Synthesis Of Esters Research Articles

Catalytic Fatty Acid Methyl Esters (FAMEs) Synthesis Using Lepidium aucheri Seed Oil and Its Antibacterial Potential

Catalytic Fatty Acid Methyl Esters (FAMEs) Synthesis Using Lepidium aucheri Seed Oil and Its Antibacterial Potential

Copper‐Catalyzed Simultaneous Dehydrogenation and Enantioselective Allylic Oxidation of Alkanes Using Chiral Heterogeneous Ligands to Produce Allylic Esters and Theoretical Investigation of the Mechanism

ABSTRACTA new asymmetric method for preparing chiral allylic esters from various unactivated alkanes through simultaneous dehydrogenation and enantioselective allylic oxidation in the presence of chiral heterogeneous oxazoline–based ligands is reported for the first time. For this purpose, chiral amino oxazoline ligands, synthesized from chiral amino alcohols and cyanogen bromide, were immobilized on modified MCM‐41 mesoporous silica. These chiral heterogeneous ligands were then characterized using Fourier‐transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and Brunauer–Emmett–Teller and Barrett–Joyner–Halenda techniques. Finally, copper complexes of these ligands were employed in the synthesis of chiral allylic esters, achieving the best result with a 90% yield and 77% enantiomeric excess. Evaluation of the recyclability of the chiral heterogeneous catalysts revealed that they can be reused three times without a noticeable reduction in the results. In addition, the mechanism of formation of the chiral allylic esters was investigated using a density functional theory method.

Impacts of Five Different Drying Methods on Volatile Organic Compounds in Mulberry Fruits.

The mulberry fruit is edible and medicinal, and it is commonly referred to as the "best health product of the 21st century". The purpose of this study was to find out whether different drying methods affect the quality of mulberry fruits and the main nature of the volatile organic compounds (VOCs) they contain. This study used vacuum freeze-drying (VFD), vacuum drying (VD), sun drying (SD), hot-air drying (HAD), and microwave drying (MD) to treat fresh mulberry fruits. Gas-phase ion mobility spectrometry (GC-IMS) was used to detect and analyze the VOCs in mulberry fruit samples treated with the different drying methods. There were 47 VOCs detected, with aldehydes and alcohols dominating. The obtained data were subjected to principal component analysis (PCA), cluster analysis (CA), nearest neighbor fingerprint analysis, and partial least-squares regression analysis (PLS-DA). The conclusion was drawn that fresh mulberry fruits contain abundant VOCs, and mulberry fruits after VD contain many aldehydes; thus, VD promoted the synthesis of phellandrene and other compounds widely used in the preparation of cosmetics such as perfume and soap. HAD promoted the synthesis of esters commonly used in the preparation of fruit flavor and wine essence. The higher (E)-2-heptenal content with SD was conducive to the Maillard reaction. MD promoted the synthesis of heptanal and valeraldehyde with aroma characteristics such as fatty, green, fruity, grassy, and floral. According to the VIP results, VOCs (E)-2-heptenal, pentanal D, cyclohexanone, and 2-hexanone D influenced the VOCs in most of the mulberry fruit samples. The findings of this study provide an important reference for drying mulberry fruits, which, in turn, will help to ensure the safety and effectiveness of processed mulberry fruit products.

An improved synthesis of alkyl AMP esters

Enzymes belonging to the Acyl-CoA/NRPS/Luciferase (ANL) superfamily of enzymes, are significant targets in drug development. One member of this superfamily is Acetyl-CoA Synthetase (ACS). This enzyme is an emerging target for the treatment of various infectious diseases and cancer. Alkyl AMP esters have emerged as potent inhibitors of ACS. Previous methods for synthesizing these esters often involved water-based reactions or necessitate purification through reverse phase prep-HPLC or ion-exchange chromatography. To address these challenges, we developed a new approach utilizing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) to couple 5′-adenylic acid to the corresponding alcohol, utilizing triethylamine as the base. This method yielded primary, secondary, unsaturated, and cyclic alcohols in excellent yields. Importantly, we optimized the reaction conditions to achieve excellent yield and purity without the need for reverse phase prep-HPLC or ion exchange chromatography. Instead, purification was achieved through silica gel chromatography using Biotage ® Sfar spherical silica gel.

