Vinyl Esters Research Articles

Cyanocobalamin (VB12) Bionic Enzyme-Assisted Photocatalytic Chain-Growth Polymerization for Detection of Lung Cancer Biomarkers.

Cobalt-mediated radical polymerization is noted for its great level of control over the polymerization of acrylic and vinyl esters monomers, even at high molar mass. Vitamin B12, a natural bionic enzyme cobalt complex, involves the conversion of organic halides to olefins through chain-growth polymerization. In this work, the notion of R-Co(III) free radical persistent free radical effect and vitamin B12 circulation were first reported for the perception of ultralow abundance of microRNA-21, a lung cancer biomarker. Indeed, most Co-containing catalytic reactions can occur under mild conditions due to their minimal bond dissociation of the C-Co bond, with blue light irradiation. Based on the intrinsic stability of the vitamin B12 framework and recycling of the catalyst, it is evident that this natural catalytic scheme has potential applications in medicinal chemistry and biomaterials. In addition, this strategy, combined with highly specific recognition probes and vitamin B12 circulation-mediated chain-growth polymerization, has a detection limit as low as 910 aM. Furthermore, it is sensitive for sensing in serum samples containing biomarkers and shows great potential for RNA selection and amplification sensing in clinical samples.

Catalytic Reaction with Benzoic Acid Phenylacetylene in the Presence of Complex Catalysts

In this work, we studied the processes of vinyl ester formation by the addition of benzoic acid to phenylacetylene in the presence of complex catalysts of diacetate-di (2-amino-5-methylthio-1,3,4-thiadiazolo) cobalt(II) ([Co(C3H5N3S2)2(CH3COO)2] and tetrakis(2-amino-5-ethylthio-1,3,4-thiadiazole)-zinc(II) dinitrate ([Zn(C4H7S2)4](NO3)2): 1-phenylvinyl benzoate and anti-Markovnikov coupling product - styryl benzoate were obtained. The effect of the nature of solvents on the yields of products in the presence of the [Zn(C4H7S2)4](NO3)2 complex catalyst was studied. The structure of the synthesized vinyl esters was proved by IR, 1H NMR, 13C NMR spectroscopies.

Front Cover: Expanding the Substrate Scope of Acyltransferase LovD9 for the Biosynthesis of Statin Analogues (Chem. Eur. J. 42/2023)

Vinyl and p-nitrophenyl esters have emerged as alternative substrates for the LovD9 acylation mechanism, showing product yields as high as those obtained by α-dimethylbutyryl-S-methyl-3-mercaptopropionate (DMB-SMMP), the thioester for which LovD9 was evolved. More information can be found in the Research Article by G. Jiménez-Osés, F. López-Gallego and co-workers (DOI: 10.1002/chem.202300911).

Expanding the Substrate Scope of Acyltransferase LovD9 for the Biosynthesis of Statin Analogues.

This study identifies new acyl donors for manufacturing statin analogues through the acylation of monacolin J acid by the laboratory evolved acyltransferase LovD9. Vinyl and p-nitrophenyl esters have emerged as alternate substrates for LovD9-catalyzed acylation. While vinyl esters can reach product yields as high as the ones obtained by α-dimethyl butyryl-S-methyl-3-mercaptopropionate (DMB-SMMP), the thioester for which LovD9 was evolved, p-nitrophenyl esters display a reactivity even higher than DMB-SMMP for the first acylation step yet the acylation product yield is lower. The reaction mechanisms were elucidated through quantum mechanics (QM) calculations.

