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Determining the structure and phenotypic context of molecules detected in untargeted metabolomics experiments remains challenging. Here we present reverse metabolomics as a discovery strategy, whereby tandem mass spectrometry spectra acquired from newly synthesized compounds are searched for in public metabolomics datasets to uncover phenotypic associations. To demonstrate the concept, we broadly synthesized and explored multiple classes of metabolites in humans, including N-acyl amides, fatty acid esters of hydroxy fatty acids, bile acid esters and conjugated bile acids. Using repository-scale analysis1,2, we discovered that some conjugated bile acids are associated with inflammatory bowel disease (IBD). Validation using four distinct human IBD cohorts showed that cholic acids conjugated to Glu, Ile/Leu, Phe, Thr, Trp or Tyr are increased in Crohn's disease. Several of these compounds and related structures affected pathways associated with IBD, such as interferon-γ production in CD4+ T cells3 and agonism of the pregnane X receptor4. Culture of bacteria belonging to the Bifidobacterium, Clostridium and Enterococcus genera produced these bile amidates. Because searching repositories with tandem mass spectrometry spectra has only recently become possible, this reverse metabolomics approach can now be used as a general strategy to discover other molecules from human and animal ecosystems.

BackgroundWidespread exposure to organophosphate ester (OPE) flame retardants with potential reproductive toxicity raises concern regarding the impacts of gestational exposure on birth outcomes. Previous studies of prenatal OPE exposure and birth outcomes had limited sample sizes, with inconclusive results.ObjectivesWe conducted a collaborative analysis of associations between gestational OPE exposures and adverse birth outcomes and tested whether associations were modified by sex.MethodsWe included 6,646 pregnant participants from 16 cohorts in the Environmental influences on Child Health Outcomes (ECHO) Program. Nine OPE biomarkers were quantified in maternal urine samples collected primarily during the second and third trimester and modeled as log2-transformed continuous, categorized (high/low/nondetect), or dichotomous (detect/nondetect) variables depending on detection frequency. We used covariate-adjusted linear, logistic, and multinomial regression with generalized estimating equations, accounting for cohort-level clustering, to estimate associations of OPE biomarkers with gestational length and birth weight outcomes. Secondarily, we assessed effect modification by sex.ResultsThree OPE biomarkers [diphenyl phosphate (DPHP), a composite of dibutyl phosphate and di-isobutyl phosphate (DBUP/DIBP), and bis(1,3-dichloro-2-propyl) phosphate] were detected in >85% of participants. In adjusted models, DBUP/DIBP [odds ratio (OR) per doubling=1.07; 95% confidence interval (CI): 1.02, 1.12] and bis(butoxyethyl) phosphate (OR for high vs. nondetect=1.25; 95% CI: 1.06, 1.46), but not other OPE biomarkers, were associated with higher odds of preterm birth. We observed effect modification by sex for associations of DPHP and high bis(2-chloroethyl) phosphate with completed gestational weeks and odds of preterm birth, with adverse associations among females. In addition, newborns of mothers with detectable bis(1-chloro-2-propyl) phosphate, bis(2-methylphenyl) phosphate, and dipropyl phosphate had higher birth weight-for-gestational-age z-scores (β for detect vs. nondetect=0.04-0.07); other chemicals showed null associations.DiscussionIn the largest study to date, we find gestational exposures to several OPEs are associated with earlier timing of birth, especially among female neonates, or with greater fetal growth. https://doi.org/10.1289/EHP13182.

Comprehensive Summary The EDA complex‐mediated reactions involving oxime esters have been few studied. Herein, an EDA complex formed by thiophenolate anion and oxime ester is reported for photoinduced divergent synthesis of thioethers, depending on different types of oxime esters. Operational simplicity, mild reaction conditions, and flexible options of leaving group demonstrate the generality and synthetic utility of this approach. Such an approach can also enable an interesting thiol‐catalysis for the synthesis of phenanthridines. [ABSTRACT FROM AUTHOR]

Comprehensive Summary The EDA complex‐mediated reactions involving oxime esters have been few studied. Herein, an EDA complex formed by thiophenolate anion and oxime ester is reported for photoinduced divergent synthesis of thioethers, depending on different types of oxime esters. Operational simplicity, mild reaction conditions, and flexible options of leaving group demonstrate the generality and synthetic utility of this approach. Such an approach can also enable an interesting thiol‐catalysis for the synthesis of phenanthridines. [ABSTRACT FROM AUTHOR]