Photoinduced Radical Borylation of Robust Carbon–Heteroatom Bonds

AbstractPhotoinduced borylation has emerged as a valuable strategy for synthesizing arylboronic esters. However, photochemical transformations involving inert bonds such as C(sp2)−F bonds are still challenging. Herein, we report a straightforward and operationally simple method for the activation of various inert carbon–heteroatom bonds, enabling the synthesis of diverse arylboronic esters without the need for transition metals or catalysts. Mechanistic investigations reveal that the deprotonation of DMSO plays a pivotal role in the reaction, and the excited DMSO anion can undergo electron transfer to the aryl substrates activated by anionic sp2–sp3 diboron compounds, i. e., [FB2pin2]−, thereby facilitating the cleavage of carbon–heteroatom bonds. The reaction allows the conversion of diverse Caryl–hetero bonds in batch and flow reactors into the corresponding arylboronic esters. The products can be used in a subsequent Suzuki‐Miyaura cross‐coupling without isolation.

Design and Synthesis of Ester Linked 1,2,3‐Triazole Quinoline Derivatives with Pancreatic β Cells Protective Activity against Oxidative Stress and Endoplasmic Reticulum Stress for Better Management of Type II Diabetes Mellitus

AbstractUnresolved endoplasmic reticulum (ER) stress and oxidative stress lead to the pathogenesis of type II diabetes mellitus (DM). Connecting links between the ER stress and oxidative stress pathways might play an important role in treatment and pathogenesis of diabetes. Here, we used network pharmacology approach to find the target proteins linking the ER stress and oxidative stress pathways. CHOP emerged as a hub protein from our results and was targeted by 16 newly designed and synthesized ester linked 1,2,3‐triazole quinoline derivatives by molecular docking. Drug likeliness prediction studies revealed all compounds as good druggable candidates. Compounds 5b (R = H, R1 = F), 5j (R = CH3, R1 = F), 5m (R = OCH3, R1 = H), and 5n (R = OCH3, R1 = F) were found to have considerable binding energies and active site amino acid interactions with CHOP. We further showed that compounds 5b, 5m, and 5n exhibited low toxicity with more than 50% cell survival and low IC50 values. These were therefore subjected to evaluate their effects on ER stress and oxidative stress. Finally, compound 5n (R = OCH3, R1 = F) was found to alleviate ER stress and is also a good antioxidant. Identification of such targets and compounds effective in improving ER stress and oxidative stress may provide new insights in the development of therapies and management of T2DM.

Axially chiral α-boryl-homoallenyl boronic esters as versatile toolbox for accessing centrally and axially chiral molecules

Axially chiral allenes bearing organoboron groups are highly sought-after building blocks in organic synthesis due to their potential for generating a wide range of axially and centrally chiral molecules. However, the existing methods for preparing axially chiral allenes containing boron group are primarily limited to the synthesis of allenyl boronic esters, and strategies for accessing axially chiral homoallenyl boronic esters are still scarce. Here, we report the general method for synthesizing axially chiral α-boryl-homoallenyl boronic esters through a highly regio- and stereoselective copper-mediated SN2’-addition of newly prepared (diborylalkyl)copper species to chiral propargyl electrophiles. The reaction conditions were optimized to achieve high yields and excellent stereospecificity. The obtained products were successfully transformed into various axially chiral allenes and other chiral molecules by transforming diboron units. The potential for axial-to-central chirality transfer of axially chiral α-boryl-homoallenyl boronic esters is also demonstrated through the stereospecific addition to aldehydes and N-H aldimines, yielding enantioenriched 1,2-oxaborinin-3,5-dienes and 2-aminomethyl-1,3-dienes.

