Furan Ring System Research Articles

Dicitrinols A-C: Citrinin Derivatives from Hydrothermal Vent-Associated Fungus Penicillium citrinum TW132-59.

Three new unusual citrinin derivatives with a unique 6/5/7/5 core, dicitrinols A-C (1-3, respectively), were isolated via the fermentation of hydrothermal vent-associated fungus Penicillium citrinum TW132-59. Their structures were unambiguously determined by nuclear magnetic resonance, mass spectrometry, and electronic circular dichroism calculations. Dicitrinols A-C represent a novel cage carbon skeleton with a decahydro-5,9,4-(epipropane[1,1,3]triyl)cycloocta[b]furan ring system. Dicitrinols A-C showed moderate antifungal activity against Candida albicans, Cryptococcus neoformans, and Fusarium oxysporum and antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii with minimum inhibitory concentrations ranging from 4 to 16 μg/mL.

Scale-Up of production of 5-hydroxymethylfurfural-rich adhesive precursors and structural features of humin side products

A batch reaction system (volume 1 L) for scaled-up production of 5-HMF-based adhesive precursor solutions from industrially available fructose syrup was developed. The stabilizing effect of sodium dithionite addition was demonstrated. With this system, no concentration steps are needed in the production of adhesive precursors for wood composite board production. The reaction system was optimized in a design of experiment approach to achieve good reaction conditions and to produce reaction solutions with 5-HMF concentrations appropriate for adhesive synthesis. Only three runs in the adjusted system are required to produce enough precursor for the synthesis of 10 kg of adhesive, thereby enabling the testing of the adhesive systems in particle board trials.Furthermore, the structure of humin side products from different reaction stages, formed from 5-HMF and byproducts by condensation, aldol-like reactions and attack on furan ring systems, was investigated. The data were compared to information from literature and possible elements of humin structures are proposed.

Synthesis of Novel C/D Ring Modified Bile Acids.

Bile acid receptors have been identified as important targets for the development of new therapeutics to treat various metabolic and inflammatory diseases. The synthesis of new bile acid analogues can help elucidate structure–activity relationships and define compounds that activate these receptors selectively. Towards this, access to large quantities of a chenodeoxycholic acid derivative bearing a C-12 methyl and a C-13 to C-14 double bond provided an interesting scaffold to investigate the chemical manipulation of the C/D ring junction in bile acids. The reactivity of this alkene substrate with various zinc carbenoid species showed that those generated using the Furukawa methodology achieved selective α-cyclopropanation, whereas those generated using the Shi methodology reacted in an unexpected manner giving rise to a rearranged skeleton whereby the C ring has undergone contraction to form a novel spiro–furan ring system. Further derivatization of the cyclopropanated steroid included O-7 oxidation and epimerization to afford new bile acid derivatives for biological evaluation.

Design and synthesis of C3-symmetric molecules containing oxepine and benzofuran moieties via Metathesis

• We demonstrated a simple synthetic strategy to assemble C 3 -symmetric star-shaped phenyl and triazine central core based oxepine and benzofuran derivatives. • The key steps involved are Claisen rearrangement, double-bond isomerization and cyclo-trimerization. • We introduced oxepine and furan ring systems in C 3 -symmetric star-shaped phenyl and triazine core derivatives using olefin metathesis. • We studied photophysical properties of prepared molecules by fluorescence spectroscopic data. We report a new synthetic strategy to C 3 -symmetric star-shaped phenyl and triazine central cores bearing oxepine and benzofuran ring systems. In this regard, we have explored the application of metathetic strategy to construct C 3 -symmetric molecules starting with commercially available p -hydroxy acetophenone and p -hydroxy benzonitrile through cyclotrimerization, double bond isomerization, and ring-closing metathesis as key steps. We also studied photophysical properties of these molecules by fluorescence spectroscopic data. All compounds except 1 and 2 exhibit strong fluorescence.