“Greening” Ruthenium–Arene Catalyst Precursors with N-Heterocyclic Carbene Ligands Derived from Caffeine and Theophylline

Two ruthenium–arene complexes with the generic formula [RuCl2(p-cymene)(NHC)] were readily obtained from natural, abundant, and renewable methylxanthine alkaloids used as N-heterocyclic carbene (NHC) precursors. After optimization, the known compound Ru-1 featuring the 1,3,7,9-tetramethylxanthine-8-ylidene ligand was isolated in three steps and 72% overall yield starting from caffeine. Four steps were needed to synthesize complex Ru-2, which sported the bulkier 7-isobutyl-1,3,9-trimethylxanthine-8-ylidene ligand, in 41% overall yield starting from theophylline. Multinuclear NMR analysis confirmed the presence of p-cymene and an NHC ligand within the coordination sphere of both products. Yet, they exhibited a significantly different dynamic behavior in solution at room temperature, due to the larger size of the isobutyl chain compared to a methyl group, which severely restricted the rotation of the arene ligand and caused a loss of symmetry. Complexes Ru-1 and Ru-2 were both highly active catalyst precursors for the transfer hydrogenation of unsaturated substrates with isopropanol under basic conditions (11 examples). They were also efficient promoters for the oxidation of alkenes with sodium periodate. Last but not least, they triggered the synthesis of vinyl esters from 1-hexyne and benzoic acid. For this later reaction, the product distribution varied markedly with the nature of the NHC ligand. Altogether, this study demonstrated that the combination of a labile p-cymene ligand and an ancillary NHC ligand derived from caffeine or theophylline provided an efficient and sustainable access to a wealth of highly active Ru–hydride, −oxo, or −alkyne species that were able to catalyze three miscellaneous organic transformations.

Insights into the FTIR Spectral Fingerprint of Saffron (Crocus sativus L.) Stigmas After Gentle Drying Treatments

Drying of the delicate, red stigmas of the Crocus sativus L. flower is necessary to produce saffron, the most expensive spice in the world. So far, laborious and sample destructive methods were applied to get vital insight into this process following key physicochemical changes. Vibrational spectroscopy tools that allow molecular fingerprinting of plant tissues via multivariate data analysis are still not exploited. This study aimed at gaining new insights into the Fourier-Transform Infrared (FTIR) spectra of saffron on different gentle drying treatments in vacuum or by short-time heating with varying sample loading, energy input, duration etc. Diagnostic spectral bands that were exposed using Principal Component Analysis were assigned to C=O stretching in vinyl or cyclic esters, amides or other inter-molecular interactions of importance for functionality. Above all, the peak at 1160 cm−1 (typical of C-O-C glycosidic bridges) proved a distinguishing feature of short-time heated vs vacuum-dried saffron. Other critical quality attributes of the dried stigmas (physical structure, color, chemical composition), assessed with Scanning Electron Microscopy (SEM), colorimetry, UV-Vis spectrometry and High-Performance Liquid Chromatography (HPLC), indicated both positive and negative effects per drying method. Our work highlights the novelty to combine non-destructive FTIR spectroscopy with conventional techniques for a more insightful evaluation of desired or undesired changes after saffron dehydration. Moreover, the spectral fingerprinting approach offers a cost-effective, eco-friendly solution for rapid, non-invasive control of the raw material that is of high interest for food and nutraceutical applications.

Antioxidant Activities of Dihydromyricetin Derivatives with Different Acyl Donor Chain Lengths Synthetized by Lipozyme TL IM.

Dihydromyricetin (DHM) is a phytochemical with multiple bioactivities. However, its poor liposolubility limits its application in the field. In this study, DHM was acylated with different fatty acid vinyl esters to improve its lipophilicity, and five DHM acylated derivatives with different carbon chain lengths (C2-DHM, C4-DHM, C6-DHM, C8-DHM, and C12-DHM) and different lipophilicity were synthesized. The relationship between the lipophilicity and antioxidant activities of DHM and its derivatives was evaluated with oil and emulsion models using chemical and cellular antioxidant activity (CAA) tests. The capacity of DHM derivatives to scavenge 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS+•) was similar to that of DHM, except for C12-DHM. The antioxidant activity of DHM derivatives was lower than that of DHM in sunflower oil, while C4-DHM exhibited better antioxidant capacity in oil-in-water emulsion. In CAA tests, C8-DHM (median effective dose (EC50) 35.14 μmol/L) exhibited better antioxidant activity than that of DHM (EC50: 226.26 μmol/L). The results showed that in different antioxidant models, DHM derivatives with different lipophilicity had various antioxidant activities, which has guiding significance for the use of DHM and its derivatives.

