PBCDD/F formation from radical/radical cross-condensation of 2-Chlorophenoxy with 2-Bromophenoxy, 2,4-Dichlorophenoxy with 2,4-Dibromophenoxy, and 2,4,6-Trichlorophenoxy with 2,4,6-Tribromophenoxy

Quantum chemical calculations were carried out to investigate the homogeneous gas-phase formation of mixed polybrominated/chlorinated dibenzo-p-dioxins/benzofurans (PBCDD/Fs) from the cross-condensation of 2-chlorophenoxy radical (2-CPR) with 2-bromophenoxy radical (2-BPR), 2,4-dichlorophenoxy radical (2,4-DCPR) with 2,4-dibromophenoxy radical (2,4-DBPR), and 2,4,6-trichlorophenoxy radical (2,4,6-TCPR) with 2,4,6-tribromophenoxy radical (2,4,6-TBPR). The geometrical parameters and vibrational frequencies were calculated at the MPWB1K/6-31+G(d,p) level, and single-point energy calculations were performed at the MPWB1K/6-311+G(3df,2p) level of theory. The rate constants of the crucial elementary reactions were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) correction over a wide temperature range of 600-1200K. Studies show that the substitution pattern of halogenated phenols not only determines the substitution pattern of the resulting PBCDD/Fs, but also has a significant influence on the formation mechanism of PBCDD/Fs, especially on the coupling of the halogenated phenoxy radicals.

From synthesis to function via iterative assembly of N-methyliminodiacetic acid boronate building blocks

The study and optimization of small molecule function is often impeded by the time-intensive and specialist-dependent process that is typically used to make such compounds. In contrast, general and automated platforms have been developed for making peptides, oligonucleotides, and increasingly oligosaccharides, where synthesis is simplified to iterative applications of the same reactions. Inspired by the way natural products are biosynthesized via the iterative assembly of a defined set of building blocks, we developed a platform for small molecule synthesis involving the iterative coupling of haloboronic acids protected as the corresponding N-methyliminodiacetic acid (MIDA) boronates. Here we summarize our efforts thus far to develop this platform into a generalized and automated approach for small molecule synthesis. We and others have employed this approach to access many polyene-based compounds, including the polyene motifs found in >75% of all polyene natural products. This platform further allowed us to derivatize amphotericin B, the powerful and resistance-evasive but also highly toxic last line of defense in treating systemic fungal infections, and thereby understand its mechanism of action. This synthesis-enabled mechanistic understanding has led us to develop less toxic derivatives currently under evaluation as improved antifungal agents. To access more Csp(3)-containing small molecules, we gained a stereocontrolled entry into chiral, non-racemic α-boryl aldehydes through the discovery of a chiral derivative of MIDA. These α-boryl aldehydes are versatile intermediates for the synthesis of many Csp(3) boronate building blocks that are otherwise difficult to access. In addition, we demonstrated the utility of these types of building blocks in accessing pharmaceutically relevant targets via an iterative Csp(3) cross-coupling cycle. We have further expanded the scope of the platform to include stereochemically complex macrocyclic and polycyclic molecules using a linear-to-cyclized strategy, in which Csp(3) boronate building blocks are iteratively assembled into linear precursors that are then cyclized into the cyclic frameworks found in many natural products and natural product-like structures. Enabled by the serendipitous discovery of a catch-and-release protocol for generally purifying MIDA boronate intermediates, the platform has been automated. The synthesis of 14 distinct classes of small molecules, including pharmaceuticals, materials components, and polycyclic natural products, has been achieved using this new synthesis machine. It is anticipated that the scope of small molecules accessible by this platform will continue to expand via further developments in building block synthesis, Csp(3) cross-coupling methodologies, and cyclization strategies. Achieving these goals will enable the more generalized synthesis of small molecules and thereby help shift the rate-limiting step in small molecule science from synthesis to function.

Design and synthesis of a potent inhibitor of class 1 DYRK kinases as a suppressor of adipogenesis

Dysregulation of dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) has been demonstrated in several pathological conditions, including Alzheimer's disease and cancer progression. It has been recently reported that a gain of function-mutation in the human DYRK1B gene exacerbates metabolic syndrome by enhancing obesity. In the previous study, we developed an inhibitor of DYRK family kinases (INDY) and demonstrated that INDY suppresses the pathological phenotypes induced by overexpression of DYRK1A or DYRK1B in cellular and animal models. In this study, we designed and synthesized a novel inhibitor of DYRK family kinases based on the crystal structure of the DYRK1A/INDY complex by replacing the phenol group of INDY with dibenzofuran to produce a derivative, named BINDY. This compound exhibited potent and selective inhibitory activity toward DYRK family kinases in an in vitro assay. Furthermore, treatment of 3T3-L1 pre-adipocytes with BINDY hampered adipogenesis by suppressing gene expression of the critical transcription factors PPARγ and C/EBPα. This study indicates the possibility of BINDY as a potential drug for metabolic syndrome.