Enhanced stereodivergent evolution of carboxylesterase for efficient kinetic resolution of near-symmetric esters through machine learning

Carboxylesterases serve as potent biocatalysts in the enantioselective synthesis of chiral carboxylic acids and esters. However, naturally occurring carboxylesterases exhibit limited enantioselectivity, particularly toward ethyl 3-cyclohexene-1-carboxylate (CHCE, S1), due to its nearly symmetric structure. While machine learning effectively expedites directed evolution, the lack of models for predicting the enantioselectivity for carboxylesterases has hindered progress, primarily due to challenges in obtaining high-quality training datasets. In this study, we devise a high-throughput method by coupling alcohol dehydrogenase to determine the apparent enantioselectivity of the carboxylesterase AcEst1 from Acinetobacter sp. JNU9335, generating a high-quality dataset. Leveraging seven features derived from biochemical considerations, we quantitively describe the steric, hydrophobic, hydrophilic, electrostatic, hydrogen bonding, and π-π interaction effects of residues within AcEst1. A robust gradient boosting regression tree model is trained to facilitate stereodivergent evolution, resulting in the enhanced enantioselectivity of AcEst1 toward S1. Through this approach, we successfully obtain two stereocomplementary variants, DR3 and DS6, demonstrating significantly increased and reversed enantioselectivity. Notably, DR3 and DS6 exhibit utility in the enantioselective hydrolysis of various symmetric esters. Comprehensive kinetic parameter analysis, molecular dynamics simulations, and QM/MM calculations offer insights into the kinetic and thermodynamic features underlying the manipulated enantioselectivity of DR3 and DS6.

Preparation and Charcterisation of Acetate Cellulose Laurate Ester in Sodium Acetate/Zinc Chloride Systems

The objective of this study was to explore the preparation and characterisation of acetate cellulose laurate ester in sodium acetate/zinc chloride systems. The cellulose used in the study was obtained from oil palm empty fruit bunch and oil palm frond. The characterization of both the isolated cellulose and the acetate cellulose laurate ester was carried out using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Differential thermogravimetric (DTG), and Thermogravimetric analysis (TGA). The FT-IR analysis of the acetate cellulose laurate ester revealed the presence of C=O, confirming its modification. The crystallinity of the isolated cellulose and the acetate cellulose laurate ester was found to be 67-72% and 51-54%, respectively. The thermal stability of the isolated and modified cellulose esters was found to be 360-340 ℃ and 380-365 ℃, respectively. The solubility test showed that the prepared acetate cellulose laurate esters were soluble in different solvents. However, this study found that the synthesis of acetate cellulose laurate ester in an aqueous medium is not feasible. The improved hydrophobic character, good thermal stability, water retention value, and excellent solubility in different solvents of the acetate cellulose laurate ester reported in this study make it a potential material for applications in bioplastics, and packaging materials.

Screening appropriate lactic acid bacteria as adjunct starter to enhance characteristic flavor and sensory profiles of Huangjiu (Chinese rice wine)

Lactic acid bacteria (LAB) are crucial for enhancing Huangjiu flavor, yet no standardized criteria exist for selecting LAB strains for this purpose. This study aimed to investigate the suitability of screening appropriate LAB strains as adjunct starters for Huangjiu fermentation. Twenty-five LAB strains were assessed for their stress resistance and fermentation characteristics. Co-fermentation with Saccharomyces cerevisiae was conducted to explore its role in flavor development, as this yeast greatly contribute to desirable flavor profiles. Notably, Lactiplantibacillus plantarum AR1018, AR1026 and Weissella confusa AR1038 significantly reduced 3-methyl-1-butanol production while increasing levels of ethyl hexanoate and ethyl octanoate. These strains were selected for further analysis of their impact on the physicochemical properties, volatile organic compounds, and sensory attributes of Huangjiu. The LAB starters enhanced total acidity, sugar and protein utilization and ester synthesis, while reducing ethanol and alcohol levels. AR1018 achieved a 16.51% reduction in 3-methyl-1-butanol, whereas AR1038 exhibited a 27.32% increase in ester content compared to the control. Principal component analysis revealed distinct flavor characteristic between Huangjiu produced with AR1018 and AR1038, and sensory evaluation confirmed enhanced desirable attributes, especially for AR1038. This study highlights the potential of LAB starters in improving the flavor quality of rice wine and similar fermented beverages.