Synthesis of Vinyl Esters of Fruit Acids under High Pressure

This article describes a method for the synthesis of vinyl esters from fruit acids: malic, tartaric, citric and acetylene, as well as the results of a spectrophotometric analysis of the obtained compounds. Process conditions, product yields, and physicochemical properties of the resulting vinyl esters are given. The homogeneous catalytic reaction of vinylation of malic, tartaric and citric acids with acetylene has been studied and the formation of the corresponding vinyl esters has been proven. The mechanisms of vinylation reactions in the presence of acetylene are proposed. In the synthesis of vinyl ethers, the effect of pressure, temperature, and reaction time on the product yield was established.

An Assessment of Biodiesel Production from Three Species of Micro Algae (Chlamydomonas reinhardtii, Chroococcus species and Ankistrodesmus falcatus)

Aim: Over dependence on fossil fuels has triggered environmental and economic concerns, creating an ultimate need to redirect towards renewable energy options. Hence, the study on biodiesel production from algal biomass.
 Study Design: Modified open pond culture system was applied in the biomass culture and growth was monitored via pH and turbidity.
 Place and Duration of Study: Study was done in the laboratory of the Department of Environmental Management and Toxicology, Federal University of Petroleum Resources, Effurun between June 2020 and July 2021.
 Methodology: Soxhlet extraction was applied in algal oil extraction. Alkali-mediated transesterification of algal oil blends into biodiesel was conducted. Biodiesel blends were characterized physically and spectroscopically for fuel properties and chemical position. The synthesis and fuel properties of biodiesels from three micro algal species: Chroococcus sp, Ankistrodesmus falcatus, and Chlamydomonas reinhardtii were conducted. Due to low algal oil yield, characterization of four types of hybrid oils were prepared: 100 percen(%)t lavender oil (100LO), 10% Ankistrodesmus falcatus oil plus 90% LO (10AN90LO), 10% Chlamydomonas reinhardtii oil plus 90% LO (10CHL90LO), and 10% Chroococcus sp oil plus 90% LO (10CHR90LO).
 Results: The synthesis and fuel properties of biodiesels from the micro algal species: Chroococcus sp, Ankistrodesmus falcatus, and Chlamydomonas reinhardtii gave a percentage yield of algal oil of 29.6%, 23.4% and 15.5%, respectively. The percentage yield of biodiesel from 10AN90LO, 10CHL90LO, 10CHL90LO was 66.7%, 61.7% and 50.0%, respectively. Gas Chromatography-Mass Spectrometry(GC-MS) analysis revealed presence of four fatty acid methyl and vinyl esters namely; hexadecanoic acid methyl ester, octadecadienoic acid methyl ester, methyl stearate, carbonic acid eicosyl vinyl ester and carbonic acid, tetradecyl vinyl ester. Fourier transform infrared spectroscopy(FTIS) confirms that chemicals produced are esters.
 Conclusion: Fuel properties of biodiesel from these selected algal strains appear appreciable when compared to standard limits. Blends with petroleum diesel showed great potential for use in diesel engines.

Poly[bis(serine ethyl ester)phosphazene] regulates the degradation rates of vinyl ester photopolymers

Vinyl esters and carbonates have recently been demonstrated to have considerably lower cytotoxicity than their more commonly used (meth)acrylate counterparts, inspiring their use in the 3D printing of biomaterials. However, the degradation rates of such synthetic photopolymers are slow, especially in the mild conditions present in many biological environments. Some applications, for example, tissue regeneration scaffolds and drug release, require considerably faster biodegradation. Furthermore, it is essential to be able to easily tune the degradation rate to fit the requirements for a range of applications. Herein we present the design and synthesis of hydrolytically degradable polyphosphazenes substituted with a vinyl carbonate functionalized amino acid. Thiolene copolymerization with vinyl esters gave cured polymers which are demonstrated to considerably accelerate the degradation rates of cured vinylester/thiolene polymer scaffolds.Graphical abstract

ATP-Independent and Cell-Free Biosynthesis of β-Hydroxy Acids Using Vinyl Esters as Smart Substrates.