Synthesis, Characterization and Thermal Decomposition Kinetics of a Novel Benzofuran Ketoxime Derived Polymer

A novel benzofuran ketoxime derived polymer, poly(benzofuran-2-yl-methylketoxime-O-methacrylate) [poly(BMKMA], was firstly synthesized by free radical polymerization method. Its thermal degradation studies were performed by thermogravimetric analysis (TGA) in order to determine the actual reaction mechanisms of the decomposition process. The activation energy of the solid-state process was determined using Flynn-Wall-Ozawa method, which resulted to be 235.94 kJ/mol. The activation energies of different mechanism models were determined by Coats-Redfern, Madhusudanan and Van Krevelen kinetic methods. Compared with the Ozawa method, the actual reaction mechanism obeyed deceleration type, phase boundary controlled reaction (R1).

Copper-Catalyzed Intramolecular Desymmetric Aryl C-O Coupling for the Enantioselective Construction of Chiral Dihydrobenzofurans and Dihydrobenzopyrans

O-Heterocyclic structures such as 2,3-dihydrobenzofurans are key motifs in many natural compounds and pharmaceuticals. Enantioselective formation of chiral dihydrobenzofurans and analogues was achieved through a copper-catalyzed desymmetrization strategy with a chiral cyclic 1,2-diamine. A broad range of substrates are compatible with this Cu(I)-diamine catalytic system and afford the desired coupling products with chiral tertiary or quaternary carbon centers in high yields and good to excellent enantioselectivities under mild conditions.

Synthesis and structural characterization of natural benzofuranoids

The synthesis of ustusoranes A, B, and E, pergillin, dihydropergillin, (±)-penicisochroman A, and (-)-brassicadiol, starting from optically active (R)-benzolactone, is described. The synthesis of ustusoranes A and E established the absolute configurations of these natural products. The synthesis of pergillin and (±)-penicisochroman A led to the structural revision of aspergiones E and F. This study clearly indicates that (R)-benzolactone is a potential intermediate in the synthesis of natural benzofuranoids.

Synthesis of a Functionalized Benzofuran as a Synthon for Salvianolic Acid C Analogues as Potential LDL Antioxidants

A palladium mediated synthesis of a common synthon for the syntheses of antioxidant analogues of naturally occurring salvianolic acids is presented. The synthetic route may be used to obtain analogues with a balanced lipophilicity/hydrophilicity which may result in potentially interesting LDL antioxidants for the prevention of cardiovascular diseases.

Syntheses of arnottin I and arnottin II

Short total syntheses of arnottin I and II were accomplished in 5 and 6 steps, respectively. A sesamol-benzyne cycloaddition with a 3-furyl-benzoate followed by regiospecific lactonization provided rapid, large-scale access to the core of arnottin I. Saponification of arnottin I and hypervalent iodide mediated spirocyclization provided an efficient and direct preparation of racemic arnottin II.

NEW HETEROCYCLIC OXIME ETHERS OF 1-(BENZOFURAN-2-YL)ETHAN- 1-ONE AND THEIR ANTIMICROBIAL ACTIVITY

In this study, some O-benzyl (benzofuran-2-yl)ethan-1-one ether oximes were synthesized starting from 2-acetylbenzofuran. The structure elucidation of the compounds was performed by IR, 1H-NMR and 13C-NMR spectra. Antimicrobial activities of the compounds were examined and notable activity was observed.

Biomimetic kinetic resolution: highly enantio- and diastereoselective transfer hydrogenation of aglain ketones to access flavagline natural products

We have previously reported asymmetric syntheses and absolute configuration assignments of the aglains (+)-ponapensin and (+)-elliptifoline and proposed a biosynthetic kinetic resolution process to produce enantiomeric rocaglamides and aglains. Herein, we report a biomimetic approach for the synthesis of enantiomerically enriched aglains and rocaglamides via kinetic resolution of a bridged ketone utilizing enantioselective transfer hydrogenation. The methodology has been employed to synthesize and confirm the absolute stereochemistries of the pyrimidone rocaglamides (+)-aglaiastatin and (-)-aglaroxin C. Additionally, the enantiomers and racemate of each metabolite were assayed for inhibition of the heat-shock response, cytotoxicity, and translation inhibition.