Silica‐Mediated Incorporation of Lipase Into The Bulk of a Deep Eutectic Solvent: An Efficient Biocatalytic Phase for Esters Synthesis

Aiming at sustainable solutions suitable for industrial‐scale catalysis catalytic phase containing lipase and Deep Eutectic Solvent (DES) was designed. To achieve this, both physical and chemical immobilizations of lipases were performed on the surface of silica and carbon materials. The catalytic activity of developed biosystem was tested in biotransformation of α‐angelica lactone into butyl levulinate at 60°C. The best results were achieved for Candida antarctica lipase B adsorbed on fumed silica suspended in choline chloride: glycerol (1:2) with the addition of 20 wt% of water. Under these conditions 99.9% conversion of α‐angelica lactone and 100% selectivity to butyl levulinate were obtained after 45 min. The biocatalytic system maintained its activity for up to five consecutive reaction cycles with full conversion of lactone to ester. The heterogenization of the enzyme allowed the biocatalyst to be integrated into the bulk of the DES, which includes essential water. This combination resulted in the formation of a stable and easy‐to‐operate catalytic phase where reagents formed a second organic phase. The integration of cost‐effective biocatalyst with process efficiency provides a greener alternative with significant potential for industrial use.

Synthesis of the Fatty Acid Ethyl Esters (FAEE) from Krabok (Irvingia malayana) Seed Oil for Use as the Main Ingredient in the Production of Herbal Massage Oil

This study focused on synthesizing fatty acid ethyl esters (FAEE) from Krabok (Irvingia malayana) seed oil via transesterification for use as the primary ingredient in herbal massage oil production. Optimal conditions included 5 wt.% of KOH catalyst compared to the oil weight, 15:1 molar ratio of ethanol to Krabok seed oil, 60 min for reaction time and reaction temperature of 78 ± 3 °C, resulting in FAEE yields as high as 99.83 ± 0.17 %. Analysis using FT-IR, 1H and 13C-NMR, and GC techniques revealed FAEE as ester-type compounds, primarily comprising lauric acid (C12:0) and myristic acid (C14:0), constituting 97 wt.% saturated fatty acids and 3 wt.% unsaturated fatty acids. Physicochemical properties indicated clear yellow liquids with viscosity of 1.73 ± 0.03 cSt/s, density of 0.8199 ± 0.0049 g/cm3, cloud point of +4 °C, and pour point of –1 °C. Acid value, free fatty acid content, iodine value, water content and oxidation stability were measured at 0.703 ± 0.001 mg KOH/g of oil, 0.354 ± 0.001 wt.%, 0.59 ± 0.04 g I2/100 g of oil, 1482.3 ± 6.15 ppm, and greater than 12 h, respectively. When the synthesized FAEE was used to produce herbal massage oil products, the results showed that the herbal massage oil products were characterized as a clear yellow liquid with no sediment, low viscosity, and pH in the range of 5 - 6, meeting standard criteria. Thus, FAEE derived from Krabok seed oil is suitable as a primary ingredient for herbal massage oil production, enhancing the value of local resources within the community. HIGHLIGHTS Under optimal conditions of 5 wt.% KOH catalyst, 15:1 ethanol to oil ratio, 60 min at 78 ± 3 °C, FAEE was synthesized from Krabok seed oil for herbal massage oil, yielding 99.83 ± 0.17 %. FAEE, identified via FT-IR, 1H and 13C-NMR, and GC, comprises 97 wt.% saturated fatty acids (lauric acid and myristic acid) and 3 wt.% unsaturated. The herbal massage oil derived from FAEE as the primary ingredient meets clarity, low viscosity, and pH 5 - 6 standards. FAEE from Krabok seed oil enhances the value of local resources. GRAPHICAL ABSTRACT

Bcwf regulates the white petal color in pak choi [Brassica campestris (syn. Brassica rapa) ssp. chinensis]