In vitro biosynthetic pathways that condense and reduce molecules through coenzyme A (CoASH) activation demand energy and redox power in the form of ATP and NAD(P)H, respectively. These coenzymes must be orthogonally recycled by ancillary reactions that consume chemicals, electricity, or light, impacting the atom economy and/or the energy consumption of the biosystem. In this work, we have exploited vinyl esters as dual acyl and electron donor substrates to synthesize β-hydroxy acids through a non-decarboxylating Claisen condensation, reduction and hydrolysis stepwise cascade, including a NADH recycling step, catalyzed by a total of 4 enzymes. Herein, the chemical energy to activate the acyl group with CoASH and the redox power for the reduction are embedded into the vinyl esters. Upon optimization, this self-sustaining cascade reached a titer of (S)-3-hydroxy butyrate of 24 mM without requiring ATP and simultaneously recycling CoASH and NADH. This work illustrates the potential of in vitro biocatalysis to transform simple molecules into multi-functional ones.

ATP‐Independent and Cell‐Free Biosynthesis of β‐Hydroxy Acids Using Vinyl Esters as Smart Substrates

AbstractIn vitro biosynthetic pathways that condense and reduce molecules through coenzyme A (CoASH) activation demand energy and redox power in the form of ATP and NAD(P)H, respectively. These coenzymes must be orthogonally recycled by ancillary reactions that consume chemicals, electricity, or light, impacting the atom economy and/or the energy consumption of the biosystem. In this work, we have exploited vinyl esters as dual acyl and electron donor substrates to synthesize β‐hydroxy acids through a non‐decarboxylating Claisen condensation, reduction and hydrolysis stepwise cascade, including a NADH recycling step, catalyzed by a total of 4 enzymes. Herein, the chemical energy to activate the acyl group with CoASH and the redox power for the reduction are embedded into the vinyl esters. Upon optimization, this self‐sustaining cascade reached a titer of (S)‐3‐hydroxy butyrate of 24 mM without requiring ATP and simultaneously recycling CoASH and NADH. This work illustrates the potential of in vitro biocatalysis to transform simple molecules into multi‐functional ones.

Substrate Specificity of the Highly Thermostable Esterase EstDZ3.

Esterases are among the most studied enzymes, and their applications expand into several branches of industrial biotechnology. Yet, despite the fact that information on their substrate specificity is crucial for selecting or designing the best fitted biocatalyst for the desired application, it cannot be predicted from their amino acid sequence. In this work, we studied the substrate scope of the newly discovered hydrolytic extremozyme, EstDZ3, against a library of esters with variable carbon chain lengths in an effort to understand the crucial amino acids for the substrate selectivity of this enzyme. EstDZ3 appears to be active against a wide range of esters with high selectivity towards medium- to long-carbon chain vinyl esters. In-silico studies of its 3D structure revealed that the selectivity might arise from the mainly hydrophobic nature of the active site's environment.

Functional Lignin Building Blocks: Reactive Vinyl Esters with Acrylic Acid.

