Carboxylic Esters Research Articles

Sulfide organic polymers as novel and efficient metal-free heterogeneous Lewis acid catalysts for esterification reactions

Organosulfide-based covalent organic polymers (SOPs) were prepared, via click processes, through SN2 or thiol–yne coupling reactions, which exhibited high conversions and efficient recyclability for carboxylic acid esterification reactions.

Correction: WOx/ZrOx functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification

Correction for ‘WOx/ZrOx functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification’ by Vannia C. dos Santos-Durndell et al., Sustainable Energy Fuels, 2023, https://doi.org/10.1039/D2SE01724E.

WOx/ZrOx functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification

Kicking out water: optimising the interaction between support hydrophobicity and surface acid sites in WOx/ZrOx/PMO catalysts unlocks an efficient route for the upgrading of low-quality waste bio-oil feedstocks to biodiesel.

50/50 oil/water emulsion stabilized by pea protein isolate microgel particles/xanthan gum complexes and co-emulsifiers

Properties of 50/50 oil/water emulsion stabilized by pea protein isolate microgel particles (PPIMP)/xanthan gum (XG) and co-emulsifiers were evaluated. Three surfactants with different charging characteristics (lauric arginate, LAE, cationic surfactant; diacetyl tartaric acid esters of mono- and diglycerides, DATEM, nonionic surfactant; sodium stearyl lactate, SSL, anionic surfactant) were selected to co-stable emulsion systems with PPIMP/XG, respectively. The emulsions stabilized by PPIMP/XG with LAE reached the minimal droplet size (21.5 μm). The increased addition of either DATEM or SSL decrease the droplet size of emulsion (except for the 0.8 wt% SSL). The emulsions showed lower apparent viscosity at higher DATEM concentration, whereas the vice-versa was observed in the prepared emulsions with SSL. Surfactants with different charge properties can affect the antioxidant properties of the emulsions. All the emulsions containing LAE, DATEM, or SSL can inhibit oxidation by adjusting the concentration, which could be confirmed in a study on the retention of resveratrol. This study provides a deeper insight into the emulsions co-stabilized by different emulsifiers and can be applied in edible O/W emulsions in the food industry like egg-free mayonnaise. • Pea protein microgels and xanthan gum can obtain stable 50 wt% O/W emulsion. • 0.02 wt% lauric arginate in emulsion reduced droplet size and increased viscosity. • Non-ionic surfactant fell emulsion's viscosity and G′, anionic one did opposite. • The existence of surfactants could enhance the oxidation stability of emulsions.

Lipases as cake batter improvers compared to a traditional emulsifier

Lipases can act on the baking quality of cakes as clean-label improvers. Only little is known about their possible effects on the batter quality of cakes. Especially the importance of the cake formulation has not been studied before. We therefore aim to analyse the effects of seven baking lipases on three different cake formulations (an eggless basic cake, a pound cake and a yeast-based cake) in comparison to the emulsifier DATEM (mono- and diacetyl tartaric acid esters of mono- and diglycerides of fatty acids). The impact on batter density, stickiness and rheological properties was examined. Both the lipase and the cake formulation had an influence on the extent of batter improvement. The greatest lipase-induced effects occurred in the eggless cake, probably because no intrinsic emulsifiers were present. Lipase reactions seemed to be inhibited in the yeast-based cake. For basic cake and pound cake, three lipases decreased batter density (up to 3.7%) and stickiness (up to 42.7%) and caused a liquefaction of the batter. This leads to an eased machinability of lipase-treated batters for cake manufacturing and opens up many possibilities for application of lipases in cakes and other fine bakery goods.

Proteínas vegetais como alternativa ao ovo em biscoitos: uso de farinha de girassol sem óleo e sua proteína isolada como um agente emulsionante

Abstract De-oiled sunflower meal (DSF) and its protein isolate were evaluated as emulsifiers to replace egg yolk powder (EYP) in cookies. The chemical emulsifier DATEM (Diacetyl Tartaric Acid Esters of Mono- and Diglycerides) was used as a positive control. An experimental design of mixtures of the simplex-centroid type was carried out, and the ingredients were expressed as pseudo-components for EYP, DSF, and DATEM emulsifier. The DSF and its sunflower protein isolate (SPI) were tested to validate the design in optimized conditions. Whole meal cookies were analyzed in relation to rheological, physical, technological, and sensory characteristics using the control difference test. In the rheology of the dough, the DSF caused a reduction in the value of hardness, while increasing the parameter of elasticity. Instrumental texture results as well as the specific volume of the samples showed no difference. The control difference test regarding the cookies made with EYP, SPI, and DSF showed that consumers did not give different ratings to cookies made with sunflower as an emulsifier. Therefore, according to the parameters, conditions, and analysis performed, the replacement of EYP by DSF and SPI proved to be satisfactory as an emulsifying agent regarding the preparation of cookies for vegan consumers.

