methods for the synthesis of benzo[b]furans have been reported recently. Most of them involve cyclization or cycloisomerization processes. Unquestionably, more imaginative strategies for the construction of benzo[b]furan skeleton will be established in the near future. Application of known methods to natural products or drug synthesis, on industrial scale for the synthesis of economically or medicinally important benzo[ b]furans will probably be paid attention to.

Design, synthesis, in vitro and in vivo biological evaluation of 2-amino-3-aroylbenzo[b]furan derivatives as highly potent tubulin polymerization inhibitors

A new class of inhibitors of tubulin polymerization based on the 2-amino-3-(3′,4′,5′-trimethoxybenzoyl)benzo[b]furan molecular scaffold was synthesized and evaluated for in vivo and in vitro biological activity. These derivatives were synthesized with different electron-releasing or electron-withdrawing substituents at one of the C-4 through C-7 positions. Methoxy substitution and location on the benzene part of the benzo[b]furan ring played an important role in affecting antiproliferative activity, with the greatest activity occurring with the methoxy group at the C-6 position, the least with the substituent at C-4. The same effect was also observed with ethoxy, methyl or bromine at the C-6 position of the benzo[b]furan skeleton, with the 6-ethoxy-2-amino-3-(3′,4′,5′-trimethoxybenzoyl)benzo[b]furan derivative 4f as the most promising compound of the series. This compound showed remarkable antiproliferative activity (IC50: 5 pM) against the Daoy medulloblastoma cell line, and 4f was nearly devoid of toxicity on healthy human lymphocytes and astrocytes. The potent antiproliferative activity of 4f was derived from its inhibition of tubulin polymerization by binding to the colchicine site. The compound was also examined for in vivo activity, showing higher potency at 15 mg/kg compared with the reference compound combretastatin A-4 phosphate at 30 mg/kg against a syngeneic murine mammary tumor.

Antiproliferative activity of naphthoquinones and indane carboxylic acids from lapachol against a panel of human cancer cell lines

Lapachol (1) is a well-studied natural product isolated from plants of the Bignoniaceae family and demonstrates diverse biological effects. Historically, chemical transformation of the lapachol scaffold has yielded new derivatives with impressive biological activity and rich chemical diversity. β-lapachone (2), α-lapachone (3), and 2-acetylfuronaphthoquinone (4) are examples of analogs derived from lapachol that show superior antitumor activity compared with the natural product. In the present study, novel indane carboxylic acid: 2,2-dimethyl-2,3-dihydroindeno[1,2-b]pyran-4,5-dione (9) and methyl 5-hydroxy-2,2-dimethyl-2,3,4,5-tetrahydroindeno[1,2-b]pyran-5-carboxylate (10) and naphthoquinone derivatives were synthesized from lapachol with structural similarities to the antitumor lapachol derivatives. The synthesized compounds were evaluated for antiproliferative activities against a panel of human cancer cell lines including in vitro models for neuroblastoma, melanoma, glioblastoma, and non-small cell lung cancer. As expected, the most potent derivatives were those incorporating β-naphthoquinone and α-naphthoquinono[2,3-b]furan skeletons. Many of these compounds possessed nanomolar to single digit micromolar antiproliferative potency. However, the most interesting analog evaluated was the dione 9 with an indeno[1,2-b]pyran skeleton, which demonstrated potent cytotoxic activity. The current investigation identified several new lead compounds that could be used as starting points for anticancer drug discovery.

Synthesis and biological evaluation of 3-functionalized 2-phenyl- and 2-alkylbenzo[b]furans as antiproliferative agents against human melanoma cell line

The key function of microtubules and mitotic spindle in cell division make them attractive targets in anticancer therapy. In the present study, functionalized in 3 position 2-phenyl- and 2-alkylbenzo[b]furans were synthesized and evaluated as antitumor agents. Among the synthesized derivatives 13a, 13b and 14 exhibited the most potent antiproliferative activity against human melanoma A375 cell line with IC50 values of 2.85 µM, 0.86 µM, 0.09 µM, respectively. The most promising compound defined was 14 with three methoxy groups in the 3-aroyl substituent and 7-methoxy group in 2-phenylbenzo[b]furan skeleton. Tubulin polymerization assay, confocal microscopy imaging and flow cytometry analysis revealed that 2-phenyl-3-aroylbenzo[b]furans (13a, 13b and 14) inhibited tubulin polymerization leading to disruption of mitotic spindle formation, cell cycle arrest in G2/M phase and apoptosis.

Formal [4 + 1] cycloaddition strategy for the synthesis of dihydrobenzofurans via Michael addition of 2-(2-nitrovinyl)-phenols and malonate esters (C1 synthon) and subsequent iodine-catalyzed oxidative annulation

A novel [4 + 1] cycloaddition protocol for the synthesis of dihydrobenzo(naphtho)furan skeletons from readily available 2-(2-nitrovinyl)-phen(naphth)ols and malonate esters via a tandem Michael addition/iodine-catalyzed oxidative annulation has been developed. This method provides a new and facile application of malonate esters as 1,1-nucleophilic/electrophilic type C1 synthons without a pre-functionalization step and the plausible reaction mechanism is proposed.

Progress in Total Syntheses of Anti‐malignant Pleural Mesothelioma Compounds

Malignant pleural mesothelioma (MPM) is a fatal tumor, which spreads aggressively and highly resists conventional chemotherapeutic agents. It continues to be a difficult clinical problem, and efficient treatment is still an enormous challenge. Alimta is used currently as an anti‐MPM medicine, obtained mainly through chemical syntheses. Meanwhile, phenanthroindolizidine alkaloids such as tylophorine and cuevaene A, diterpenes such as cafestol and kahweol, naphthoquinones such as JBIR‐76 and JBIR‐77, anagucycline C‐glycosides, and dodecahydrodibenzo[b,d]furan skeletons such as JBIR‐23 and JBIR‐24 have been isolated and found with different cytotoxic effects against several MPM cell lines. The present short review summarizes the synthetic strategies of these anti‐MPM molecules.

