Acid Esters Research Articles

Amino-acid-functionalized methanesulfonate ionic liquids as effective and reusable catalysts for oleic acid esterification

Five new amino-acid-functionalized methanesulfonate ionic liquids ([AAH][CH3SO3]-ILs) were prepared using methanesulfonic acid and amino acids (AAs). The catalytic performances of the five synthesized [AAH][CH3SO3]-ILs were evaluated for biodiesel synthesis via the esterification of oleic acid with methanol. Among them, IL [GluH][CH3SO3] exhibited the optimal catalytic activity in the oleic acid esterification. An experimental design based on the RSM-BBD was used to optimize the reaction conditions. A conversion rate of 96.8 % was attained using the [GluH][CH3SO3] catalyst for the oleic acid esterification at a catalyst load of 12 wt%, a molar ratio of 19.6:1, a reaction time of 3.5 h and a temperature of 103 °C. The [GluH][CH3SO3]-catalyzed oleic acid esterification followed first-order kinetics with the activation energy and frequency factor of 9.86 kJ·moL−1 and 0.47 min−1, respectively. The catalytic activity of the [GluH][CH3SO3] catalyst did not considerably change during ten consecutive cycles of the esterification reaction. Operational simplicity, high conversion rate along with good reusability makes the IL [GluH][CH3SO3] a promising catalyst for replacing traditional catalysts for the biodiesel preparation via the fatty acids esterification.

Accumulation of Acyl Plastoquinol and Triacylglycerol in Six Cyanobacterial Species with Different Sets of Genes Encoding Type-2 Diacylglycerol Acyltransferase-like Proteins.

Recently, acyl plastoquinol (APQ) and plastoquinone-B (PQ-B), which are fatty acid esters of plastoquinol and plastoquinone-C respectively, have been identified as the major neutral lipids in cyanobacteria. In Synechocystis sp. PCC 6803, Slr2103 having homology with the eukaryotic enzyme for triacylglycerol (TAG) synthesis, diacylglycerol acyltransferase 2 (DGAT2), was identified as responsible for the synthesis of these plastoquinone-related lipids. On the other hand, TAG synthesis in cyanobacteria remains controversial due to the low accumulation level within cyanobacterial cells together with the high contamination level from the environment. In this study, to quantify more precisely and elucidate the relationship between the accumulation of neutral lipids and the presence or absence of DGAT2-like genes, plastoquinone-related lipids and TAG were analyzed directly from total lipids of six cyanobacterial species with different sets of genes encoding DGAT2-like proteins belonging to two distinct subclades. The results showed that the synthesis of these neutral lipids is highly dependent on clade A DGAT2-like proteins under the culture conditions used in this study, although accumulation level of TAG was quite low. In contrast to APQ highly abundant in saturated fatty acids, the fatty acid composition of TAG was species-specific and partly reflected the total lipid composition. Gloeobacter violaceus PCC 7421, which lacks a DGAT2-like gene, accumulated APQ with a high proportion of C18:0, suggesting APQ synthesis by an unidentified acyltransferase.

Microwave-assisted esterification of oleic acid using pyrrolidonium-based bronsted-acidic ionic liquids catalyst

Biodiesel is a liquid fuel obtained by the transesterification reaction of triglycerides and the esterification reaction of free fatty acids. In this study, pyrrolidonium-based Brønsted-acidic ionic liquids (ILs) were applied as catalysts for the production of biodiesel by microwave-assisted esterification of oleic acid with methanol. The effects of reaction temperature, catalyst amount, methanol/oleic acid molar ratio, and reaction time on the oleic acid conversion were investigated. Under optimal conditions, the results demonstrated that N-methyl-2-pyrrolidonium hydrogen sulfate (IL1) and 2-pyrrolidonium hydrogen sulfate (IL2) can achieve conversion rates exceeding 98 %. A comparative analysis with other IL catalysts showed the superior performance of pyrrolidonium-based ILs, especially in terms of Turn Over Frequency (TOF) values. To investigate the effects of different heating methods on the esterification of oleic acid, the esterification reaction was carried out using both conventional and microwave methods. The microwave method is more effective than the conventional method. The reusability of the IL catalyst was investigated, and the recovered catalyst showed excellent stability when it was reused for five consecutive runs without significant loss of activity.