Introducing vinyl groups onto the backbone of technical lignin provides an opportunity to create highly reactive renewable polymers suitable for radical polymerization. In this work, the chemical modification of softwood kraft lignin was pursued with etherification, followed by direct esterification with acrylic acid (AA). In the first step, phenolic hydroxyl and carboxylic acid groups were derivatized into aliphatic hydroxyl groups using ethylene carbonate and an alkaline catalyst. The lignin was subsequently fractionated using a downward precipitation method to recover lignin of defined molar mass and solubility. After recovery, the resulting material was then esterified with AA, resulting in lignin with vinyl functional groups. The first step resulted in approximately 90% of phenolic hydroxyl groups being converted into aliphatic hydroxyls, while the downward fractionation resulted in three samples of lignin with defined molar masses. For the esterification reaction, the weight ratio of reagents, reaction temperature, and reaction time were evaluated as factors that would influence the modification efficacy. 13C NMR spectroscopy analysis of lignin samples before and after esterification showed that the optimized reaction conditions could reach approximately 40% substitution of aliphatic hydroxyl groups. Both steps only used lignin and the modifying reagent (no solvent), with the possibility of recovery and reuse of the reagent by dilution and distillation. An additional second esterification step of the resulting lignin sample with acetic acid or propionic acid converted 90% of remaining hydroxyl groups into short-chain carbon aliphatic esters, making a hydrophobic material suitable for further copolymerization with synthetic hydrophobic monomers.

Unsaturated polyester fracture toughness mechanism with blending to vinyl ester and MMA

In this research, a method was used to increase the brittleness of unsaturated polyester polymer by mixing it with vinyl ester. The choice of vinyl ester to increase the toughness of this polyester is because it is easy to form and this material has wide applications in engineering. However, this polyester has several weaknesses, namely, it is very stiff, brittle, and unable to withstand cracking loads and breaks easily due to impact. Polyester has a rigid nature because this material has cross-chain links of material that are tightly locked and interconnected with each other. With the addition of this vinyl ester, this tightly connected rigid chain is disrupted by the vinyl ester chain, thereby increasing the toughness of the polyester. Steps were taken to increase the crack resistance of unsaturated polyesters with the addition of vinyl esters, starting with the percentages of 10%, 20%, 30%, and 40% and comparing them with pure polyester. The results obtained showed that the crack resistance of polyester increased with the addition of 40% wt vinyl ester. The results show that the highest fracture toughness value is indicated by the value of the stress intensity factor of K1c=1.752 MPa.m0.5.

Aryloxy Ionic Liquid-Catalyzed Homogenous Esterification of Cellulose with Low-Reactive Acyl Donors.

Ionic liquids (ILs) are recyclable, non-volatile, and can dissolve cellulose, a natural polymer that is insoluble in versatile solvents. Therefore, ILs have been used to modify cellulose. However, 1-ethyl-3-methylimidazolium acetate (EmimOAc), a commercially available IL often used to dissolve and modify cellulose to prepare cellulose-based materials, causes the undesired introduction of an acetyl group derived from the acetate anion of EmimOAc onto the hydroxy group of cellulose during esterification. In this study, for cellulose esterification, we prepared aryloxy ILs as non-carboxylate-type and basic ILs, which can theoretically prevent the undesired introduction of an acyl group from the IL onto the hydroxy group of cellulose. The optimized 1-ethyl-3-methylimidazolium 2-pyridinolate (Emim2OPy) and mixed solvent system achieved rapid cellulose esterification (within 30 min) with an excellent degree of substitution (DS) value (up to >2.9) derived from the employed low-reactive vinyl esters and bio-based unsaturated aldehydes, without any undesired substituent introduction from side reactions.

Facile synthesis of vinyl esters of aromatic carboxylic acids with participation of 2-chloro-4,6-dimethoxy-1,3,5-triazine

In this work, the reaction of derivatives of benzoic acid containing substituents in the aromatic ring (1a-o) with 2-chloro-4,6dimethoxy-1,3,5-triazine (4) in the presence of N-methylmorpholine (6) has been synthesized active triazine esters of carboxylic acids (3a-o). These compounds obtained in the presence of potassium butylate (7) in reaction with vinyl acetate (2) have formed vinyl esters of corresponding aromatic carboxylic acids (5a-o). The electronic effect of the substitutor in the aromatic ring affects on carrying out of the reaction and the nature of obtained products. The structure of the synthesized vinyl esters of aromatic carboxylic acids was confirmed by FT-IR, 1H_NMR, 13C-NMR, and LC/MS spectral analysis, and some of their physical constants were determined.