The irreversible locking of reversible imine linkages in COFs into quinoline-4-carboxylic esters has been achieved for the first time through the Doebner–von Miller reaction. The high conversion efficiency and broad scope were demonstrated by synthesizing four quinoline-4-carboxylic ester-linked COFs (QCE-COFs). Subsequently, this approach was applied to create the chiral QCE-COF-Men containing L -menthol. Remarkably, QCE-COF-Men was found to release the flavorant L -menthol at elevated temperature by cleaving the weak ester bond without destroying the quinoline skeleton. [ABSTRACT FROM AUTHOR]

A simple and efficient three‐component coupling reaction of carboxylic acids, diazo compounds, and tertiary amines catalyzed by manganese has been described. This reaction proceeds smoothly under mild conditions to afford various β‐amino esters in moderate to good yields by using O2 as the terminal oxidant. In this process, Mn‐based carbene radical, single‐electron transfer, and nucleophilic attack were fused into a reaction system. [ABSTRACT FROM AUTHOR]

The Yamaguchi reagent, based on 2,4,6-trichlorobenzoyl chloride (TCBC) and 4-dimethylaminopyridine (DMAP), is an efficient tool for conducting the intermolecular (esterification) reaction between an acid and an alcohol in the presence of a suitable base (Et3N or iPr2NEt) and solvent (THF, DCM, or toluene). The Yamaguchi protocol is renowned for its ability to efficiently produce a diverse array of functionalized esters, promoting high yields, regioselectivity, and easy handling under mild conditions with short reaction times. Here, the recent utilization of the Yamaguchi reagent was reviewed in the synthesis of various natural products such as macrolides, terpenoids, polyketides, peptides, and metabolites. [ABSTRACT FROM AUTHOR]

Interactions between lone pairs and aromatic π systems are significant across biology and self‐assembled materials. Herein, employing an achiral confinement metal–organic framework (MOF) encapsulates guest molecules, it is successfully realized that lone pair (lp)‐π interaction induces fluorescence "turn‐on" and circularly polarized luminescence for the first time. The MOFs synthesized based on naphthalenediimide show nearly non‐emissive, which can be light‐up by introducing acetone or ester guests containing lone pairs‐π interaction. Furthermore, the introduction of a series of lp‐rich chiral esters induces supramolecular chirality as well as circularly polarized luminescence in achiral MOFs, while also observing chiral adaptability. This work first demonstrates the luminescence and chiral induction via lone pair electrons‐π interactions, presenting a fresh paradigm for the advancement of chiroptical materials. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of functionalized three-dimensional benzophenone analogues derived from [2.2]paracyclophane (pCp). The potential use of these compounds as photocatalysts is disclosed. Benzophenone and its derivatives are well-known photoactive compounds that have been extensively employed over the years as catalysts to promote a variety of transformations activated by light. The development of differently substituted three-dimensional versions of such compounds may significantly expand the range of their applications in photocatalysis. Exploitation of the planar chirality of substituted paracyclophanes may also lead to significant innovations in different fields. [2.2]Paracyclophane-based benzophenone derivatives incorporating reactive ester or amide functions at their pseudo-gem position are successfully prepared in a selective manner. Examples of both racemic and enantiopure compounds are reported. As a proof of concept, the catalytic activities of the newly synthesized molecules are compared to that of benzophenone in a known photooxidation reaction. [ABSTRACT FROM AUTHOR]

Cu/SiO2 catalysts are widely applied to the hydrogenation of dimethyl oxalate and ethylene carbonate to the corresponding ethylene glycol and methanol simultaneously, whereas ethylene glycol and methanol are important bulk commodities and raw materials for the production of oxygen‐containing chemicals and fuels. However, Cu particles usually aggregate or sinter to deactivate and the ratio of surface Cu0/Cu+ species is also difficult to control under the reaction conditions, so that the catalyst activity and stability is still a big challenge. It was found that modification of Cu‐based catalysts with certain organic compound inhibited the agglomeration of Cu particles, regulated the ratio of surface Cu0/Cu+ species, and even generated carbon layers to protect the Cu particles, which definitely improved the stability of the catalyst along with the enhanced catalytic performance. In this review, recent developments in ester hydrogenation over organic compound‐modified Cu/SiO2 catalysts were summarized and the issues to be further clarified are discussed as well. [ABSTRACT FROM AUTHOR]

Herein we describe an efficient methodology for metal‐free hydroborative cleavage of lactones and esters with HBPin (Pin=pinacol) to the corresponding alcohol derivatives using ammonia borane as a pre‐catalyst. The reactions proceed under mild conditions, can be performed in a solvent‐free manner, and do not require an inert atmosphere. Combined experimental and computational mechanistic studies suggest a novel mechanism that involves μ‐aminodiboranes as catalytically active species. [ABSTRACT FROM AUTHOR]

