Terminal Double Bond Research Articles

C-13 Norisoprenoids and Eudesmanoids from Nelumbo nucifera Gaertn. Regulate the Lipid Metabolism via the AMPK/ACC/SREBP-1c Signaling Pathway.

Lotustine A (1), an undescribed C-13 norisoprenoid, along with 22 known analogues and two eudesmanoids, were isolated from the aerial parts of Nelumbo nucifera Gaertn. Among them, compounds 2, 15, 17, 21, 22, 24, 25 were isolated from N. nucifera leaves for the first time. Their structures, including absolute configurations, were elucidated by nuclear magnetic resonance, mass spectroscopy, and the modified Mosher's method. Compound 1 is the first example of C-13 norisoprenoid with a terminal double bond between C-5 and C-13. Moreover, the lipid-lowering activities of the isolates were evaluated, and the results showed that 2, 24 and 25 could remarkably decrease the levels of both total cholesterol and triglyceride in free fatty acids induced HepG2 cells at the concentration of 20 μM. The oil red staining assay further demonstrated the lipid-lowering effects of 2, 24 and 25. The western blot results indicated that compounds 2, 24 and 25 could regulate the lipid metabolism via the activation of the AMPK/ACC/SREBP-1c signaling pathway.

Kinetic Investigation of the Emulsion Polymerization of Vinylidene Fluoride

AbstractPoly(vinylidene fluoride) (PVDF) is among the most produced fluoropolymers, second only to polytetrafluoroethylene. Despite its popularity, the complex microstructural properties achieved during the polymerization are not well documented in the literature. In particular, available models only track the chain length distribution of the polymer, while neglecting the distribution of other important properties, affecting the final behavior of the product. In this work, a 2D kinetic model, evaluating not only the chain length but also the number of terminal double bonds (TDBs) per chain, is developed. The numerical solution of the model is achieved by fractionating the population of polymer chains into classes with a specific number of TDBs and using the method of moments for each class. The model results are compared with experimental evidences for the amount of produced polymer, moles of main chain‐ends, number, and weight average molecular weight as well as full molecular weight distribution. Based on this comparison, kinetic parameters are estimated by optimization using genetic algorithm. The model reliability is finally verified using additional experimental data at different temperatures and amounts of initiator.

Hypecotumines A-D, new isoquinoline alkaloids with potential PCSK9 inhibition activity from Hypecoum erectum L.

Four new isoquinoline alkaloids, hypecotumines A-D (1-4), were isolated and identified from the whole herbs of Hypecoum erectum L. Their structures were determined by a combination of HRESIMS, NMR, and X-ray diffraction analysis methods. Compounds 1-4 were characterized by a terminal double bond at C-9 and their plausible biosynthetic pathway was hypothesized. Since PCSK9 plays a key role in the development of cardiovascular disease (CVD), exploration of PCSK inhibitors from natural products are beneficial for drug discovery of CVD treatment. SPR and Western blot assays showed compound 4 had PCSK9 inhibition activity with KD value of 59.9µM and thus elevated the LDLR level. Further molecular docking studies demonstrated that 4 and PCSK9 could form stable interactions via key hydrogen bonds.

Some Terminally Alkenyl-substituted Porphyrins: Synthesis and Attempts of Heck Reaction Leading to Porphyrin–Azulene Dyads

: The synthesis of meso-tetraphenylporphyrin derivatives, double functionalized in one of the phenyl rings (with a nitro group and carbon substituents), is described. 5-(4- Nitroaryl)-10,15,20-triarylporphyrinates react, in the presence of a base (t-BuOK), with carbanions containing a leaving group at the carbanionic center to give products of substitution of hydrogen at ortho-position to the nitro group via vicarious nucleophilic substitution scheme. Their alkylation with allyl bromide or 4-bromobut-1-en (t-BuOK/DMF, at 0-5°C) leads to porphyrins bearing side alkyl chain with a terminal double bond in yields of up to 82%. The above-mentioned double-substituted intermediates are very convenient substrates for Heck cross-coupling reaction. In this study, the synthesis of porphyrin–azulene dyads is reported. In some cases, the formation of highly conjugated systems is observed, with moderate yield. Their structures are interesting from both the porphyrin and azulene point of view.