Effect of Density of Acrylic Acid Ester on Sulfonate-Modified Polycarboxylate Superplasticizers on Cementitious Systems

To tackle high viscosity in fresh concretes, especially high-performance concrete, the research of polycarboxylate superplasticizers (PCEs) is relevant. By designing the molecular structure of PCEs, problems such as pumping difficulties in high viscosity of high-performance concrete can be solved. Therefore, in this paper, a suite of novel viscosity reducing PCEs containing sulfonic acid groups and different acrylate densities were synthesized on the basis of inventive molecular structure design, and characterized to determine the predicted structure. The maximum adsorption, the best fluidity, and the Minimum zeta potential value can be seen for PCEs with a small number of ester groups (PCE-MA0.5) due to the combination of the rigidity of its backbone and the density of the adsorption groups. Moreover, the investigation of working mechanism showed the introduction of ester groups can significantly reduce viscosity, but also reduces the adsorption capacity. This research aims to propose a feasible method for synthesizing PCE with superior processability and viscosity reduction capability in cement and concrete.

Fecal fatty acid-linked bile acid profiles in pediatric patients with ulcerative colitis

ObjectiveEffect of gut dysbiosis on fatty acid (FA) linked 3β-hydroxy-bile acid esters (FA-isoBAs) formation is currently unknown. This study aimed to investigate the profile of FA-isoBAs in fecal samples from pediatric patients with ulcerative colitis (UC). MethodsFecal samples were collected from seven pediatric patients diagnosed with UC and seven age-matched healthy controls. Liquid chromatography-tandem mass spectrometry (LC/MS) method was set up for quantifications of thirteen different FA-isoBAs, including three new FA-isoBAs which had never been characterized. Method validation tests were performed with optimization of sample preparation. Statistical analyses were conducted to compare FA-isoBA concentrations between UC patients and healthy controls. ResultsThe LC/MS method had sufficient linearity (r > 0.998), with the low detection limit (0.03–2.82 nmol/g stool), and limits of quantification (0.10–9.40 nmol/g stool) for all FA-isoBAs. The total FA-isoBAs concentration in UC patients was significantly lower than healthy controls, regardless of the degree of the disease severity. The UC subjects had markedly increased primary bile acid (BA) levels with decreased secondary BAs. Propionic acid-linked isoBA and stearic acid-linked 12-oxo-isolithocholic acid were newly identified from healthy subjects but they were not present in UC subjects. In agreement with the previous report, composition of long-chain (C16-C18) FA-linked BAs dominated over short-chain FA-linked BAs both in healthy and disease subjects. ConclusionThe present study reported the fecal FA-isoBA profiles in pediatric UC patients for the first time. The results open the door to the new field that investigates the role of these microbial-driven BAs in gastrointestinal health.

A 11B-NMR Method for the In Situ Monitoring of the Formation of Dynamic Covalent Boronate Esters in Dendrimers