Development of new organic synthetic methods fascinating the researchers which facilitating the increasing demands of the modern society, environmental friendly with high efficiency and low cost. The introduction of chromophores in an organic molecules facilitating intersystem crossing (ISC) to harvest both singlet and triplet excitons is also currently demanding field. We report a facile synthesis of symmetrical azines from carbonyl compounds and hydrazine hydrate with carboxylic acid esters as catalyst in methanol. This reaction presents a condensation of primary amino groups in hydrazine hydrate and carbonyl compounds took place simultaneously in a very short refluxing time. The prepared azines 1–10 were structurally analysed by various analytical techniques such as LC-MS1, H NMR13, C NMR, UV-Vis, FTIR and single crystal X-ray diffraction. Photoluminescence properties of prepared azines were recorded in CCl4 at 1 × 10−3 M and excitation range from 329 to 362 nm. The photoluminescence analysis results revealed that compounds 1–10 (except 8) were showed delayed fluorescence and 8 was showed fluorescence property. The photophysical properties of compounds 1–10 such as electron density and band gap energies was calculated by density function theory. This results revealed that the intra-molecular charge transfer occurs within the azines. The azine function in the azines enabling intersystem crossing hence, it is showing phosphorescence. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. Carboxylesterases catalyze the enantioselective synthesis of chiral carboxylic acids and esters but exhibit limited enantioselectivity, particularly toward ethyl 3-cyclohexene-1- carboxylate (CHCE). Here, the authors establish a high-throughput method to generate a high-quality dataset for carboxylesterase AcEst1 from Acinetobacter sp. JNU9335 using CHCE as the substrate, use it to train a machine learning predictor and design two stereocomplementary mutants to synthesize both enantiomers of chiral CHCE. [ABSTRACT FROM AUTHOR]

Acyl iodides are expected to be excellent acylating agents due to the low bond dissociation energy of the carbon–iodine bond and the high capability of iodine as a leaving group. Unfortunately, the preparative methods for acyl iodides directly from carboxylic acids are rather limited. In this work, we found that a novel binary system combining I2 and diphenylphosphine oxide (Ph2P(O)H) provides a simple method for the preparation of acyl iodides from carboxylic acids. Furthermore, the subsequent one‐pot reaction with appropriate nucleophiles, such as amines, alcohols, and thiols, afforded the corresponding amides, esters, and thioesters, respectively, in good to excellent yields. [ABSTRACT FROM AUTHOR]

Efficient approaches toward the synthesis of quinazolines and dihydroisoquinolines have been developed through copper‐catalyzed aerobic oxidative dehydrogenation of N‐heterocycles. The dehydrogenation was achieved through copper‐catalyzed aerobic oxidative dehydrogenation and azodicarboxylate esters‐mediated dehydrogenation of amines. Azodicarboxylate esters could be regenerated from copper‐catalyzed dehydrogenation of corresponding hydrazodicarboxylate esters, which made this catalytic dehydrogenation process more efficient and reactive. [ABSTRACT FROM AUTHOR]

Herein the one‐pot thioesterification and hydrothiolation of α, β‐unsaturated esters with aliphatic thiols was reported at room temperature. The mechanism was indirectly revealed which α, β‐unsaturated thioester was the intermediate. The advantages of this method included transition‐metal‐free, mild conditions, broad substrate scope and good functional group tolerance. On the other hand, the hydrothiolation of α, β‐unsaturated aliphatic esters at room temperature was also developed. [ABSTRACT FROM AUTHOR]

Comprehensive Summary A tandem Diels–Alder reaction/Claisen rearrangement/decarboxylation strategy of N‐allenamides (or aryloxyallenes) with 3‐alkoxycarbonyl‐2‐pyrones has been developed for the efficient synthesis of diarylmethanes with moderate to good yields. The reaction exhibits good functional group tolerance and can be applied to late‐stage modifications of known drug molecules. Mechanistic studies indicate that the ester group at the 3‐position of 2‐pyrones is essential, and the initial Diels–Alder reaction between the 2‐pyrones and the proximal C=C bond of the N‐allenamides (or aryloxyallenes) is crucial for the success of the reaction. [ABSTRACT FROM AUTHOR]

There is need for advancing minimally invasive diagnostic techniques for sex differentiation at early life-stage classes in sea turtles. The objectives of this study were to determine whether there are sex-specific effects on the metabolome of the loggerhead sea turtle (Caretta caretta) and to identify potential biomarkers for sex classification at early life-stage classes (50 post-hatchling and 50 juvenile). Comprehensive analyses including plasma chemistry (n = 100) and untargeted (n = 48) metabolomic analyses were performed. Unlike with plasma chemistry analytes, there were significant differences in the metabolomic profiles between sexes. Nine metabolites differed significantly between sexes, with several metabolites deserving greater attention as potential biomarkers: C22H32O6 and pantothenic acid was higher in females than in males, and carboxylic acid ester (C10H16O5), 1-methylhistidine and C7H14N2O7 was higher in males than females. These differences remained constant both across and within the same life-stage class. This work identified a discernible effect on the metabolic profile based on sex of loggerhead sea turtles and it suggests that these metabolites and/or their ratios could serve as potential biomarker candidates for sex classification in this species. This study demonstrates a distinct metabolomic profile between male and female loggerhead turtles at different physiological stages (posthatchling and juvenile animals) and proposes biomarkers for sex classification. [ABSTRACT FROM AUTHOR]