Enantioselective construction of dihydropyranone-fused indoles by [3 + 3] annulation of in situ-derived indolin-3-ones and unsaturated carboxylic esters

This work discloses an N-heterocyclic carbene (NHC) and base-mediated [3 + 3] annulation reaction of unsaturated carboxylic esters and sulfonium salts for rapid and direct access to enantioselective dihydropyrano[3,2-b]indoles.

Photoinduced copper-catalyzed selective three-component 1,2-amino oxygenation of 1,3-dienes.

This study presents a highly effective method for the photoinduced copper-catalyzed 1,2-amino oxygenation of 1,3-dienes. This synthetic strategy involves the dual roles of a single copper catalyst, which can act as a photosensitizer to generate nitrogen radicals and can also react with allyl radicals via single electron transfer (SET) processes. The method produces a range of quaternary carbon-centered allyl carboxylic esters and tertiary ethers with high yields and excellent regioselectivity under mild reaction conditions.

Low-temperature electrolytes based on linear carboxylic ester co-solvents for SiO x /graphite composite anodes.

Silicon-based anode materials have been applied in lithium-ion batteries with high energy density. However, developing electrolytes that can meet the specific requirements of these batteries at low temperatures still remains a challenge. Herein, we report the effect of linear carboxylic ester ethyl propionate (EP), as the co-solvent in a carbonate-based electrolyte, on SiO x /graphite (SiOC) composite anodes. Using electrolytes with EP, the anode provides better electrochemical performance at both low temperatures and ambient temperature, showing a capacity of 680.31 mA h g-1 at -50 °C and 0.1C (63.66% retention relative to that at 25 °C), and a capacity retention of 97.02% after 100 cycles at 25 °C and 0.5C. Within the EP-containing electrolyte, SiOC‖LiCoO2 full cells also exhibit superior cycling stability at -20 °C for 200 cycles. These substantial improvements of the EP co-solvent at low temperatures are probably due to its involvement to form a solid electrolyte interphase with high integrity and facile transport kinetics in electrochemical processes.

Selective reduction of carboxylic esters enabled by a coaxial double-tube continuous-flow reactor with on-the-fly H2 degassing

Herein, a coaxial double-tube continuous-flow reactor is developed, which allows on-the-fly removal of the generated hydrogen gas from the reaction solution. This enables selective borohydride reduction of carboxylic esters to primary alcohols.

ISOLATION AND CHARACTERIZATION OF BIOACTIVE CONSTITUENT OF N-BUTANOL SEED EXTRACT OF Azadirachta indica

Extraction of the seed powdered material of Azadirachta indica followed by an extensive column chromatography of the n-butanol portion on silica gel, purification over sephadex LH20 and subsequently HPTLC resulted in to the isolation of a pale yellowish solid coded as compound MND. The isolated bioactive constituent was found to have mp of 222-224oC. The structure was elucidated using a combination of 500 MHZ and 125MHZ 1-D and 2-D NMR techniques (COSY, NOESY, HSQC, DEPT and HMBC). Thus, the isolate (MND) was determined as 4a, 7 – dihydroxy – 7 – methyl – 1 – (3, 4, 5 – trihydroxy – 6– hydro methyl – tetrahydropyran – 2 – yloxy) – 1 -, 4a, 5, 6, 7, 7a, hexahydro – cyclopenta [C] pyran – 4 – carboxylic acid methyl ester (Ipolamiide). The Antimicrobial properties of the compound MND and partition portion of the extracts were tested against S. aureus, S. pyogenes, P. vulgari, P.aeruginosa, K. pneumoniae, E. coli, S. typhi, P. digitatum, C. albicans and P. nototum. The antimicrobial sensitivity test indicated that various partition portion of the extracts inhibited the growth of S. aureus , S. pyogenes P. aeruginosa, E. coli, S. typhi, K. pneumoniaer, P. digitatum, C. albicans and P. nototum with 42mm, 38mm, 31mm, 29mm, 22mm, 30mm, 26mm, 27mm , 21mm and 20 mm while the highest activity of the isolate (MND) was exhibited against S. aureus, P. aeruginosa, E. coli and S. typhi with 42 mm, 38 mm, 31mm and 39mm respectively.