Chemistry of ruthenium complexes with hexamethylbenzene and butadienesulfonyl ligands: Synthesis and reactivity toward phosphites and silver triflate

The addition reaction of (η6-C6Me6)Ru(Cl)(1-2,5-η-CH2CHCHCHSO2) (1) with one equivalent of P(OMe)3 or P(OPh)3 led to the formation of the corresponding compounds (η6-C6Me6)Ru(Cl)(5-η-SO2CHCHCHCH2)(P(OR)3) (R = Me, 4a; Ph, 4b). After 4a and 4b lose AgCl in presence of AgOTf, the immediate coordination of the terminal double bond of the butadienesulfonyl ligand affords the corresponding cationic complexes [(η6-C6Me6)Ru(1-2,5-η-CH2CHCHCHSO2)(P(OR)3]OTf (R = Me, 5a; Ph, 5b). The alternative metathesis reaction between dichlorido compounds (η6-C6Me6)Ru(Cl)2(P(OR)3) (R = Me, 2a, Ph, 2b) and the potassium butadiene sulfinate K(SO2CHCHCHCH2) (3) was only successful in the case of 4a. The 1H, 13C{1H} NMR data of 4a and 4b are consistent with a butadienesulfonyl ligand coordinated preferentially as an S conformer, while only traces of the thermodynamic W conformer have been seen in solution for 4a. The single crystal analysis of neutral 4a and cationic 5b reveals the presence of the butadienesulfonyl ligand binding to ruthenium exclusively through the sulfur atom in the case of 4a, while in 5b, the coordination of the terminal double bond to the metal center also occurs. A comparative study of the influence of the phosphite and phosphine ligands on analogue isoelectronic molecular structures with the η6-C6Me6 and η5-C5Me5 anchored ligands is analyzed. The high stability of 2a and 2b is corroborated and compared to the phosphine analogues. The single crystal of 2b is also discussed.

Selective Cleavage of α-Olefins to Produce Acetylene and Hydrogen.

Acetylene production from mixed α-olefins emerges as a potentially green and energy-efficient approach with significant scientific value in the selective cleavage of C-C bonds. On the Pd(100) surface, it is experimentally revealed that C2 to C4 α-olefins undergo selective thermal cleavage to form surface acetylene and hydrogen. The high selectivity toward acetylene is attributed to the 4-fold hollow sites which are adept at severing the terminal double bonds in α-olefins to produce acetylene. A challenge arises, however, because acetylene tends to stay at the Pd(100) surface. By using the surface alloying methodology with alien Au, the surface Pd d-band center has been successfully shifted away from the Fermi level to release surface-generated acetylene from α-olefins as a gaseous product. Our study actually provides a technological strategy to economically produce acetylene and hydrogen from α-olefins.

Dirhodium(II)/DPPM Catalyzed 1,2-Hydrosilylation of Conjugated Dienes with Tertiary Silanes.

A simple and efficient Rh2(OAc)4/DPPM (bis(diphenylphosphanyl)methane) catalyzed regioselective 1,2-anti-Markovnikov hydrosilylation of conjugated dienes with various tertiary silanes gave homoallylic silanes in acetonitrile, which tolerate broad functional groups. Control experiments proved that no π-allyl transition metal intermediates were involved in this 1,2-anti-Markovnikov hydrosilylation. Dirhodium hydride species was observed in hydrosilylation, suggesting that a direct insertion of the terminal double bond into a Rh-H bond is involved in this reaction.

Synchronous and zwitter-ion channels of (<i>R</i>)-5-methyl2-(1-methylethylidene)-cyclohexanone reaction with 4-phenyl-4<i>H</i>-1,2,4-triazoline-3,5-dione