Fusopoltides B–E, new polyketides isolated from Fusarium solani B-18

Four new polyketides, fusopoltides B–E, were isolated, along with four known compounds, from Fusarium solani B-18 cultured on brown-rice. Fusopoltide B is a diastereomer of its co-isolated known compound, fusopoltide A, featuring a pentaleno[1,2-c]pyran ring system. Fusopoltide C and fusopoltides D–E are incorporated the first natural polyketides featured decahydro-pentaleno[1,2-c]pyran and pentaleno[1,2-c]furan ring systems, respectively. The structural assignments were established using comprehensive spectroscopic techniques, the modified Mosher's ester method, and electronic circular dichroism (ECD) calculations.

Metabolit Utama Metilripariokhromen-A, Senyawa Bioaktif dalam Daun Eupatorium Riparium Reg. dalam Urin Tikus Jantan

Metilripariokhromene-A (MRC) (1) adalah senyawa bioaktif yang diisolasi dari daun Eupatorium riparium Reg. hasil koleksi Taman Nasional G. Merapi. MRC diisolasi dari ekstrak kloroform daun dengan metoda bioassay (BST) guided isolation. MRC mempunyai efek diuretik, menurunkan tekanan darah, dan mengeluarkan mineral dari tubuh. Efek ini juga ditunjukan oleh furosemide yang secara klinis telah digunakan sebagai diuretik. MRC merupakan senyawa khromen yang mempunyai 2 gugus –OCH3 pada cincin aromatiknya, secara in vivo kemungkinan mengalami demetilasi memberikan gugus fenolik (-OH) yang bersifat antiseptik. Penelitian ini dimaksudkan untuk mengetahui efek diuretik dibandingkan dengan furosemide, mengisolasi dan mengidentifikasi metabolit utama yang terdapat dalam urin, dan kemungkinan MRC dapat digunakan sebagai obat anti-infeksi pada saluran kemih. Ekstrak n-hexana (81% MRC) (1,25 g/Kg BW) secara per oral diberikan kepada tikus jantan (+ 200 g), dan furosemide juga diberikan sebagai kontrol positif untuk diuretik. Urin selama 48 jam dikumpulkan, dipartisi dengan EtOAc selama 15 menit sehingga diperoleh fraksi EtOAc. Fraksi EtOAc difraksinasi, dan metabolit utama yang terdapat dalam fr. 4-5, dan fr. 6-7 dipisahkan dengan KLT preparatif. Identifikasi struktur kimia metabolit utama dilakukan berdasarkan atas data 1H- dan 13C-NMR. Efek diuretik dari ekstrak n-heksana (1,25 g / kg bb) sebanding dengan furosemid (8,83 mL/ tikus vs 8,70 mL/ tikus selama 24 jam). Data 1H- dan 13C-NMR dari fr 4-5 menunjukkan bahwa tidak ada perubahan besar dalam penampilan spektrum 1H- dan 13C-NMR dibandingkan dengan MRC, kecuali bahwa gugus 1 -OCH3 didemetilasi menjadi demetil MRC (2) . Berdasarkan eksperimen HMBC dan HMQC, -OCH3 di C-8 adalah yang demetilasi. Data 1H-NMR dari fr. 6-7 mirip dengan fr. 4-5, demetilasi satu-OCH3 grup pada C-8 tetapi hubungan eter dalam sistem ring furan rusak untuk memberikan 2 struktur tentatif (3 dan 4).

2,5‐Diamide‐Substituted Five‐Membered Heterocycles: Challenging Molecular Synthons

AbstractWe describe synthetic routes for preparing previously unknown 2,5‐diamide‐substituted five‐membered heterocycles based on the thiophene, pyrrole, and furan ring systems by exploiting Curtius‐like rearrangement reactions. Conformation analysis of the 2,5‐diamidothiophene derivatives identified a “closed” conformation, in which the two carbonyl O atoms are in close contact with the thiophene S atom.

Synthesis of 1‐Arylnaphthalenes by Gold‐Catalyzed One‐Pot Sequential Epoxide to Carbonyl Rearrangement and Cyclization with Arylalkynes

Intermolecular and intramolecular reactions of a one-pot gold-catalyzed epoxide rearrangement followed by an electrophilic addition to arylalkynes to synthesize 1-arylnaphthalenes have been reported. The intramolecular reaction has been applied to synthesize 1-arylnaphthalenes fused with saturated furan, pyran, pyrrole, and cyclopentane ring systems.