Determination of E 472b emulsifiers in foamed food formulations by high-performance thin-layer chromatography‒fluorescence detection

E 472b emulsifiers, defined as lactic acid esters of mono- and diacylglycerides, are food emulsifiers widely used in foamed food formulations. So far, only qualitative methods for analyzing E 472b emulsifiers have been published. Thus, a new method was developed for determining E 472b in different foamed food formulations by high-performance thin-layer chromatography with fluorescence detection (HPTLC‒FLD). The proposed method allows simple and fast E 472b emulsifier extraction from the food matrix and points out an analytical approach for quantifying these emulsifiers using a commercial E 472b emulsifier as the reference standard. Limits of decision with 56‒59 ng of E 472b emulsifier/zone and limits of quantification with 172‒179 ng of E 472b emulsifier/zone in three foamed model food formulations, respectively, as well as satisfactory repeatability (n = 6) and reproducibility (n = 6) exposed by low relative standard deviation < 8% proved the method suitable for the sensitive and reliable determination of E 472b emulsifiers. Recoveries between 96 and 109.3% were obtained for all investigated model systems. In commercial foamed food formulations from the German market, the E 472b emulsifier content ranged between 0.1 and 0.6 g/100 g.

Minimalistic Artificial Catalysts with Esterase-Like Activity from Multivalent Nanofibers Formed by the Self-Assembly of Dipeptides.

Imitating and incorporating the multiple key structural features observed in natural enzymes into a minimalistic molecule to develop an artificial catalyst with outstanding catalytic efficiency is an attractive topic for chemists. Herein, we designed and synthesized one class of minimalistic dipeptide molecules containing a terminal -SH group and a terminal His-Phe dipeptide head linked by a hydrophobic alkyl chain with different lengths, marked as HS-C n+1-His-Phe (n = 4, 7, 11, 15, and 17; n + 1 represents the carbon atom number of the alkyl chain). The His (-imidazole), Phe (-CO2 -) moieties, the terminal -SH group, and a long hydrophobic alkyl chain were found to have important contributions to achieve high binding ability leading to outstanding absolute catalytic efficiency (k cat/K M) toward the hydrolysis reactions of carboxylic ester substrates.

Queijo Serra da Estrela PDO Cheese: Investigation into Its Morpho-Textural Traits, Microbiota, and Volatilome.

Queijo Serra da Estrela is a PDO Portuguese cheese produced through coagulation of raw ewe’s milk using cardoon (Cynara cardunculus L.) flowers. The present research was aimed at depicting an up-to-date and comprehensive overview of the microbiota of Queijo Serra da Estrela cheese. To this end, viable counting and metataxonomic analysis were carried out on cheeses sampled from four Portuguese artisan producers. Physico-chemical and morpho-textural analyses were also performed, together with the analysis of volatile organic compounds (VOCs). Finally, non-starter lactic acid bacteria (NSLAB) isolated from the cheeses were characterized for their enzymatic activities using a semi-quantitative method. According to the metataxonomic analysis, Lactococcus lactis and Lactococcus piscium were the species occurring at the highest relative abundance. The isolates collected from the cheeses were assigned to Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus lactis, Levilactobacillus brevis, Latilactobacillus graminis, Leuconostoc mesenteroides, and the Lacticaseibacillus casei group. The enzymatic characterization of these cultures highlighted esterase, aminopeptidase, acid phosphatase, beta-galactosidase, alpha-glucosidase, and beta-glucosidase among the major enzymatic activities. Fungal populations were dominated by Debaryomyces hansenii and Kurtzmaniella zeylanoides; however, species rarely found in cheese (e.g., Candida boidinii, Vishniacozyma victoriae, and Starmerella) were also detected. The volatile compounds characterizing the analyzed cheeses were carboxylic acids and esters, followed by carbonyl compounds and alcohols.

Merging Photocatalytic C–O Cross-Coupling for α-Oxycarbonyl-β-ketones: Esterification of Carboxylic Acids via a Decarboxylative Pathway

Herein, the first merged photocatalytic pathway for the C-O cross-coupled esterification of carboxylic acids to α-oxycarbonyl-β-ketones has been demonstrated. Decarboxylation of α,β-unsaturated acids promotes the formation of the β-ketone fragment of the desired product. Water as the source of oxygen for the ketone segment and aerial oxygen as an oxidant make the present synthetic methodology green and sustainable. This new C═O and C-O bond-forming methodology takes place in a cascade manner under a dual Ir/Pd-catalytic pathway, with the liberation of H2O and CO2 as the only byproducts.