The interaction of pulegone with enophil - 4-phenyl-4 H -1,2,4-triazoline-3,5-dione leads to the formation of two described earlier epimers: 1-[(1 R ,4 R )-4-methyl-1-(1-methylethenyl)-2-oxocyclohexyl]-4-phenyl-1,2,4-triazolidine-3,5-dione ( RR -isomer) and 1-[(1 S ,4 R )-4-methyl-1-(1-methylethenyl)-2-oxocyclohexyl]-4-phenyl-1,2,4-triazolidine-3,5-dione ( SR -isomer). Along with these epimers, we found another isomer - 1-{1-methyl-1-[(4 R )-4methyl-6-oxocyclohex-1-en-1-yl]ethyl}-4-phenyl-1,2,4-triazolidine-3,5-dione. Quantum chemical modeling has established that isomeric products of hydrogen substitution in pulegone by enophil are formed along three routes. In the SR -isomer formation route, the ene reaction proceeds consistently. The other two routes are implemented with the enophil approach from the R -side of the pulegon. These routes consist of two consecutive stages. At the first stage, an intermediate of the type of asymmetric cyclic aziridine cation is formed. Elimination of a proton from one of the geminal methyl groups of the intermediate leads to an RR -isomer with a terminal double bond. When a proton is eliminated from the methylene group of the pulegog ring, an internal unsaturated compound is formed. The ratio of the yield of the isomer with an internal double binding and the RR -isomer depends on the polarity of the aprotic solvents.

The Use of High‐Temperature Semi‐Batch Radical Polymerization to Synthesize Acrylate Based Macromonomers and Structured Copolymers

AbstractA high‐temperature starved‐feed semi‐batch operating policy is developed to produce p(acrylates) with high macromonomer content, taking advantage of side reactions inherent to acrylate radical polymerization. This operating strategy results in significantly higher macromonomer content for the polymerization of isobornyl acrylate (iBoA) versus n‐butyl acrylate (BA) under identical operating conditions. This is because steric hindrance favors fragmentation (i.e., terminal double bond (TDB) formation) over addition (i.e., short‐chain or long‐chain branch (LCB) formation), thus increasing the p(iBoA) TDB content and decreasing polymer dispersity. The p(iBoA) macromonomer solution serves as an excellent addition‐fragmentation agent to polymerize a second monomer in a single pot process controlled by sequential feeding, as demonstrates by the production of iBoA‐BA block and comb copolymer structures at different temperatures and macromonomer concentrations. The incorporation of the p(iBoA) macromonomer into a copolymer product is verified by various techniques, including polymer fractionation followed by TDB, composition, and molar mass analyses. Reaction temperature plays a key role in determining whether a blocky versus comb copolymer structure is produced. The ability to synthesize block and comb copolymers by radical polymerization without a mediating agent offers the potential to efficiently produce structured copolymers for industrial applications.

Design and Investigation of a Side-Chain Liquid Crystalline Polysiloxane with a Ntb-Phase-Forming Side Chain

A new mesogenic non-symmetric dimeric monomer with a terminal olefin function, forming a twist bend nematic (Ntb) as well as a nematic (N) phase, was synthesized, using an enhanced synthetic methodology, which avoids isomerization of the terminal double bond in the preparation of the dimer. This monomer was attached to a pentamethyldisiloxane group, resulting in the SmA LC phase behavior of the ensuing material. Linking the monomer to a siloxane main chain resulted in nematic phase behavior. Detailed studies with the Ntb phase forming dimer DTC5C7 show full miscibility of the dimer and the new LC polymer in the LC state, suggesting that the side-chain LC polymer forms a Ntb phase as the low-temperature nematic phase. Copolymerizing the monomer with a cyanobiphenyl-based monomer allows us to tune the glass transition and phase behavior further.

Non-isocyanate polyurethanes synthesized from terpenes using thiourea organocatalysis and thiol-ene-chemistry

The depletion of fossil resources as well as environmental concerns contribute to an increasing focus on finding more sustainable approaches for the synthesis of polymeric materials. In this work, a synthesis route towards non-isocyanate polyurethanes (NIPUs) using renewable starting materials is presented. Based on the terpenes limonene and carvone as renewable resources, five-membered cyclic carbonates are synthesized and ring-opened with allylamine, using thiourea compounds as benign and efficient organocatalysts. Thus, five renewable AA monomers are obtained, bearing one or two urethane units. Taking advantage of the terminal double bonds of these AA monomers, step-growth thiol-ene polymerization is performed using different dithiols, to yield NIPUs with molecular weights of above 10 kDa under mild conditions. Variation of the dithiol and amine leads to polymers with different properties, with Mn of up to 31 kDa and Tg’s ranging from 1 to 29 °C.