An efficient one-step procedure for the synthesis of a new series of multifunctional olefins by condensation of α-substituted β-diketones as well as β-phosphonoesters and benzoylated β-ketoesters with formaldehyde, using potassium carbonate in refluxing THF, followed by a deacylation reaction, is herein described. In contrast, the α-substituted β-keto esters, bearing an acyl moiety, only undergo a hydroxymethylation reaction, with no metal catalysts/activating agents, as is usually required for the process, affording the corresponding α-hydroxymethyl β-keto esters in high yields. [ABSTRACT FROM AUTHOR]

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A simple and efficient strategy has been developed for the synthesis of organic nitrate esters via visible‐light‐induced multi‐component nitrooxylation reactions of α‐diazoesters, cyclic ethers, and tert‐butyl nitrite under open air atmosphere. This transformation could be conducted under mild and metal‐free conditions to provide a number of organic nitrate esters in moderate to good yields using air as the green oxidant. [ABSTRACT FROM AUTHOR]

A ZnO‐mediated benzoylation between carvone oxime and acyl is reported, enabling access to diverse carvone oxime ester and carvone oxime sulfonic esters under solvent‐free conditions. The operationally simple procedure provides a novel method for the synthesis of oxime‐ester bonds with excellent chemo selectivity. This strategy provides a mild, direct, and green approach for synthesizing carvone oxime ester in moderate to excellent yields with good substrate tolerance. In addition, carvone oxime was synthesized under solvent‐free conditions. [ABSTRACT FROM AUTHOR]

We disclose herein a triflic acid and silane‐promoted reductive deoxygenative transformation of ketoacid/esters for the divergent synthesis of different‐sized lactones, which hold substantial significance in pharmaceutical and natural product chemistry. Owing to the simple reaction conditions and setup, this protocol features broad substrate generality, scalability, and good functional group tolerance, including late‐stage functionalization of pharmaceutical compounds and natural products. The control experiments and detailed NMR study provide insight into the reaction mechanism. [ABSTRACT FROM AUTHOR]

A mild, metal‐free Giese‐type hydrodifluoroalkylation of electron‐deficient alkenes under visible‐light irradiation has been developed. This highly reducing photoactivated Hantzsch ester facilitates C(sp3)−CF2 bond formation through photoinduced electron transfer (PET) and hydrogen atom transfer (HAT) processes, providing an easy access to diverse gem‐difluorinated alkanes. [ABSTRACT FROM AUTHOR]

Readily accessible (PSi)Ni(II)‐benzyl complexes supported by bidentate phosphino(silyl) ligation were found to be effective pre‐catalysts for the direct hydrogenation of a variety of highly sterically hindered, unfunctionalized alkenes under relatively mild conditions (2.5‐5 mol% Ni, 10 atm H2, 50 °C) and without the need for additional additives or activator species. A range of substrates, including di‐, tri‐, and tetra‐substituted alkenes were evaluated in this regard and afforded good to moderate yields. Substrates featuring α,β‐unsaturated carbonyl functionality were also readily hydrogenated with no evidence for reduction of carbonyl or ester C−O functionalities. Deuteration experiments highlight the occurrence of chain walking which occurs in the background of the reported catalytic chemistry. [ABSTRACT FROM AUTHOR]

Current routes to boronic acids and their corresponding esters to be used in subsequent Suzuki–Miyaura (SM) cross couplings impact the cost, waste, and safety concerns associated with generating these materials. A new method for installing the ethyl pinacol boronic ester, or B(Epin) derivative leads to stable borylated products under near-neat conditions using high concentrations of a green solvent and moderate reaction temperatures, catalyzed by relatively low palladium loadings. Alternatively, the newly fashioned Ar–B(Epin) can be generated in situ and used directly in the same pot for SM reactions leading to aromatic and heteroaromatic residues characteristic of the biaryl products being formed. An array of complex targets, including API-related products, can be generated via this green and environmentally responsible methodology. [ABSTRACT FROM AUTHOR]