Flower color is important in determining the ornamental value of Brassica species. However, our knowledge about the regulation of flower color in pak choi [Brassica campestris (syn. Brassica rapa) ssp. chinensis] is limited. In this study, we investigated the molecular mechanism underlying white flower traits in pak choi by analyzing a genetic population with white and yellow flowers. Our genetic analysis revealed that the white trait is controlled by a single recessive gene called Bcwf. Through BSA-Seq and fine mapping, we identified a candidate gene, BraC02g039450.1, which is similar to Arabidopsis AtPES2 involved in carotenoid ester synthesis. Sequence analysis showed some mutations in the promoter region of Bcwf in white flowers. Tobacco transient assay confirmed that these mutations reduce the promoter's activity, leading to downregulation of Bcwf expression in white flowers. Furthermore, the silencing of Bcwf in pak choi resulted in lighter petal color and reduced carotenoid content. These findings provide new insights into the molecular regulation of white flower traits in pak choi and highlight the importance of Bcwf in petal coloring and carotenoid accumulation.

Lipase Substrate Anchoring Dynamics Guided the Rational Design of Novel Deep Eutectic Solvents for Glucose Ester Synthesis.

Glucose esters, heralded for their emulsifying and solubilizing properties, have found increasing application in food, pharmaceutical, and cosmetic sectors. However, the environmental impact of chemical synthesis and the problem of enzyme inactivation in enzymatic synthesis have hindered their application. To this end, deep eutectic solvents (DESs) with stabilized enzyme activity and better solubility properties are considered a promising solution. In the study, 12 kinds of hydrophilic DESs and 22 kinds of hydrophobic DESs were screened, and we examined their efficiency in the synthesis of glucose esters. The results indicated that d,l-menthol-based DESs have excellent performance, with the highest yield of 92.85%. The molecular dynamics simulations suggested that it can be attributed to DESs changing the size of substrate binding pocket, which in turn affects the substrate anchoring ability and the catalytic efficiency of lipase. To further evaluate the effects of the solvent on the substrate anchoring ability of enzymes, a novel strategy, namely, substrate anchoring index, which is based on the stability of the tetrahedral intermediate, was proposed and used for the designing of more efficient DESs. Fortunately, novel DESs based on cyclohexanone (menthol analogues) were successfully developed with a yield of 98.85%.

Amino-Alkyl Group Dual-Functional Modification Synergistically Regulated Lipase-Carrier Interactions and Enhanced Phytosterol Ester Synthesis Efficiency.

Precisely controlling enzyme conformation to enhance catalytic performance is a highly sought-after yet challenging goal in the immobilization of biocatalysts. Excessively strong enzyme-carrier interactions can restrict enzyme dynamics and reduce catalytic efficiency, while excessively weak interactions may lead to enzyme leakage, thereby reducing reusability. In this study, we developed a novel strategy to finely regulate the interaction between the carrier and the enzyme through the adjustment of the ratio of amino and octadecyl functional groups. The expressed activity of the novel immobilized lipase, CRL@AOMR, was 1.32- and 2.34-fold higher than that of the monofunctional macroporous resin. Moreover, the synthesis of various phytosterol esters in solvent-free systems was conducted as a model reaction to investigate the utilization of CRL@AOMR in different reactions. Under optimized conditions, an impressive yield of 96.1% for phytosterol oleate was achieved and a yield of 76.2% was maintained even after six cycles of utilization (288 h). This study demonstrates the potential feasibility of developing immobilization strategies via dual modification of amino and alkyl groups, which is a potential general strategy for other enzymes with surface lysine.

Exploring Community Succession, Assembly Patterns, and Metabolic Functions of Ester-Producing-Related Microbiota during the Production of Nongxiangxing baijiu.