Dehaloperoxidase Catalyzed Stereoselective Synthesis of Cyclopropanol Esters.

Chiral cyclopropanols are highly desirable building blocks for medicinal chemistry, but the stereoselective synthesis of these molecules remains challenging. Here, a novel strategy is reported for the diastereo- and enantioselective synthesis of cyclopropanol derivatives via the biocatalytic asymmetric cyclopropanation of vinyl esters with ethyl diazoacetate (EDA). A dehaloperoxidase enzyme from Amphitrite ornata was repurposed to catalyze this challenging cyclopropanation reaction, and its activity and stereoselectivity were optimized via protein engineering. Using this system, a broad range of electron-deficient vinyl esters were efficiently converted to the desired cyclopropanation products with up to 99.5:0.5 diastereomeric and enantiomeric ratios. In addition, the engineered dehaloperoxidase-based biocatalyst is able to catalyze a variety of other abiological carbene transfer reactions, including N-H/S-H carbene insertion with EDA as well as cyclopropanation with diazoacetonitrile, thus adding to the multifunctionality of this enzyme and defining it as a valuable new scaffold for the development of novel carbene transferases.

Co-pyrolysis of waste polyester enameled wires and polyvinyl chloride: Evolved products and pyrolysis mechanism analysis

Waste enameled copper wire is an important secondary source of copper and often recovered by removing their organic paint layer through pyrolysis. This research focused on studying co-pyrolysis behaviors of poly(ethylene terephthalate) (PET) paint of waste enameled wires, mixed with a small amount of polyvinyl chloride (PVC) which is part of electric wires or cables. The results indicated that mixing PVC with a mass fraction of 10% into enameled PET wire paint (EPET) would significantly affect pyrolysis products, especially the chlorinated compounds, as well as increase energy consumption of the pyrolysis process. TG-FTIR and Py-GC/MS analyses showed that the chlorinated organics were mainly generated in the second stage of pyrolysis. Chloroesters such as terephthalic acid, di(2-chloroethyl) ester were dominant over other chloroorganic compounds, and their formations were attributed to the addition reaction of aromatic vinyl esters with HCl which formed from PVC pyrolysis. It is also worth mentioning that the chemically active acid chlorides including propanoyl chloride and benzoyl chloride were detected in the products, and they were proposed to be formed from the HCl acidolysis of esters that produced from pyrolytic EPET. Besides pyrolysis products, energy consumption of pyrolysis process also was closely correlated to the interactions between pyrolytic PVC and EPET. The average co-pyrolysis activation energy was calculated by Kissinger-Akahira-Sunose (KAS) method and was about 15 kJ/mol higher than that of EPET. These should be consequences of reactions between HCl and EPET. Since PVC is the minority component in the pyrolysis mixture that HCl eliminated from the few PVC was mostly consumed by EPET to form chloroorganic compounds, which negatively influences EPET degradation.

Identification of the fracture surface of thermoset polyester due to bending load

In this research, an attempt was made to improve the brittle nature of the Unsaturated Polyester (UP) polymer which cannot undergo plastic deformation to be improved to become more resilient by adding Thermoset Vinyl Ester and Methyl Methacrylate (MMA). To show the change in the toughness of the polyester material, a test is carried out to provide a tensile load and a flexural load until the material breaks This work reports the successful fabrication of polyester blends by mixing vinyl esters with different percentages. The test shows that there is a linear relationship between the shape of the fracture surface due to bending loads and observations through SEM which are directly related to the flexural stress properties with the fracture surface morphology. The mixture of polyester with 40% vinyl ester showed the highest flexural stress of 126.88 MPa while for pure polyester of 49.71 MPa this showed an increase of 255.24% compared to pure polyester. This shows that the addition of vinyl ester to polyester resulted in an increase in the toughness of the polyester, but for 100% vinyl ester the return stress decreased by 56.50 MPa. This indicates that due to the breaking of some of the polyester chain networks causes a decrease in the structural stiffness, which results in an increase in the plastic deformation zone fraction.