We report the first switchable acylation of H-phosphonate with chloroformate. The acylation site (P vs. O) in H-phosphonate was switched by changing the acyl pyridinium/ammonium ions. Unexpected phosphite formation was observed during the O-acylation of H-phosphonate. Twenty-six structurally diverse phosphotriesters and phosphonoformate esters were synthesized in microflow reactors. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the current study, we attempt to remove 3‐monochloropropane‐1,2‐diol fatty acid ester (3‐MCPD ester) from palm oil with developed composite adsorbent (Tween80 modified activated carbon [AC]), and scanning electron microscopy‐energy dispersive spectrometer, Fourier transform‐infrared spectroscopy, X‐ray diffraction, nitrogen content adsorption‐desorption and thermogravimetric analysis were used to characterize the modifications. We further examined the adsorption capability of the composite adsorbent for 3‐MCPD ester and found that the highest removal efficiency was 87.36% (5.3% of adsorbent dose at 104°C for 29 min). This is approximately three times higher than that of pristine AC, implying that the composite can be employed as a novel adsorbent for 3‐MCPD ester reduction. Along with the adsorption mechanism of Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin models were also tested. It has been suggested that Freundlich model could best describe the adsorption process. Adsorption was found to be well‐fitted by pseudo‐second‐order kinetics according to the kinetic study. An endothermic and spontaneous adsorption mechanism was demonstrated by the thermodynamic studies. [ABSTRACT FROM AUTHOR]

A metal-free strategy has been developed for the α-arylation of carboxylic acids, secondary amides, and esters employing arenes as key reagents. This process entails the Lewis-acid catalyzed reductive Friedel–Crafts alkylation of arenes utilizing α-ketoacids, facilitated by silane in HFIP solvent. The transformation exhibits exceptional functional group tolerance, enabling late-stage functionalization of natural products. This one-step protocol has been successfully used to synthesize commercially available drugs, such as adiphenine, piperidolate, derivatives of ketoprofen, ibuprofen, flurbiprofen, and the pesticide bromopropylate. [ABSTRACT FROM AUTHOR]

This study involves the synthesis of asterism compounds (D1-D6) through the reaction of 1 mole of benzene 1,3,5-triol with 3 moles of prepared pentacyclic ring ester derivatives, dissolved in absolute ethanol. The validity of the compound structures was confirmed using physical and spectroscopic methods such as infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy. Additionally, melting points and purity were determined, and reaction progress was monitored by Thin-Layer Chromatography (TLC). The liquid crystal phases of certain prepared compounds were examined using a polarizing optical microscope (POM). [ABSTRACT FROM AUTHOR]

Poria cocos (Schw.) wolf (P. cocos) is an important medicinal material with both therapeutic and edible properties. This study investigated volatile constituents, amino acids, proteins, polysaccharides, triterpenoid ingredients, and alcohol-soluble extracts on P. cocos during eight drying processes. A total of 47 volatile components were found and identified; the main volatile components of shade drying (SD) and hot-air drying at 50 °C (HD50) were esters and alcohols, while for drying in hot air at 60 °C~100 °C (△ = 10 °C) and infrared drying (ID), the main compounds were aldehydes and hydrocarbons. The amino acids in P. cocos remained the same when dried with various methods. Compared with SD samples, with the temperature increase, the content of amino acids showed a trend of first decreasing and then increasing, while the content trend of proteins was the opposite. The HD70 samples had the highest content of polysaccharide, triterpenoid ingredients, alcohol-soluble extracts, and antioxidant activity. Furthermore, volatile compounds showed a correlation between non-volatile constituents. This research provides evidence that the aroma, active components, and activity of P. cocos were affected by the drying method. [ABSTRACT FROM AUTHOR]

Epothilones are 16‐membered macrolides that act as microtubule‐targeting agents to tackle cancer. Many synthetic analogues have been investigated for their activity, yet often based on macrolide structures. A notable exception is Ixabepilone, an azalide whose metabolic stability and pharmacokinetics are significantly improved. Exploiting the amide‐triazole bioisosterism, in this work we report the synthesis of the first generation of epothilones lacking the macrolide or azalide structure, with the ester or amide linkage replaced by a triazole unit. Together with the synthesis of this new analogue, computational and biological evaluations have been performed too. [ABSTRACT FROM AUTHOR]