Green Synthesis of UV-Reactive Polycarbonates from Levoglucosenone and 5-Hydroxymethyl Furfural.

This study focuses on the synthesis of fully renewable polycarbonates (PCs) starting from cellulose-based platform molecules levoglucosenone (LGO) and 2,5-bis(hydroxymethyl)furan (BHMF). These unique bio-based PCs are obtained through the reaction of a citronellol-containing triol (Triol-citro) derived from LGO, with a dimethyl carbonate derivative of BHMF (BHMF-DC). Solvent-free polymerizations are targeted to minimize waste generation and promote an eco-friendly approach with a favorable environmental factor (E-factor). The choice of metal catalyst during polymerization significantly influences the polymer properties, resulting in high molecular weight (up to 755kDa) when Na2 CO3 is employed as an inexpensive catalyst. Characterization using nuclear magnetic resonance confirms the successful incorporation of the furan ring and the retention of the terminal double bond of the citronellol pendant chain. Furthermore, under UV irradiation, the presence of both citronellol and furanic moieties induces singular structural changes, triggering the formation of three distinct structures within the polymer network, a phenomenon herein occurs for the first time in this type of polymer. These findings pave the way to new functional materials prepared from renewable monomers with tunable properties.

SYNTHESIS OF NEW POLYFUNCTIONAL CYCLIC KETALS BASED ON SUBSTITUTED 4-METHYLENE-1,3-DIOXOLANES

Methods for the preparation of new polyfunctional heterocyclic compounds based on the addition dichlorocarbene and ethanol to the terminal double bond of 2,2-disubstituted 4-methylene-1,3-dioxolanes, as well as on hydrogenation and ozonolysis of this bond, are proposed.

Isomerization-Free Matteson Homologations of Substituted Allylboronic Esters.

Substituted allyl derivatives with an internal double bond can be homologated under standard conditions via a 1,2-shift, whereas allylboronic esters with terminal double bonds can also be homologated via a SN' reaction. This allyl isomerization is catalyzed by ZnCl2 and can be suppressed by omitting ZnCl2 during the formation of α-chloroboronic ester. However, in the second step with Grignard reagents, ZnCl2 was added to suppress side reactions of the product formed.

Conversion of Unsaturated Short- to Medium-Chain Fatty Acids by Unspecific Peroxygenases (UPOs)

Eighteen short- to medium-chain monounsaturated fatty acids were screened for hydroxylation and epoxidation using eleven different peroxygenase preparations. Most of these unspecific peroxygenases (UPOs) are secreted by fungal species of the dark-spored basidiomycetous families Psathyrellaceae and Strophariaceae, two belonged to the white-spored genus Marasmius (Marasmiaceae), and one belonged to the ascomycetous family Chaetomiaceae. The fatty acids (FAs) studied were categorized into three groups based on the position of the double bond: (i) terminal unsaturated FAs (between ω and ω-1), (ii) α-β-unsaturated FAs (between C2 and C3), and (iii) β-γ-unsaturated FAs (between C3 and C4). Their chain lengths ranged from three to nine carbon atoms. FAs with a terminal double bond were significantly oxidized by only two UPOs, namely CglUPO and CraUPO (peroxygenases from Chaetomium globosum and Coprinellus radians, respectively), producing different products. FAs with internal double bonds were converted by all tested UPOs. While epoxides were observed as products in the case of α-β-unsaturated fatty acids, only CglUPO formed β-γ-epoxides from the corresponding FAs. The product pattern of the other UPOs for β-γ-unsaturated FAs was quite similar. On the other hand, the product pattern for oxidized α-β-unsaturated FAs was more variable and, in some cases, specific to a particular UPO. For example, in the reaction with trans-2-nonenoic acid, the enzymes clustered into six groups based on the formed products.

