Pd(0)-Catalyzed Asymmetric Intramolecular Grignard-Type Reaction of Vinyl Iodide-Carbonyl

The insertion of carbonyl into C(sp2)-Pd(II) σ-bond (Grignard-type addition) was not established until the 1990s. While this elemental reaction has been well explored since then, its application in Pd(0) asymmetric catalysis remain elusive. Herein, we report the Pd(0)-catalyzed asymmetric intramolecular Grignard-type reaction of vinyl iodide-carbonyl in the presence of HCO2H additive, affording cyclic allylic alcohol with good to excellent enantioselectivity and diastereoselectivity. Mechanistic studies suggested that besides serving as an efficient reductant, HCO2H is also capable of facilitating protonation of the involved secondary alkoxyl-Pd(II), thus completely suppressing the β-H elimination. Moreover, no KIE was found in the competing reaction between vinyl iodide-aldehyde and 1-deuterated one, demonstrating the facile step of aldehyde insertion.

Uncovering the roles of Mycobacterium tuberculosis melH in redox and bioenergetic homeostasis: implications for antitubercular therapy

Mycobacterium tuberculosis (Mtb), the pathogenic bacterium that causes tuberculosis, has evolved sophisticated defense mechanisms to counteract the cytotoxicity of reactive oxygen species (ROS) generated within host macrophages during infection. The melH gene in Mtb and Mycobacterium marinum (Mm) plays a crucial role in defense mechanisms against ROS generated during infection. We demonstrate that melH encodes an epoxide hydrolase and contributes to ROS detoxification. Deletion of melH in Mm resulted in a mutant with increased sensitivity to oxidative stress, increased accumulation of aldehyde species, and decreased production of mycothiol and ergothioneine. This heightened vulnerability is attributed to the increased expression of whiB3, a universal stress sensor. The absence of melH also resulted in reduced intracellular levels of NAD+, NADH, and ATP. Bacterial growth was impaired, even in the absence of external stressors, and the impairment was carbon source dependent. Initial MelH substrate specificity studies demonstrate a preference for epoxides with a single aromatic substituent. Taken together, these results highlight the role of melH in mycobacterial bioenergetic metabolism and provide new insights into the complex interplay between redox homeostasis and generation of reactive aldehyde species in mycobacteria.

IMPORTANCE

This study unveils the pivotal role played by the melH gene in Mycobacterium tuberculosis and in Mycobacterium marinum in combatting the detrimental impact of oxidative conditions during infection. This investigation revealed notable alterations in the level of cytokinin-associated aldehyde, para-hydroxybenzaldehyde, as well as the redox buffer ergothioneine, upon deletion of melH. Moreover, changes in crucial cofactors responsible for electron transfer highlighted melH's crucial function in maintaining a delicate equilibrium of redox and bioenergetic processes. MelH prefers epoxide small substrates with a phenyl substituted substrate. These findings collectively emphasize the potential of melH as an attractive target for the development of novel antitubercular therapies that sensitize mycobacteria to host stress, offering new avenues for combating tuberculosis.

Identification of two critical amino acid residues in short-chain aldehyde-responsive odorant receptors

Mammalian odorant receptors (ORs) are crucial for detecting a broad spectrum of odorants, yet their functional expression poses a significant challenge, often requiring Receptor-transporting proteins (RTPs). This study examines mouse Olfr733 and Olfr732, which, despite high homology, show different functional expression profiles in heterologous cell systems. Our research aimed to identify key amino acids impacting Olfr733's functional expression. We discovered that G112FBW3.40 and L148PBW4.49 (Ballesteros-Weinstein numbering in superscript) substitutions in Olfr732 markedly enhance its RTP-independent expression and ligand responsiveness, mirroring Olfr733. These substitutions, particularly Phe112 and Leu148, are crucial for aldehyde recognition and membrane localization in Olfr733, respectively. While Olfr732-type ORs are conserved across species, Olfr733-types, unique to specific rodents, appear to have evolved from Olfr732, with Pro148 enhancing membrane expression and aldehyde sensitivity. Mouse ORs with ProBW4.49 tend to exhibit improved membrane expression compared to their paralogs, especially when co-expressed with RTP1S. This study concludes that the Pro residue in the fourth transmembrane domain significantly contributes to the structural stability of certain olfactory receptors, highlighting the intricate molecular mechanisms underlying OR functionality and evolution.

Green and sustainable approaches for the Friedel-Crafts reaction between aldehydes and indoles

The synthesis of indoles and their derivatives, more specifically bis(indolyl)methanes (BIMs), has been an area of great interest in organic chemistry, since these compounds exhibit a range of interesting biological and pharmacological properties. BIMs are naturally found in cruciferous vegetables and have been shown to be effective antifungal, antibacterial, anti-inflammatory, and even anticancer agents. Traditionally, the synthesis of BIMs has been achieved upon the acidic condensation of an aldehyde with indole, utilizing a variety of protic or Lewis acids. However, due to the increased environmental awareness of our society, the focus has shifted towards the development of greener synthetic technologies, like photocatalysis, organocatalysis, the use of nanocatalysts, microwave irradiation, ball milling, continuous flow, and many more. Thus, in this review, we summarize the medicinal properties of BIMs and the developed BIM synthetic protocols, utilizing the reaction between aldehydes with indoles, while focusing on the more environmentally friendly methods developed over the years.