This study examines and compares the breakdown and aging properties of five insulating liquids. Additionally, the influence of different voltage polarities on these properties was analyzed to investigate the effect of aging on polarity behavior under lightning impulse voltage in a semi-uniform field. The results were compared to standardized AC breakdown tests. After 2330 h and 4350 h of aging, changes were observed in key aging indicators such as water content (both absolute and relative), total acid number, and color across all liquids. Viscosity increased by up to 10% in natural esters. Notably, the rise in water content due to aging was concerning only for mineral oil, exceeding 20%. The impact of aging on breakdown voltage varied depending on the voltage type and polarity. Aging had the least effect under negative lightning impulse voltage, while the synthetic ester MIDEL 7131 exhibited the most significant reduction in breakdown voltage under positive lightning impulse voltage, dropping by over 24%, from more than 560 kV to 428 kV. In contrast, mineral oil showed only a 3% decrease. For the other liquids, the most pronounced reduction in breakdown voltage due to aging occurred under AC voltage, with natural esters showing a 17% decline, synthetic esters 26%, and mineral oil experiencing a 38% reduction. [ABSTRACT FROM AUTHOR]

In this study, a difluorocarbene‐promoted O−O bond activation of peroxy acids is developed through the insertion of difluorocarbene into O−H bond. This activation strategy in synergy with O−B coordination with boronic acids/ester greatly polarizes the O−O bond for in‐situ generation of carboxylium species that reacts with the nucleophilic part of boronic acids in a concerted way to produce carboxylic esters. Good efficiency and functional group tolerance are demonstrated. Application of this method to the functionalization of a boronic acid drug used as HSL enzyme inhibitor produces smoothly the ester derivative. This difluorocarbene‐mediated O−O bond activation strategy is conceptually different from traditional radical type methods, and is also complementary to conventional esterification methods with a distinct retro‐synthetic disconnection. [ABSTRACT FROM AUTHOR]

The selective functionalization of 1,3-bis(boronic) esters holds the potential for creating diverse molecular structures, particularly through the late-stage functionalization of the remaining C–B bond. By employing distinct organometallic reagents, we have developed a method for regiodivergent alkynylation of 1,3-bis(boronic) esters, facilitated by unique chelation patterns. Notably, this methodology effectively overcomes limitations commonly encountered in radical chemistry, which generates only monoselective downstream targets. Furthermore, the compounds synthesized through this approach can serve as significant building blocks, contributing to the construction of molecular complexity. [ABSTRACT FROM AUTHOR]

Metal triflate-catalyzed acylation of sulfonamides and direct transacylation of N-acylsulfonamides have been investigated. The acylation of sulfonamides proceeds efficiently in the presence of a catalytic amount of Cu(OTf)2 (0.001 equiv) using either carboxylic anhydrides or acyl chlorides as the acylating agents. Alternative catalysts suitable for this transformation include Al(OTf)3, Fe(OTf)3, Ga(OTf)3, In(OTf)3, and Er(OTf)3. In the presence of Cu(OTf)2 (0.2 equiv), N-acylsulfonamides undergo direct transacylation in excess acyl chlorides (10 equiv) to furnish new N-acylsulfonamides through exchange of N-acyl groups. Ga(OTf)3, Fe(OTf)3, and In(OTf)3 are similarly reactive in catalyzing such transacylation transformations. The reaction conditions are mild and operationally convenient. A variety of functional groups including halogeno, keto, nitro, cyano, ether, and carboxylic ester are tolerated, providing the corresponding monoacylated N-acylsulfonamides in good to excellent yields. [ABSTRACT FROM AUTHOR]

Coffee is one of the most highly valued, consumed and comercialized foods in the world. Due to its considerable importance, it has become the target of numerous adulterations. Detecting a possible adulteration and the presence of additional adulterants in coffee has become an issue of great concern mainly because the compounds used as adulterants exhibit physical features very similar to ground roasted coffee. Aiming to overcome these difficulties, this work reports the development and application of a relatively faster, highly effective and reliable method for the detection and identification of adulterations in roasted coffee through the analysis of the composition of the volatile fraction in the presence of adulterants such as rice, corn, soybeans and barley. The proposed method was based on gas chromatography coupled with mass spectrometry (GC–MS) and chemometric tools. The application of the method led to the exclusive identification of many compounds in the volatile fraction of the adulterants investigated. The adulterants, despite having compounds similar to coffee, differed in terms of their volatile profiles, and consisted mainly of hydrocarbons, aldehydes, esters and carboxylic acids. Among all the compounds identified, five compounds were found to be the main determinants of adulteration: 2-furanmethanol-acetate, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 2-furanmethanol and glycerol-1,2-diacetate. [ABSTRACT FROM AUTHOR]