Interaction of O- and P- nucleophiles with perfluorinated olefins: Novel synthetic route to fluorinated phosphorus-containing monomers

A novel synthetic method for the preparation of partially fluorinated unsaturated diethyl phosphonates and phosphonic acids is presented involving the deprotonation of the starting α-hydroxymethyl diethylphosphonate or diethylphosphite with a strong base, followed by in situ addition of an O- or P-nucleophile to the terminal double bond of the perfluorinated olefin. Subsequent elimination of the corresponding leaving groups and restoring of the double bond leads to the target bifunctional perfluorinated olefins. Reaction of the diethyl phosphonate group with trimethylsilyl bromide (TMS-Br) and subsequent hydrolysis/methanolysis gave the corresponding unsaturated phosphonic acids. In the case of using α-hydroxymethyl diethylphosphonate, the reaction may be accompanied by an addition of a second equivalent of an O-nucleophile to form bis-functional internal olefins. The reaction conditions, factors affecting the reactivity, stereo- and regioselectivity of the process, the choice of reagent as well as the course of competitive reactions are discussed, too.

An Oligomer with Terminal Unsaturated Double Bonds Based on Epidian 5 and Ethylacrylic Acid

An oligomer with terminal unsaturated double bonds (unsaturated oligomer, UO) has been synthesized from epoxy resin Epidian 5 and ethylacrylic acid. The impact of the catalyst nature, temperature, and reaction duration on the progress of the reaction between the resin and the acid has been studied. A synthetic technique is proposed for producing the UO. The UO has been characterized by chemical and FTIR-spectroscopic analyses. The UO has been examined in the cross-linking processes with oligoesteracrylates TGM 3 and MGP 9 as well as unsaturated polyester PE 246. In order to prepare structurally colored films, unsaturated azo dyes have been additionally used. A mixture of cumene hy-droperoxide and cobalt naphthenate dissolved in styrene has been utilized as an initiating system for the cross-linking of the formulations. By using FTIR-spectroscopy, the chemistry of the development of the cross-linked structures of the oligoester mixtures in the presence of the UO has been revealed.

Direct Hydrodefluorination of CF3-Alkenes via a Mild SN2′ Process Using Rongalite as a Masked Proton Reagent

A concise and efficient hydrodefluorination process was developed for the synthesis of gem-difluoroalkenes. This reaction employs rongalite as a masked proton source and does not require any additional catalysts or reductants. Notably, trifluoromethyl alkenes having both terminal and internal double bonds are compatible with this process, allowing for a wider range of substrates. The successful late-stage functionalizations of pharmaceuticals and gram-scale syntheses were used to demonstrate the viability of this method.

Stelleratenoids A−F, macrocyclic daphnane orthoesters with anti-HIV activity from the roots of Stellera chamaejasme L.

Six undescribed macrocyclic daphnane orthoesters, stelleratenoids A−F (1−6), were isolated from the roots of Stellera chamaejasme L. Their structures were elucidated by extensive spectroscopic analyses, including HRESIMS and NMR spectra. Compound 1 features an unusual terminal double bond at C-2/C-19 in the 1α-alkyldaphnane lactone skeleton. Compounds 2−4 are unique in the presence of different long chain fatty acyl groups. Compounds 5 and 6 are unique examples of modified macrocyclic daphnane diterpenoids. All the isolates were evaluated for anti-HIV activity in MT-2 cells. Among them, compounds 1, 5 and 6 exhibited highly potent anti-HIV activity with EC50 values of 66.70, 10.62 and 55.10 nM, respectively, possessing high potential to develop new anti-HIV drugs.

Validation of an Extended Kinetic Model of Free‐RadicalN‐Vinylpyrrolidone Polymerization

AbstractTo predict the polymer properties produced by free‐radical polymerization ofN‐vinylpyrrolidone (NVP) in aqueous solution a detailed kinetic model has been developed. The kinetic model allows to calculate the chain length distribution, the number of branching points, and the number of terminal double bonds (TDB). The latter is accounted for since TDBs are a precondition for branching. While monomer conversion can be predicted sufficiently using independently determined rate constants for propagation and termination, here the predictions of structural properties by a newly developed extended kinetic model to experimental findings are compared. Polymer produced in a continuous stirred tank reactor is analyzed by gel permeation chromatography (GPC), field flow fractionation (FFF), and high‐pressure liquid chromatography (HPLC).