Boron Catalysis in the Transformation of Carboxylic Acids and Carboxylic Acid Derivatives

AbstractCarboxylic acids, amides, and esters are ubiquitous motifs in functional organic molecules. However, the reactivities of these high oxidation state carbonyl compounds are far lower than ketones and aldehydes, and catalysts applicable to transform this class of carbonyl compounds are limited. On the other hand, boron catalysts have found various applications in the transformation of carbonyl compounds by taking advantage of the unique properties derived from their vacantp‐orbitals. The continuous advancement of boron catalysis has realized several unprecedented direct transformations of carboxylic acids, amides, and esters in the past decade. In this review, representative achievements of boron catalysis are summarized according to reaction types by focusing on their applications to non‐activated carboxylic acids, amides, and esters.

Identification and Quantification of Organic Contaminants and Evaluation of Their Effects on Amine Foaming in the Natural Gas Sweetening Industry.

Contamination is a leading cause of corrosion, foaming, and amine-absorption capacity limitation, predominantly foaming. There is currently an urgent need to identify the sources of amine foaming and eliminate them or reduce their impacts. Gas chromatography-mass spectrometry (GC-MS) and a sample pretreatment method were developed to identify and quantify the organic contaminants. Linear hydrocarbons (C12-C22), long-chain carboxylic acids and esters, alcohol ethoxylates, and benzene derivatives were detected, characterized, and quantified in amine solutions. Furthermore, the effects of the contaminant concentrations on foaming behavior were also investigated by adding those contaminants. The results reveal that the main issue of foaming is due to the presence of unsaturated fatty acids and alcohol ethoxylates, even with a small amount of 10 ppm, whereas benzene derivatives like methylpyridine, quinoline, methyl naphthalene, benzyl alcohol, octahydroacridine, and linear hydrocarbons have little effect on amine foaming, even with an amount up to 2000 ppm. Therefore, it is necessary to monitor the existence and content of these surface-active contaminants.

Divalent 2-(4-Hydroxyphenyl)benzothiazole Bifunctional Chelators for 64Cu Positron Emission Tomography Imaging in Alzheimer's Disease.

Herein, we report a new series of divalent 2-(4-hydroxyphenyl)benzothiazole bifunctional chelators (BFCs) with high affinity for amyloid β aggregates and favorable lipophilicity for blood-brain barrier penetration. The addition of an alkyl carboxylate ester pendant arm offers high binding affinity toward Cu(II). The novel BFCs form stable 64Cu-radiolabeled complexes and exhibit promising partition coefficient (logD) values of 1.05-1.85. Among the five compounds tested, the 64Cu-YW-15 complex exhibits significant staining of amyloid β plaques in ex vivo autoradiography studies. In addition, biodistribution studies show that 64Cu-YW-15-Me exhibits moderate brain uptake (0.69 ± 0.08 %ID/g) in wild type mice.

Enzymatic Strategies for the Preparation of Pharmaceutically Important Amino Acids through Hydrolysis of Amino Carboxylic Esters and Lactams.

The most relevant lipase-catalyzed strategies for the synthesis of pharmaceutically important cyclic and acyclic α-, β- and γ-amino carboxylic acid enantiomers through hydrolysis of the corresponding amino carboxylic esters and lactams, over the last decade are overviewed. A brief Introduction part deals with the importance and synthesis of enantiomeric amino acids, and formulates the objectives of the actual work. The strategies are presented in the Main Text, in chronological order, classified as kinetic, dynamic kinetic and sequential kinetic resolution. Mechanistic information of the enzymatic transformations is also available at the end of this overview. The pharmacological importance of the enantiomeric amino acids is given next to their synthesis, in the Main Text, and it is also illustrated in the Conclusions and Outlook sections.

Diels-Alder Reactivity of Allenylboronic Acid Pinacol Ester and Related Dienophiles: Mechanistic Studies and Distortion/Interaction-Activation Strain Model Analysis.

A DFT study of the Diels-Alder reactions of vinylboronic acid pinacol ester, allenylboronic acid pinacol ester, methyl acrylate, and methyl 2,3-butadienoate with cyclopentadiene has been performed. Competitive mechanisms for the reactions of the carboxylic esters have been fully investigated, and similar results to those previously found for the organoboron compounds were obtained. Moreover, reactivity and selectivity patterns were correctly reproduced. The distortion/interaction-activation strain energy model analysis provided a rationale to explain the experimental outcome of the studied [4 + 2] cycloadditions. While the regioselectivity of the allenyl compounds and the relative reactivity of the boronic and carboxylic esters appear to originate from electronic effects that arise from orbital overlap and correlate with the energies of the vacant orbitals of the dienophiles, the lower reactivity of the allenes relative to the vinyl compounds may be due to the distortion of the dienophiles.