Derivatives of benzo[b]furan. Part I. Conformational studies of khellinone and visnaginone

The structural analysis of khellinone and visnaginone indicated the planarity of the benzo[b]furan ring system. The oxygen or carbon atoms of the substituents, –OH, –OCH3, and –C(=O)CH3, are nearly coplanar with the aromatic ring. The molecular conformation is stabilized by the intramolecular O–H···O hydrogen bond formed between the ortho-substituted hydroxyl and acetyl groups. The intermolecular contacts present in the crystal structure are the C–H···O and C–H···π interactions and the π··· π stacking. The energy surface for the internal rotation about the Csp2–O/C bonds in the khellinone and visnaginone molecules has been explored by quantum-chemical calculations. The density functional theory (DFT) methods yielded three stable conformers of khellinone and two of visnaginone obtained by a rotation of the methoxy group about the C4sp2–OCH3 bond. The most stable conformation in the gas phase is consistent with the stereochemistry of the molecules adopted in the solid. The secondary minima conformers have energies higher by 0.3–1.8 kcal/mol. The energy of the intramolecular O–H···O interactions, present in the molecular structure of all stable conformers, is around 18 kcal/mol at the DFT level. A complete and reliable assignment of the bands in the IR and Raman spectra of both compounds has been performed.

Absorption and Metabolism of cis‐9,trans‐11‐CLA and of Its Oxidation Product 9,11‐Furan Fatty Acid by Caco‐2 Cells

Furan fatty acids (furan-FA) can be formed by auto-oxidation of conjugated linoleic acids (CLA) and may therefore be ingested when CLA-containing foodstuff is consumed. Due to the presence of a furan ring structure, furan-FA may have toxic properties, however, these substances are toxicologically not well characterized so far. Here we show that 9,11-furan-FA, the oxidation product of the major CLA isomer cis-9,trans-11-CLA (c9,t11-CLA), is not toxic to human intestinal Caco-2 cells up to a level of 100 μM. Oil-Red-O staining indicated that 9,11-furan-FA as well as c9,t11-CLA and linoleic acid are taken up by the cells and stored in the form of triglycerides in lipid droplets. Chemical analysis of total cellular lipids revealed that 9,11-furan-FA is partially elongated probably by the enzymatic activity of cellular fatty acid elongases whereas c9,t11-CLA is partially converted to other isomers such as c9,c11-CLA or t9,t11-CLA. In the case of 9,11-furan-FA, there is no indication for any modification or activation of the furan ring system. From these results, we conclude that 9,11-furan-FA has no properties of toxicological relevance at least for Caco-2 cells which serve as a model for enterocytes of the human small intestine.

N′-[(E)-(3-Phenyl-1H-pyrazol-4-yl)methylidene]naphtho[2,1-b]furan-2-carbohydrazide monohydrate

In the title hydrate, C23H16N4O2·H2O, the pyrazole ring is approximately planar, with a maximum deviation of 0.023 (1) Å, and makes dihedral angles of 28.63 (6) and 46.44 (7)° with the naphtho­[2,1-b]furan ring system and the benzene ring, respectively, In the crystal, O—H⋯N, O—H⋯O, N—H⋯O, N—H⋯N, C—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules, forming sheets lying parallel to the ab plane. The crystal structure also features C—H⋯π inter­actions involving the centroids of the pyrazole and benzene rings.

ChemInform Abstract: A New Approach to Fused Furan Ring Systems and Benzofurans: Intramolecular Cyclization Reactions of Unsaturated Acyloxy Sulfone Derivatives.

AbstractThe LiN(Tms)2‐mediated intramolecular cyclization is followed by TosOH‐catalyzed dehydration and double bond isomerization.

Intramolecular Cyclization of Acyloxy Sulfones to Fused Furans and Benzofurans

Reported is the synthesis of fused furan and benzofuran ring systems through an ­intramolecular cyclization of unsaturated acyloxy sulfone derivatives. Thus, exposure of allylic or benzylic sulfones to LHMDS leads to acyl group transfer to form intermediates, which upon an acid-promoted cyclization-dehydration sequence afford stable heteroaromatic ring systems. A narrow investigation of the substrate scope revealed that, although both allylic and phenolic esters perform well in this process, the latter required elevated temperature to progress to completion. In addition, the synthesis of two fused pyrans was demonstrated using the same procedure.