The in situ monitoring of dynamic covalent macromolecular boronate esters represents a difficult task. In this report, we present an in situ method using fluoride coordination and 11B NMR spectroscopy to determine the amount of boronate esters in a mixture of boronic acids and cis-diols. With fluoride coordination, the boronic acid and boronate esters afforded trifluoroborate and fluoroboronate esters, giving identical resonances at 3 and 9 ppm in the 11B NMR spectra. The same titration did not alter the resonance of amine-coordinated boronate esters, which gave resonances of 14 ppm in the 11B NMR spectra. Therefore, boronic acids, boronate esters, and amine-coordinated boronate esters gave three identical resonances, and the ratio of each component was obtained by deconvolution for a further equilibrium analysis. This method monitored the conversion among three species in various conditions, including separation. Accordingly, boronate esters were more stable after precipitation than chromatography, in which 29% and 20% of boronate esters were lost after purification. This method was applied to study the reaction between the boronic acid-decorated defect lysine dendron (16) and dopamine. No boronic acid signal was observed after adding 1 equivalent of dopamine; no boronic acid signal was observed in the NMR spectrum. According to the spectrum, the product contains 65% boronate ester and 35% N–B-coordinated derivatives. This method helps identify the presence of the three intermediates and provides more insights into this reaction.

Synthesis and structural characterization BODIPY-based compounds for fluorescence sensing of β-amyloid aggregates

Alzheimer's disease (AD) is a neurodegenerative disorder associated with aging. According to the amyloid cascade hypothesis, the aggregation and accumulation of β-amyloid (Aβ) peptides in the brain as Aβ plaques is a critical process in the pathogenesis of AD. Among the existing diagnosis methods, fluorescence detection of β-amyloid (Aβ) has emerged as an alternative method due to its advantages such as real-time detection, low cost, not exposed to radiation, and high resolution for early diagnosis of Alzheimer's disease (AD). In this study, we designed and synthesized BODIPY-based compounds (BODIPY-3, BODIPY-4 and BODIPY-5) for the fluorescence detection of Aβ aggregates. In the fluorescence studies for detecting Aβ, BODIPY-5 with the squaric acid ester unit at the meso position of the BODIPY core showed a promising effect with an 11.7 μM Kd value.

Modeling high-pressure viscosities of fatty acid esters and biodiesel fuels based on modified rough hard-sphere-chain model and deep learning method

Modeling high-pressure viscosities of fatty acid esters and biodiesel fuels based on modified rough hard-sphere-chain model and deep learning method

A Green Chemistry Approach to Catalytic Synthesis of Ethyl Levulinate

Esterification of levulinic acid with ethanol was investigated using deep eutectic systems based on choline chloride and oxalic or p-toluenesulfonic acid as catalysts under conventional heating and alternative energy inputs, namely microwave, ultrasound, and mechanochemical treatment. The experiments were performed under varying operating conditions such as catalyst type and loading, alcohol to carboxylic acid molar ratio, temperature, or time. The obtained results demonstrate the overall better catalytic performance of the p-toluenesulfonic acid-based deep eutectic mixture in comparison with the oxalic acid-based analogue. The best results: levulinic acid conversion of 76% and 58%, for p-toluenesulfonic and oxalic acid containing deep eutectic systems, respectively, with 100% selectivity for both cases, were achieved for microwave-assisted synthesis with 5 wt.% of catalyst and excess alcohol to acid (molar ratio 5), at 413.15 K and for 10 min. The main advantage of all of the alternative activation methods studied (microwaves, ultrasounds, and ball mill processing) was the significant reduction in the reaction time.

Discovery of two new long chain fatty acid esters of flavonol glycoside from Pollen Typhae Carbonisatus and their protective effects on HBMECs

ABATRACT Two new compounds, namely, isorhamnenin-3-O-neohesperidin-6′′-linoleic acid ester (1) and isorhamnenin-3-O-neohesperidin-6′′-palmitate (2), along with 17 known compounds, were isolated from Pollen Typhae Carbonisatus (PTC). Their structures were elucidated on the basis of one-dimensional (1D)-, two-dimensional (2D)-nuclear magnetic resonance (NMR), and high-resolution electrospray ionization mass spectrometry (HRESIMS) spectroscopic data analyses. The two new compounds (1 and 2) exhibited a protective effect in a dose-dependent manner and promoted tube generation in the oxygen-glucose deprivation/reoxygenation (OGD/R)-induced human brain microvascular endothelial cells (HBMECs).