Recently, non-Saccharomyces yeasts have gained considerable attention as a novel strategy to enhance the aroma diversity of alcoholic beverages. This study explores the effect of sequential fermentations involving Lachancea thermotolerans and Torulaspora delbrueckii on the aroma profile of apple spirits. Additionally, the influence of time, temperature, and alcohol content on the volatile composition during the maturation of distillates was described. The results revealed that distillates obtained from mixed cultures exhibited improved aroma complexity, primarily due to increased ester production. Torulaspora delbrueckii positively influenced the synthesis of 2-phenethyl acetate, diethyl succinate, and hexyl acetate. Lachancea thermotolerans promoted the formation of ethyl lactate, ethyl myristate, and ethyl phenylacetate while reducing the concentration of higher alcohols. During maturation, changes in aroma constituents were observed. In general, the concentration of the investigated volatile compounds tends to decrease during maturation, with this trend being strongly related to the alcohol content of the distillates. Temperature did not affect the variations of methanol, acetaldehyde, 1-propanol, 2-butanol, 2-methyl-1-butanol, cis-2-hexen-1-ol, and diethyl succinate. Regarding esters, increases were observed in the concentration of ethyl octanoate, ethyl myristate, and, under certain circumstances, ethyl acetate and isoamyl acetate. No correlation was found between changes in acetaldehyde and the conditions tested. [ABSTRACT FROM AUTHOR]

Two novel synthetic routes to 4‐(N‐Boc‐N‐methylaminomethyl)benzaldehyde, an important pharmaceutical starting material, were developed using terephthaloyl chloride and terephthalaldehyde. In the first approach, terephthaloyl chloride was converted to an ester amide. The treatment of the ester amide with LiAlH4 followed by protection of the resulting amine with tert‐butoxycarbonyl anhydride yielded the corresponding benzyl alcohol. The benzyl alcohol was oxidized to the aldehyde completing the first‐generation synthesis. The second approach utilized a one‐step protocol mono‐selective reductive amination of terephthalaldehyde with N‐Boc‐methylamine using chlorodimethylsilane. Both methods were scalable to 50 mmol and provided the desired aldehyde in a synthetically useful yield, demonstrating their practicality. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Comprehensive Summary The present work prepared a copper N‐heterocyclic carbene complex that could be used in catalyzing the homogeneous hydrogenation of carboxylic acid with ammonia borane (hydrogen source) to synthesize primary alcohols. Various aromatic and aliphatic carboxylic acids with diverse functional groups were transformed to respective alcohols in moderate to high yields. The process can be easily scaled up (TON up to 14545) and exhibits a high compatibility with different sensitive functional groups, including fluorine, chlorine, bromine, iodine, hydroxyl, cyano and nitro groups. IMesCuCl/NH3·BH3 combination can selectively reduce aromatic and aliphatic esters. Mechanistic studies indicate that Cu‐H species produced in situ are the active intermediates. [ABSTRACT FROM AUTHOR]

Non‐directed regioselective activation of bis(boronic esters), followed by functionalization, is reported. A bulky activator is shown to selectively activate the less hindered boronic ester enabling it to undergo stereospecific cross‐coupling to a variety of electrophiles. This steric‐based regioselectivity provides a simple and efficient method to prepare highly functionalized, enantiomerically enriched products starting from simple alkenes. [ABSTRACT FROM AUTHOR]

Global production of synthetic polyamides (PA), or nylons, is increasing while recycling rates are currently below 5% contributing to the global plastics crisis. Enzymatic depolymerization is a powerful strategy to overcome the drawbacks of mechanical and chemical recycling and has the potential to increase PA recycling rates. However, enzymatic depolymerization of PA is currently limited to a small group of nylonases (NylC) that exhibit low activities making them unsuitable for efficient enzymatic recycling. In this study, we extend the diversity of nylonases, namely NylC1, NylC2, and NylC3 by library screenings and in silico analysis. Three novel nylonases were identified that showed varying sequence identities ranging from 84 to 32% compared to the previously characterized NylCp2 from Paenarthrobacter ureafaciens. Activity of these nylonase candidates towards cyclic PA-oligomers was confirmed via the detection of soluble degradation products. These nylonases were also active on synthesized poly(ester amides) (PEA), and this activity was synergistically increased by combination with the leaf and branch compost cutinase LCC resulting in the hydrolysis of approximately 1% of the total polymer. Overall, our discoveries greatly increase the sequence space of NylC enzymes for future enzyme engineering strategies to boost their activities, and they show the potential of PEA for tuning the biodegradability of performance polymers. Thereby, this study leads the path for developing efficient enzymatic PA and PEA depolymerization processes, revealing significant insights into combining the contrary parameters of performance and biodegradability of polymers. [ABSTRACT FROM AUTHOR]