A new approach to fused furan ring systems and benzofurans: intramolecular cyclization reactions of unsaturated acyloxy sulfone derivatives

Unsaturated acyloxy sulfones 3 undergo intramolecular cyclization upon deprotonation with LHMDS in THF. Dehydration and double bond isomerization of the products upon exposure to acid, gave the fused ring furans, 4, in good yields. This strategy could be readily adapted to prepare substituted benzofurans 12 from the cyclization reactions of acyloxy sulfones 11 prepared from phenols. Finally, this approach could be successfully modified to access dihydropyrans and benzopyrans.

アレニルエーテルの分子内 Diels-Alder 反応による三環性フラン環骨格の構築

アレニルエーテルの分子内 Diels-Alder 反応による三環性フラン環骨格の構築

ChemInform Abstract: The Synthesis and Some Chemical Reactions of a 5a-Methyl-2H-naphtho(1, 8-bc)furan.

A synthesis of the tricycle 19 has been completed in 14% overall yield from guaiacol. Several chemical transformations of this compound including its reduction to an octahydro naphtho[1,8-bc]furan and conversion to the hitherto unknown azuleno-[8,1-bc]furan ring system are described.

ChemInform Abstract: Diastereoselective Synthesis of Spongian Diterpenes. Total Synthesis of the Furanoditerpene (-)-Spongia-13(16),14-diene.

Abstract An effective diastereoselective synthesis of the marine-sponge metabolite (−)-spongia-13(16),14-diene 1 is achieved starting from S-(+)-carvone via a homochiral phenanthrenone as the key intermediate for the construction of the furan ring system. S-(+)-Carvone was transformed into the phenanthrenone 2a in six steps (53% overall yield), using an intramolecular Diels-Alder reaction as the key step. Conversion of the enone function in 2a into an epoxyaldehyde function followed by cyclisation and aromatisation in acid conditions completed the construction of ring D.

(E)-3-(Anthracen-9-yl)-1-(furan-2-yl)prop-2-en-1-one

In the mol­ecule of the title heteroaryl chalcone derivative, C21H14O2, the almost planar prop-2-en-1-one unit [r.m.s. deviation = 0.0087 (1) Å] forms dihedral angles of 5.81 (7) and 49.85 (6)°, respectively, with the furan ring and anthracene ring system. In the crystal structure, the mol­ecules are linked into a two-dimensional network parallel to (100) by C—H⋯O hydrogen bonds and π⋯π inter­actions involving the furan rings [centroid–centroid distance = 3.7205 (6) Å].

Stereoselective synthesis of optically active cyclopenta[ c]pyrans and cyclopenta[ c]furans by the intramolecular Pauson–Khand reaction

An intramolecular Pauson–Khand reaction of enynes derived from homoallyl, homopropargyl, and allyl alcohols is described. 2-Heteroaryl-substituted homoallyl, homopropargyl, and allyl alcohols are easily and efficiently resolved through enzymatic resolution in high ee (91–99%) and with a known stereochemistry. Each enantiomerically enriched enyne derived from homoallyl and homopropargyl alcohols affords the conformationally most stable diastereomeric cyclopenta[ c]pyran ring system as the sole product, whereas enantiomerically enriched enynes derived from allyl alcohols give a diastereomeric cis: trans mixture of the cyclopenta[ c]furan ring system.

Synthesis and Bioactivity of Novel N,N′‐Diacylhydrazine Derivatives Containing Furan(I)

AbstractThe furan ring system possesses electron‐rich properties and exhibits various biological activities, which was introduced into diacylhydrazine to create novel leading compounds that may serve as improved pesticides and pharmaceuticals. A series of novel diacylhydrazine derivatives containing a furan ring were synthesized by the reaction of 5‐fluorophenyl‐2‐furoyl chloride with substituted benzoylhydrazide in anhydrous dichloromethane under reflux. The structures of the resultant compounds were confirmed by IR, 1H NMR, MS and elemental analysis. Insecticidal and anti‐tumor activities of these new compounds were evaluated.