Pharmacological Potential of Tetrahydrofurano/Pyrano Quinoline and Benzo[b]furoindolyl Derivatives in Acute Inflammation, Pain and Oxidative Stress

OBJECTIVE

Investigation of the pharmacological potential of Tetrahydrofurano/pyrano quinoline and Benzo [b]furoindolyl derivatives in acute inflammation, pain and oxidative stress.

METHODS

Tetrahydrofurano/ pyrano quinoline and Benzo[b]furoindolyl were evaluated for anti-inflammatory activity by carrageenan-induced hind paw edema in rats. Analgesic activity in mice was assessed by both peripheral and central analgesic models. The free radical scavenging activity of the synthetic compound was analyzed by the in vivo antioxidant assays, by measuring the antioxidant enzymes such as Superoxide dismutase (SOD), Catalase and Peroxidase from the liver homogenate and the in vitro antioxidant activity was evaluated by DPPH photometric assay, Hydroxyl radical scavenging and Lipid Peroxidation assay.

RESULTS

The compounds had substantially inhibited the inflammation induced by subcutaneous carrageenan injection. The same compounds had demonstrated remarkable central and peripheral analgesic activity with potent free radical scavenging activity as evident from both in vitro and in vivo antioxidant assays.

CONCLUSION

Tetrahydrofurano/pyrano quinoline and Benzo[b]furoindolyl derivatives exhibit varied pharmacological activities that include anti-inflammatory, analgesic and antioxidant activity.

Formation of polybrominated dibenzofurans from polybrominated biphenyls

Decades after phasing out their production and use, especially in the formulations of brominated flame retardants (BFRs), polybrominated biphenyls (PBBs) still pose serious environmental and health problems. The oxidation of PBB has been hypothesised as a pathway for the formation of the notorious polybrominated dibenzofurans (PBDFs) and their dispersion in the environment. However, the exact reaction corridor remains misunderstood, with the existing mechanisms predicting the reaction to proceed via a high energy process that involves the breakage of C-C linkage (∼118.0 kcal mol(-1)) and the subsequent formation of bromophenols molecules, where the latter are supposed to act as precursors for the formation of PBDFs (∼40.0-60.0 kcal mol(-1)). Herein, we show that PBBs produce PBDFs in a facile mechanism through a series of highly exothermic reactions (i.e., overall barriers reside 8.2-10.0 kcal mol(-1) below the entrance channel). Whilst the fate of the ROO-type intermediates in oxidation of all aromatics is to emit CO or CO2, PBDFs constitute the dominant products from the oxidation of PBBs. Initially formed R-OO adduct evolves in a very exoergic mechanism to yield PBDFs. In view of the facile oxidative transformation of PBBs into PBDFs, we conclude that, it is unsafe to dispose BFRs in oxidation processes, as this practice generates high yields of toxic PBDFs.

Facile, protection-free, one-pot synthesis of aureusidin

A new, reliable, and convenient protection-free one-pot method for the synthesis of aureusidin (1) is described. The present synthetic approach involves the condensation of 4,6-dihydroxybenzofuranone with 3,4-dihydroxybenzaldehyde in the presence of concentrated HCl to afford aureusidin (1) in good yield with high purity. This procedure offers a short and simple route for the preparation of aureusidin (1), a bioactive natural product from several vegetal species, as well as for synthesis of other aurones.

Photocatalytic synthesis of dihydrobenzofurans by oxidative [3+2] cycloaddition of phenols

We report a protocol for oxidative [3+2] cycloadditions of phenols and alkenes applicable to the modular synthesis of a large family of dihydrobenzofuran natural products. Visible-light-activated transition metal photocatalysis enables the use of ammonium persulfate as an easily handled, benign terminal oxidant. The broad range of organic substrates that are readily oxidized by photoredox catalysis suggests that this strategy may be applicable to a variety of useful oxidative transformations.