Metal-Exchanged Phosphomolybdic Acid Salts-Catalyzed Esterification of Levulinic Acid

We examined the effectiveness of metal-exchanged phosphomolybdic acid salts in converting levulinic acid, derived from biomass, into valuable products (alkyl levulinate). We prepared salts of phosphomolybdic acid using different metals (Fe3+, Al3+, Zn2+, Cu2+, Mn2+, Ni2+, and Co2+). The influence of metal cations on the conversion and selectivity of the reactions was assessed. We found that the salts prepared with iron and aluminum phosphomolybdate were the most effective catalysts for the esterification of levulinic acid with methanol, with the conversion and selectivity tending towards 100% after 6 h of reaction at a temperature of 323 K. The effect of catalyst loading and its recovery and reuse was evaluated; the results from the reaction using aluminum phosphomolybdate remained similar for four cycles of use. The influence of temperature on conversion and selectivity was investigated between 298 and 353 K. The reactivity of different alcohols with a carbon chain size of C1-C4 was assessed and conversions above 65% were obtained for all alcohols tested under the conditions evaluated, except for tert-butyl alcohol. These catalysts are a promising alternative to the traditional soluble and corrosive Brønsted acid catalysts. The superior performance of these catalysts was ascribed to the higher pH decline triggered by the hydrolysis of these metal cations.

Maternal Thyroid Hormones as Mediators between Phthalate Exposure and Neonatal Birth Weight: A Cross-Sectional Study from the Zunyi Birth Cohort.

Studies have shown that exposure to phthalates can affect neonatal birth weight. However, epidemiological evidence on the mediating role of maternal thyroid hormones is limited. Therefore, this study, based on the Compliance Birth Cohort, aimed to reveal the potential mediating function of maternal thyroid hormones during pregnancy between phthalic acid ester (PAE) exposure and neonatal birth weight. The study included 1274 mother-infant pairs. Linear regression analysis revealed a negative association between MIBP and neonatal birth weight (β = -62.236; 95% CI: -118.842, -5.631). Bayesian kernel-machine regression (BKMR) indicated a nonlinear negative association between PAE metabolites (PAEs) and birth weight. Linear regression analysis revealed a positive association between neonatal birth weight and FT3 (β = 41.605; 95% CI: 2.631, 80.380). The BKMR model also found a positive association between thyroid hormones and birth weight but in a nonlinear manner. Additionally, linear regression analyses showed that TSH, TT3, TT4, FT3, and FT4 were associated with PAEs. The BKMR model revealed an inverted U-shaped association of PAEs with TT3 and FT3 and a nonlinear association with TSH, TT4, and FT4. Structural equation modeling revealed that MMP, MIBP, MBP, MEHP, MOP, MBZP, and MEOHP contributed to a net reduction in neonatal birth weight of 32 g through the TT3, FT3, TT4, and FT4 pathways. The findings suggest that exposure to PAEs during pregnancy leads to a reduction in neonatal birth weight, possibly due to the involvement of maternal thyroid hormones as mediators. Controlling maternal thyroid hormone levels during pregnancy may be a viable method to reduce the harmful effects of phthalate exposure on the developing fetus.

Synthesis of fluorinated acid-functionalized, electron-rich nickel porphyrins.

In this study, novel fluorinated carboxylic acid esters of the generic structure TfO-CH2-(CF2) n -COOCH3 (n = 2,4,6, Tf = triflate) were synthesized. The triflates were reacted with 2-hydroxy-3,4,5-trimethoxybenzaldehyde via Williamson ether syntheses. The resulting electron-rich compounds were used as aldehydes in the Rothemund reaction with pyrrole to form ester-substituted porphyrins. After metalation with Ni(acac)2 and hydrolysis electron-rich porphyrins were obtained, that are equipped with covalently attached long chain acid substituents. The target compounds have potential applications in catalysis, sensing, and materials science. The fluorinated aliphatic carboxylic acids (TfO-CH2-(CF2) n -COOCH3) with triflate as leaving group in terminal position are easily accessible and versatile building blocks for attaching long chain acids (pK a 0-1) to substrates in Williamson ether-type reactions.