Cellulose nanomaterials are derived from the most abundant biopolymer on earth, and are gaining importance in the shift from oil-based materials to sustainable alternatives. To facilitate this, sustainable methods to modify these renewable nanostructured materials must be explored, as surface modifications are prerequisite for many nanocellulose applications. Here, we present a solvent-free method for the surface modification of cellulose nanocrystals, encompassing mechanochemistry to convert uncharged or charged CNCs to tosylated CNCs, and for the subsequent versatile nucleophilic substitution with amines and esters. Systematic screening of the reaction parameters revealed key variables - milling time, base type and amount, for tosylation to take place during 60 minutes of ball-milling without major changes to CNC morphology and crystallinity. Both step-wise and one-step in situ nucleophilic substitution of the tosyl CNCs was successful with amine and ester modification. Our results demonstrate how fine-tuning the parameters of solvent-free methods can lead to fast and environmentally benign reactions on cellulose nanomaterials while retaining their structure on the nanoscale. [ABSTRACT FROM AUTHOR]

The myriad nickel-catalyzed cross-coupling reactions rely on the formation of an organonickel intermediate, but limitations in forming monoalkylnickel species have limited options for C(sp3) cross-coupling. The formation of monoalkylnickel(II) species from abundant carboxylic acid esters would be valuable, but carboxylic acid derivatives are primarily decarboxylated to form alkyl radicals that lack the correct reactivity. In this work, we disclose a facile oxidative addition and decarbonylation sequence that forms monoalkylnickel(II) intermediates through a nonradical process. The key ligand, bis(4-methylpyrazole)pyridine, accelerates decarbonylation, stabilizes the alkylnickel(II) intermediate, and destabilizes off-cycle nickel(0) carbonyl species. The utility of this new reactivity in C(sp3)-C(sp3) bond formation is demonstrated in a reaction that is challenging by purely radical methods—the selective cross-coupling of primary carboxylic acid esters with primary alkyl iodides. [ABSTRACT FROM AUTHOR]

The construction and application of smart hydrogels often involve balancing the conflicting relationship between the stability and dynamics. Imine bond, as a type of dynamic chemical bonding, is commonly used in the construction of diverse smart hydrogels since it can effectively achieve the response to some external stimuli. However, its poor thermodynamic stability often leads to the limited crosslinking density and easy degradation of hydrogels in water and biofluids. To address this critical issue, a series of model smart hydrogels is prepared with highly water stability and stimuli responsiveness via the iminoboronate gelation of aminoglycosides and 8‐arm PEG terminated with 2‐acetylphenylboronic acid pinacol ester [(pin)‐APBA]. Note that the presence of pinacol esters, as electron‐donating agents and hydrophobic couplers with large steric hindrance, can keep the five‐membered ring of iminoboronate intact and protect the nitrogen‐boron (N─B) coordination bond from water molecules, offering the water resistance feature of the hydrogels. And the rapid responsiveness of the gels to stimuli (e.g., acid, H2O2 and unhindered amines) further confirmed that their dynamic nature, allowing the on‐demand release of aminoglycosides with satisfactory antibacterial effect. This iminoboronate chemistry‐based strategy can offer new opportunities toward stable and smart hydrogels with various applications in many fields. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Key Scientists Boronate esters are highly valued in synthetic and pharmaceutical industries for their versatility in creating C—C and C—X bonds. They also find applications as catalysts in chemical transformations as well as stimuli‐responsive materials in materials science. Some alkyl boronates themselves also show promising applications in medicinal chemistry. In the past few decades, chemists have been devoted to developing new methods or new starting materials for synthesizing boronate esters. Carboxylic acids and their derivatives are privileged chemical entities due to their readily availability or natural abundance, structural diversity, and chemical stability. Hence, the transformation of carboxylic acid and their derivatives to alkyl/aryl boronate esters has seen its fast development in the past decade. This review summarized the state‐to‐art development of decarboxylative and decarbonylative borylation of carboxylic acids and their derivatives to aryl and alkyl boronate esters.The decarboxylative and decarbonylative borylation of carboxylic acids and their derivatives started only in the past decade. In 2016, the decarbonylative borylation of carboxylic esters and amides was reported by Zhuangzhi Shi and Magnus Reuping's groups. Then, in 2017, studies on the decarboxylative borylation of redox‐active esters such as NHPI esters started to receive increasing attention by Aggarwal, Baran, Fu, Glorius, and Li's groups. From 2018 to 2023, large numbers of studies on the decarboxylative and decarbonylative borylation of carboxylic acids and their derivatives using transition‐metal‐catalyst, organo‐catalyst, or under photochemical or electrochemical conditions emerged. Due to space limitations, only pictures of scientists who have contributed more than two works in this area are shown herein. [ABSTRACT FROM AUTHOR]

A metal-free and sustainable visible-light-mediated method for the preparation of organic nitrate esters has been developed through the aerobic nitrooxylation reaction of α-diazoesters and cyclic ethers with t-BuONO in the presence of dioxygen. This protocol provides an efficient approach to access nitrate esters with the advantages of clean energy, broad substrate scope, green oxidants, operational simplicity, and mild conditions. [ABSTRACT FROM AUTHOR]