Stereodivergent organocatalytic intramolecular Michael addition/lactonization for the asymmetric synthesis of substituted dihydrobenzofurans and tetrahydrofurans

A stereodivergent asymmetric Lewis base catalyzed Michael addition/lactonization of enone acids into substituted dihydrobenzofuran and tetrahydrofuran derivatives is reported. Commercially available (S)-(-)-tetramisole hydrochloride gives products with high syn diastereoselectivity in excellent enantioselectivity (up to 99:1 d.r.syn/anti , 99 % eesyn ), whereas using a cinchona alkaloid derived catalyst gives the corresponding anti-diastereoisomers as the major product (up to 10:90 d.r.syn/anti , 99 % eeanti ).

De novo synthesis of brominated dioxins and furans

On the basis of laboratory experiments with model mixtures (active carbon+CuBr2 at different loads), this work studies the formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) by de novo synthesis. For the different samples, the temperature of the maximum carbon oxidation rate was determined by thermogravimetric analysis, and a kinetic model was proposed for the degradation of the materials in an oxidizing atmosphere (synthetic air). The effect of the addition of different amounts of CuBr2 was studied, finding that its presence accelerates the degradation of the carbonaceous structure in the presence of oxygen. The thermal degradation of the samples in air is satisfactorily described by a first-order single-reaction model. In addition, combustion runs of one of the mixtures (consisting of activated carbon+50 wt % CuBr2, pyrolyzed at 700 °C) were performed in a quartz horizontal laboratory furnace. The analysis of the emissions and the solid residue proved the formation of brominated dioxins and furans at 300, 400, and 500 °C, with a maximum yield at 300 °C (91.7 ng/g of total PBDD/Fs) and a higher bromination degree with increasing temperature.

Synthesis and Absolute Configuration of (−)-3-Butyl-7-hydroxyphthalide, a Cytotoxic Metabolite ofPenicillium vulpinum*

Both the enantiomers as well as the racemate of 3-butyl-7-hydroxyphthalide (1) were synthesized, and the absolute configuration of the naturally occurring (-)-1 (a weakly cytotoxic metabolite of Penicillium vulpinum) was identified as S.

Synthesis and Antioxidative Activity of 3′,4′,6,7-Tetrahydroxyaurone, a Metabolite ofBidens frondosa

3',4',6,7-Tetrahydroxyaurone (1a), an aurone isolated from Bidens frondosa, and five analogues (1b-1f) were synthesized from pyrogallol in three steps. The antioxidative activity of 1a-1f was determined by the superoxide free radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging methods.

Remodeling natural products: chemistry and serine hydrolase activity of a rocaglate-derived β-lactone

Flavaglines are a class of natural products with potent insecticidal and anticancer activities. β-Lactones are a privileged structural motif found in both therapeutic agents and chemical probes. Herein, we report the synthesis, unexpected light-driven di-epimerization, and activity-based protein profiling of a novel rocaglate-derived β-lactone. In addition to in vitro inhibition of the serine hydrolases ABHD10 and ACOT1/2, the most potent β-lactone enantiomer was also found to inhibit these enzymes, as well as the serine peptidases CTSA and SCPEP1, in PC3 cells.

Semisynthesis and insecticidal activity of some fraxinellone derivatives modified in the B ring

A series of novel fraxinellone derivatives modified at the C-1 or C-8 position in the B ring were prepared as insecticidal agents against the pre-third-instar larvae of oriental armyworm, Mythimna separata Walker at 1 mg/mL. Five key steric configurations of compounds 2, 3, and 8f,g,j were further determined by single-crystal X-ray diffraction. It was found that the kinds and the amount of the reduction products of fraxinellone were related to the molar ratio between the reduction agent Red-Al and the substrate fraxinellone. Among all of the derivatives, compounds 2 and 8i,j,o displayed more promising insecticidal activity than their precursors fraxinellone and toosendanin. The preliminary structure-activity relationships revealed that the lactone (B-ring) of fraxinellone contributed to the observed insecticidal activity; the double bond at the C-2 position of fraxinellone was not necessary for the insecticidal activity; conversion of the oxygen atom of carbonyl group on the lactone of fraxinellone to a sulfur one does not improve the insecticidal activity; introduction of electron-withdrawing groups on the phenyl ring of 8f, to the benzoyloxy series, could result in more potent compounds.