One-Step Esterification of Phosphoric, Phosphonic and Phosphinic Acids with Organosilicates: Phosphorus Chemical Recycling of Sewage Waste.

Global concerns regarding the depletion and strategic importance of phosphorus resources have increased demand for the recovery and recycling. However, waste-derived phosphorus compounds, primarily as chemically inert phosphoric acid or its salts, present a challenge to their direct conversion into high-value chemicals. We aimed to develop an innovative technology that utilizes the large quantities of sewage waste, bypasses the use of white phosphorus, and enables esterification of phosphoric acid to produce widely applicable phosphate triesters. Tetraalkyl orthosilicates emerged as highly effective reagents for the direct triple esterification of 85% phosphoric acid, as well as the esterification of organophosphinic and phosphonic acids. Furthermore, we achieved esterification of recovered phosphoric acid with tetraalkyl orthosilicate, thus pioneering a recycling pathway from sewage waste to valuable phosphorus chemicals. Experimental and theoretical investigations revealed a novel mechanism, wherein tetraalkyl orthosilicates facilitate multimolecular aggregation to achieve alkyl transfer from tetraalkylorthosilicate to phosphoric acid via multiple proton shuttling.

Fermentation and Microencapsulation of Red Palm Oil as a Nutraceutical Source

Red palm oil (RPO) has various bioactive and nutritional components with high potential to be developed as a source of nutraceuticals in addition to its potential as a functional food. The fermentation technology is a processing process that affects metabolite activity, increasing the durability of a product. Staphylococcus epidermidis is one of the bacteria that is generally used in the sugar and oil fermentation process. RPO fermentation by Staphylococcus epidermidis is supposed to increase nutraceutical value by adding probiotic properties to RPO products. Moreover, the instability of bioactive compounds in RPO needs to be protected with coating technology microencapsulation. So, this study aims to formulate a microencapsulation procedure for fermented RPO using Staphylococcus epidermidis ATCC 12228 as a potential nutraceutical. RPO was fermented using S. epidermidis with three variations of MRS media and RPO comparison, then microencapsulated using emulsification and extrusion methods. The physicochemical properties and bioactivity of the product, microcapsule, were then analyzed. Our data shows that RPO fermentation was able to increase the chemical components. RPO fermentation produced more 1,2-Benzenedicarboxylic acid (2-Ethylhexyl) ester. Furthermore, microencapsulation of fermented RPO has better yield, efficiency, and solubility in water than non-fermented RPO microencapsulation. Moreover, our work also shows that the microencapsulation process increased RPO stability.

Photochemical Deracemization of N‐Carboxyanhydrides En Route to Chiral α‐Amino Acid Derivatives

AbstractReadily accessible, racemic N‐carboxyanhydrides (NCAs) of α‐amino acids underwent a deracemization reaction upon irradiation at λ=366 nm in the presence of a chiral benzophenone catalyst. The enantioenriched NCAs (up to 98 % ee) serve as activated α‐amino acid surrogates and, due to their instability, they were directly converted into consecutive products. N‐Protected α‐amino acid esters were obtained after reaction with MeOH and N‐benzoylation (14 examples, 70 %‐quant., 82–96 % ee). Other consecutive reactions included amide (ten examples, 65 %‐quant., 90–98 % ee) and peptide (three examples, 75–89 %, d. r.=97/3 to 94/6) bond formation. Limitations of the method relate for some NCAs to issues with solubility, photooxidation, and high configurational lability.