Esters are vital flavor compounds in Chinese Nongxiangxing baijiu and greatly affect the quality of baijiu. Microbial communities inhabiting fermented grains (FGs) have a marked impact on esters. However, the specific microorganisms and their assembly patterns remain unclear. This study utilized high-throughput sequencing and a culture-based method to reveal ester-producing microorganisms. A total of 33 esters were detected, including 19 ethyl esters, 9 linear chain esters, and 2 branched chain esters. A correlation analysis indicated that the bacterial genus Lactobacillus (relative abundance in average: 69.05%) and fungal genera Pichia (2.40%), Aspergillus (11.84%), Wickerhamomyces (0.60%), Thermomyces (3.57%), Saccharomycopsis (7.87%), Issatchenkia (0.96%), and Thermoascus (10.83%) were dominant and associated with esters production and their precursors. The numbers of esters positively correlated with them were 1, 17, 3, 2, 1, 1, 1, and 1, respectively. The modified stochasticity ratio (MST) index and Sloan neutral model revealed that bacteria were predominantly governed by deterministic processes while fungal assemblies were more stochastic. Saturnispora silvae and Zygosaccharomyces bailii were isolated and identified with ester synthesis potential. PICRUSt2 analysis showed that fungi in FG had a high potential for synthesizing ethanol, while 14 enzymes related to esters synthesis were all produced by bacteria, especially enzymes catalyzing the synthesis of acyl-CoA. In addition, ester synthesis was mainly catalyzed by carboxylesterase, acylglycerol lipase and triacylglycerol lipase. These findings may provide insights into ester production mechanism and potential strategies to improve the quality of Nongxiangxing baijiu.

Synthesis and evaluation of esters obtained from phenols and phenoxyacetic acid with significant phytotoxic and cytogenotoxic activities.

There is a growing demand for herbicides that are more effective than conventional ones yet less harmful to ecosystems. In light of this, this study aimed to synthesize esters from phenols and phenoxyacetic acid, using compounds with known phytotoxic potential as starting materials. Phenoxyacetic acid was first synthesized and then utilized in the synthesis of seven esters through Steglich esterification, employing N,N'-dicyclohexylcarboimide and N,N-dimethylpyridin-4-amine in the presence of phenols (thymol, vanillin, eugenol, carvacrol, guaiacol, p-cresol, and β-naphthol), yielding esters 1-7. All synthesized compounds were characterized using mass spectrometry, 1H, and 13C NMR. These compounds were tested for phytotoxicity to evaluate their effects on the germination and root development of Sorghum bicolor and Lactuca sativa seeds, and for the induction of alterations in the mitotic cycle of meristematic cells of L. sativa roots. Esters 1, 3, 4, and 5 exhibited the most significant phytotoxic activity in both L. sativa and S. bicolor. Alterations in the mitotic index and frequency of chromosomal alterations in L. sativa roots revealed the cytotoxic, genotoxic effects, and the aneugenic mode of action of the tested molecules. These findings suggest that these compounds could serve as inspiration for the synthesis of new semi-synthetic herbicides.

Lawesson’s reagent in the synthesis of a malic ester of dithiophosphonate salts with antifungal activity

Lawesson’s reagent reacted with racemic diethyl malate to yield O-(1,2-bis(ethylcarboxylate)ethyl-1 4-methoxyphenyl dithiophosphonic acid. The acid formed pyridinium dithiophosphonate salts with 3-(hydroxymethyl)pyridine, pyridoxine, and (S)-(–)-nicotine. The salts revealed antifungal activity against Candida albicans.

Enzymatic synthesis of vanillyl fatty acid esters from salmon oil in a solvent-free medium

This study hypothesizes that the solvent-free alcoholysis of oil recovered from salmon heads using vanillyl alcohol (VA) and immobilized lipase B can efficiently produce esters with enhanced stability and antioxidant properties. The objective was to investigate the selectivity and resulting ester profile, which may provide nutritional and functional advantages compared to supplementing oil with vanillyl alcohol. After 24 h, nearly complete conversion of vanillyl alcohol was achieved, leading to the production of various esters reflective of the oil's original fatty acid composition. The synthesis of esters like oleoyl and linolenoyl was favored over docosahexaenoyl and linoleoyl esters, influenced by fatty acid distribution and enzyme specificity, along with potential intra-molecular acyl transfer isomerization. The reaction medium demonstrated significant stability and antioxidant activity, highlighting the potential benefits of vanillyl esters over traditional supplementation methods. These findings suggest that the phenolic alcohol-based alcoholysis of fish oil offers a promising approach to generating stable, nutritionally valuable extracts with potent antioxidant capabilities.

Ethyl esters synthesis catalyzed by lipase B from Candida antarctica immobilized on NiFe2O4 magnetic nanoparticles

Ethyl esters synthesis catalyzed by lipase B from Candida antarctica immobilized on NiFe2O4 magnetic nanoparticles