One-pot synthesis, FT-IR and density functional method (DFT) studies on N-benzyl-N-ethyl-N-[5-nitro-2-(1,1,3,3-Tetramethylbutylamino)-1-benzofuran-3-yl]amine

N-benzyl-N-ethyl-N-[5-nitro-2-(1,1,3,3-Tetramethylbutylamino))-1-benzofuran-3-yl]amine, 7, was synthesized and characterized by elemental analysis, FT-IR, (1)H and (13)C NMR spectra. The geometrical structures, vibrational frequencies, and molecular electrostatic potential (MEP) of 7 in the ground state were calculated by using the DFT/B3LYP method with 6-31 G(d) basis set. The optimized structure was compared with analogous compound. The IR spectrum of 7 was interpreted in terms of potential energy distribution (PED) analysis. Comparison of the experimental vibrational spectra of 7 with the theoretical data indicated good agreement.

Rhodium-catalyzed tandem annulation and (5 + 1) cycloaddition: 3-hydroxy-1,4-enyne as the 5-carbon component

A Rh-catalyzed tandem annulation and (5 + 1) cycloaddition was realized. 3-Hydroxy-1,4-enyne served as the new 5-carbon component for the (5 + 1) cycloaddition. Substituted carbazoles, dibenzofurans, and tricyclic compounds containing a cyclohexadienone moiety could be prepared efficiently. The identification of a byproduct suggests that metal carbene and ketene intermediates may be involved in the (5 + 1) cycloaddition.

Synthesis and biological evaluation of benzofuroxan derivatives as fungicides against phytopathogenic fungi

Forty-four benzofuroxan derivatives were designed and prepared as antifungal agents. Their structures were characterized by (1)H NMR, (13)C NMR, and HRMS. Their antifungal activities were tested in vitro with four important phytopathogenic fungi, namely, Rhizoctonia solani , Sclerotinia sclerotiorum , Fusarium graminearum and Phytophthora capsici , using the mycelium growth inhibition method. Compound A5 displayed the maximum antifungal activity against F. graminearum (IC50 = 1.1 μg/mL, which is about 2-fold higher than that of the well-known positive control carbendazim (IC50 = 0.5 μg/mL). A14 exhibited high antifungal effect against both S. sclerotiorum and F. graminearum Sehw., with IC50 values of 2.52 and 3.42 μg/mL, respectively. Among 14 benzofuroxan derivatives with substitutions at the R(2) and R(3) positions of the phenyl ring (B series), 7 compounds displayed strong growth inhibition against R. solani (IC50 ≤ 3.0 μg/mL). Analysis of the structure-activity relationship data of these compounds revealed that (1) introduction of an electron-donating amino group to the R(2) position of the phenyl ring favors antifungal activity against R. solani and (2) the presence of a nitro group at the R(4) position and substituent variation at the R(1) position of the phenyl ring can result in good antifungal candidates against F. graminearum Sehw. Overall, the benzofuroxan was discovered as a novel scaffold for the development of fungicides. Significantly, A14 was demonstrated to successfully suppress disease development in S. sclerotiorum infected cole in vivo.

A recyclable palladium-catalyzed synthesis of 2-methylene-2,3-dihydrobenzofuran-3-ols by cycloisomerization of 2-(1-hydroxyprop-2-ynyl)phenols in ionic liquids

A recyclable palladium-catalyzed synthesis of 2-methylene-2,3-dihydrobenzofuran-3-ols 2 by heterocyclization of 2-(1-hydroxyprop-2-ynyl)phenols 1 in an ionic liquid medium (BmimBF4) is presented. The process takes place under relatively mild conditions (100 °C, 5 h) in the presence of catalytic amounts (2 mol %) of PdI2 in conjunction with KI (5 equiv with respect to PdI2) and an organic base, such as morpholine (1 equiv with respect to 1), to give 2 in high yields (70%-86%). The PdI2-KI catalytic system could be recycled up to six times without appreciable loss of activity. Moreover, products 2 could be easily converted in a one-pot fashion into 2-hydroxymethylbenzofurans 3 (52%-71%, based on 1) and 2-methoxymethylbenzofurans 4 (52%-80%, based on 1) by acid-catalyzed allylic isomerization or allylic nucleophilic substitution.

Effects of stereoisomerism on the crystallization behavior and optoelectrical properties of conjugated molecules

Three stereoisomers of DPP(TBFu)2 are separated and identified to investigate the effects of stereoisomerism on crystal structures and the optoelectrical properties. The crystal structures and FET mobility are sensitive to stereoisomers, in which the mesomer possesses the highest carrier mobility and the greatest crystallization tendency to dominate the crystallization in spin-cast films of the as-synthesized stereoisomeric mixture.