Photoredox Divergent 1,2-Difunctionalization of Alkenes with gem-Dibromides.

The redox neutral photocatalytic divergent radical 1,2-difunctionalization of a wide array of structurally varied alkenes with gem-dibromides is presented. On the basis of the electronic effect of alkenes, predictable 1,2-carboxygenation and 1,2-carbohalogenation of alkenes are readily available regardless of steric effect. This protocol affords a practical approach to the biologically important furan skeleton. It is distinguished by good regioselectivity, good functional group compatibility, and late-stage modification and thus signifies an important step forward to divergent radical difunctionalization of alkenes.

Nickel-Promoted Reductive Cyclization Cascade: A Short Synthesis of a New Aromatic Strigolactone Analogue

A stereospecific synthesis of the tetrahydro-2H-indeno[1,2-b]furan skeleton, which is embedded in bioactive aromatic strigolactones such as GR24, is realized by a nickel-mediated tandem cross-coupling for the first time. The observed cis-stereoselectivity during the intramolecular formation of the Csp3–Csp2 bond is rationalized through conformation analysis and DFT calculations.

Terphenyl Derivatives from Allantophomopsis lycopodina.

Three secondary fungal metabolites 1-3 with a benzo[b]naphtho[2,1-d]furan skeleton were isolated from submerged cultures of the ascomycete Allantophomopsis lycopodina. The NMR-based structure elucidation was challenging due to a low H/C ratio of only 0.64 and 0.68, respectively. NMR measurements in two different solvents and the use of NMR experiments such as HSQC-TOCSY and LR-HSQMBC proved to be helpful in this respect. The proposed structures obtained from the comprehensive analysis of the NMR data were verified by comparison of recorded and computed NMR chemical shifts from quantum chemical calculations of several constitutional isomers and were further analyzed with the aid of the DP4 and DP4+ probabilities.

1,3-Dipolar Cycloaddition in the Preparation of New Fused Heterocyclic Compounds via Thermal Initiation.

This paper describes the synthesis of precursors with a benzo[b]furan skeleton for the intramolecular 1,3-dipolar cycloaddition of azomethine ylides prepared from N-substituted 3-allyl-aminobenzo[b]furan-2-aldehydes and secondary amines derived from α-amino acid esters. Reactions were initiated by heating. The products consisted of four fused rings with three stereogenic centers. Their structure and stereochemistry were determined by NMR spectra and X-ray measurements.

ChemInform Abstract: Modular Synthesis of Multisubstituted Furans Through Palladium‐Catalyzed Three‐Component Condensation of Alkynylbenziodoxoles, Carboxylic Acids, and Imines.

Mild and regiocontrolled synthesis of a multisubstituted furan is achieved through Pd(OAc)2 -catalyzed room-temperature condensation of an alkynylbenziodoxole, a carboxylic acid, and an enolizable ketimine, which contribute to C1, CO, and C2 fragments, respectively, to the furan skeleton. The reaction tolerates a broad range of functional groups in each of the reaction components, and enables highly modular and flexible synthesis of variously substituted furans. The reaction is particularly effective for the rapid generation of tri- and tetraarylfurans and furan-containing oligoarylenes without relying on conventional cross-coupling chemistry.

Yb(OTf)3-Mediated Access to Furans from β-Ketothioamides via Eschenmoser Sulfide Contraction Reaction.

A mild and straightforward synthetic protocol for construction of a furan skeleton promoted by Yb(OTf)3 from β-ketothioamides and arylglyoxals has been developed at room temperature. Importantly, this protocol involves a tandem sequence that includes aldol condensation, N-cyclization, ring opening, O-cyclization, S-cyclization, and Eschenmoser sulfide contraction.

Modular synthesis of multisubstituted furans through palladium-catalyzed three-component condensation of alkynylbenziodoxoles, carboxylic acids, and imines.

Mild and regiocontrolled synthesis of a multisubstituted furan is achieved through Pd(OAc)2 -catalyzed room-temperature condensation of an alkynylbenziodoxole, a carboxylic acid, and an enolizable ketimine, which contribute to C1, CO, and C2 fragments, respectively, to the furan skeleton. The reaction tolerates a broad range of functional groups in each of the reaction components, and enables highly modular and flexible synthesis of variously substituted furans. The reaction is particularly effective for the rapid generation of tri- and tetraarylfurans and furan-containing oligoarylenes without relying on conventional cross-coupling chemistry.

Modular Synthesis of Multisubstituted Furans through Palladium‐Catalyzed Three‐Component Condensation of Alkynylbenziodoxoles, Carboxylic Acids, and Imines

AbstractMild and regiocontrolled synthesis of a multisubstituted furan is achieved through Pd(OAc)2‐catalyzed room‐temperature condensation of an alkynylbenziodoxole, a carboxylic acid, and an enolizable ketimine, which contribute to C1, CO, and C2 fragments, respectively, to the furan skeleton. The reaction tolerates a broad range of functional groups in each of the reaction components, and enables highly modular and flexible synthesis of variously substituted furans. The reaction is particularly effective for the rapid generation of tri‐ and tetraarylfurans and furan‐containing oligoarylenes without relying on conventional cross‐coupling chemistry.