Asymmetric Synthesis of 3,3′-Pyrrolidonyl Spirooxindole-5′-Carboxylic Ester from l-Tryptophan

AbstractA highly efficient, multi-gram scale asymmetric synthesis of 3,3′-pyrrolidonyl spirooxindole-5′-carboxylic ester, which could be a potential precursor for the synthesis of cyanogramide, is accomplished from commercially available l-1-methyltryptophan in two pots. Fluoride-promoted desilylative spiro-cyclization of (semi) in situ generated isocyanate derived from l-1-methyltryptophan is the key reaction. Further, a variety of arene-substituted 3,3′-pyrrolidonyl spirooxindole-5′-carboxylxic acid esters were synthesized by late stage functionalization of easily accessible 3,3′-pyrrolidonyl spirooxindole-5′-carboxylic ester.

Photochemical Deracemization of N-Carboxyanhydrides En Route to Chiral α-Amino Acid Derivatives.

Readily accessible, racemic N-carboxyanhydrides (NCAs) of α-amino acids underwent a deracemization reaction upon irradiation at λ=366 nm in the presence of a chiral benzophenone catalyst. The enantioenriched NCAs (up to 98 % ee) serve as activated α-amino acid surrogates and, due to their instability, they were directly converted into consecutive products. N-Protected α-amino acid esters were obtained after reaction with MeOH and N-benzoylation (14 examples, 70 %-quant., 82-96 % ee). Other consecutive reactions included amide (ten examples, 65 %-quant., 90-98 % ee) and peptide (three examples, 75-89 %, d. r.=97/3 to 94/6) bond formation. Limitations of the method relate for some NCAs to issues with solubility, photooxidation, and high configurational lability.

Asymmetric Organocatalysed Synthesis of (R)-Mandelic Acid Esters and α-Alkoxy Derivatives from Commercial Sources.

Optically active mandelic acid esters represent a highly valuable class of building blocks in organic synthesis and recurrent motifs embedded in bioactive compounds and drugs. Herein, we provide an enantioselective one-pot synthesis based on Knoevenagel condensation/asymmetric epoxidation/domino ring-opening hydrolysis (DROH) sequence to the crude mandelic acids, which underwent a final esterification step to (R)-methyl mandelates. These products have been obtained in good to high overall yield and enantioselectivity, using commercially and widely available reagents and catalyst including aldehydes, phenylsulfonyl acetonitrile, cumyl hydroperoxide, water and an epi-quinine-derived urea as the organocatalyst. Moreover, the versatility of the process has been demonstrated to prepare the corresponding α-alkoxy esters in highly enantioselective manner, when using primary alcohols in a domino ring-opening esterification (DROE) step. This system is a first example of non-enzymatic catalytic one-pot protocol which allows a straightforward asymmetric synthesis of highly valuable mandelic acid derivatives from aldehyde feedstocks.

Chemical and Sensory Profile of Grape Distillates Aged in Quercus alba Casks Previously Used for Sherry Wine or Brandy.

This work investigates the influence of oak-cask ageing on the chemical composition and sensory profile of a variety of grape distillates. Wine spirit, wine distillate, neutral alcohol, and grape marc distillate were investigated. It is known that the characteristics of the ageing casks may have a considerable impact on the ageing process, so casks that had previously contained some type of sherry wine, sherry cask®, and casks that had previously contained brandy were studied. The results showed that ageing in either type of cask resulted in significant changes regarding volatile compound composition and a noticeable increase in phenolic and furfural compound content. Furthermore, sherry casks® contributed with sherry wine characteristic compounds that enriched the aromatic profile of the distillates, such as a greater increase in ethyl esters of organic acids. A less noticeable evolution was exhibited by the distillates with higher levels of congeners (wine spirit and grape marc distillate) when compared to wine distillate or neutral alcohol, where changes due to ageing were more evident. The sensory analysis confirmed that ageing significantly modified the organoleptic characteristics of all the distillates, with an increasing perception of certain notes such as oak, vanilla, spicy, and vinous when aged in sherry cask®.