Pinacol Cross-Coupling Promoted by an Aluminyl Anion

A simple sequential addition protocol for the reductive coupling of ketones and aldehydes by a potassium aluminyl grants access to unsymmetrical pinacolate derivatives. Isolation of an aluminium ketyl complex presents evidence for the accessibility of radical species. Product release from the aluminium centre was achieved using an iodosilane, forming the disilylated 1,2-diol and a neutral aluminium iodide, thereby demonstrating the steps required to generate a closed synthetic cycle for pinacol (cross) coupling at an aluminyl anion.

An Overview of Julia-lythgoe Olefination

Julia-Lythgoe olefination (or simply Julia olefination) is an olefination process between phenyl sulfones and aldehydes (or ketones) to give alkenes after alcohol functionalization and reductive elimination using sodium amalgam or SmI2. It is mainly used to synthesize E-alkenes and is a key step in numerous total syntheses of many natural products. This review exclusively deals with the Julia-Lythgoe olefination and concentrates mainly on the applications of this reaction in natural product synthesis covering literature up to 2021.

Pathologically relevant aldoses and environmental aldehydes cause cilium disassembly via formyl group-mediated mechanisms

Carbohydrate metabolism disorders (CMDs), such as diabetes, galactosemia, and mannosidosis, cause ciliopathy-like multiorgan defects. However, the mechanistic link of cilia to CMD complications is still poorly understood. Herein, we describe a significant cilium disassembly upon treatment of cells with pathologically relevant aldoses rather than the corresponding sugar alcohols. Moreover, environmental aldehydes are able to trigger cilium disassembly by the steric hindrance effect of their formyl groups. Mechanistic studies reveal that aldehydes stimulate extracellular calcium influx across the plasma membrane, which subsequently activates the calmodulin-Aurora A-histone deacetylase 6 pathway to deacetylate axonemal microtubules and triggers cilium disassembly. In vivo experiments further show that Hdac6 knockout mice are resistant to aldehyde-induced disassembly of tracheal cilia and sperm flagella. These findings reveal a previously unrecognized role for formyl group-mediated cilium disassembly in the complications of CMDs.

Development of a Sensitive and Selective Method for the Determination of some Selected Aldehydes Based on Fluorescence Quenching

Phenanthrene fluorescence quenching in anionic micellar system of sodium dodecyl sulphate (SDS) was explored for the development of a sensitive and selective method for a group of selected aldehydes (2,6-dichlorobenzaldehyde, 4-(dimethylamino)benzaldehyde, 4-aminobenzaldehyde, 4-nitrobenzaldehyde, 2-chlorobenzaldehyde, benzaldehyde and 2-methoxybenzaldehyde). Experiments were performed in 0.02 mol L- 1 SDS. All the studied aldehydes quenched the fluorescence intensity of the probe (phenanthrene). Stern-Volmer equation was useful in explaining the phenanthrene quenching by the studied aldehydes. Stern-Volmer constants ([Formula: see text]) were obtained as a result of using the Stern-Volmer equation that gives the information in respect of sensitivity of the method for the studied aldehydes. Greater the [Formula: see text] higher will be the sensitivity and vice versa. [Formula: see text], detection limit (DL) and quantification limit (QL) were observed in the order 2,6-dichlorobenzaldehyde > 4-dimethylaminobenzaldehyde > 4-aminobenzaldehyde > 4-nitrobenzaldehyde > 2-chlorobenzaldehyde > benzaldehyde > 2-methoxybenzaldehyde. Phenanthrene fluorescence quenching by the studied aldehydes is useful for their determination in environmental samples.

Modification of the Human Amniotic Membrane Using Different Cross-Linking Agents as a Promising Tool for Regenerative Medicine

Human amniotic membranes (hAMs) obtained during cesarean sections have proven to be clinically useful as an interesting biomaterial in a wide range of tissue engineering applications such as ocular surface reconstruction, burn treatments, chronic wounds, or bedsore ulcers. It presents antimicrobial properties, promotes epithelization, reduces inflammation and angiogenesis, contains growth factors, and constitutes the reservoir of stem cells. However, variability in hAM stiffness and its fast degradation offers an explanation for the poor clinical applications and reproducibility. In addition, the preparatory method of hAM for clinical use can affect its mechanical properties, and these differences can influence its application. As a directly applied biomaterial, the hAM should be available in a ready-to-use manner in clinical settings. In the present study, we performed an analysis to improve the mechanical properties of hAM by the addition of various reagents used as protein cross-linkers: EDC/NHS, PEG-dialdehyde, PEG-NHS, dialdehyde starch, and squaric acid. The effect of hAM modification using different cross-linking agents was determined via infrared spectroscopy, thermal analyses, mechanical properties analyses, enzymatic degradation, and cytotoxicity tests. The use of PEG-dialdehyde, PEG-NHS, dialdehyde starch, and squaric acid increases the mechanical strength and elongation at the breaking point of hAM, while the addition of EDC/NHS results in material stiffening and shrinkage. Also, the thermal stability and degradation resistance were evaluated, demonstrating higher values after cross-linking. Overall, these results suggest that modification of human amniotic membrane by various reagents used as protein cross-linkers may make it easier to use hAM in clinical applications, and the presented study is a step forward in the standardization of the hAM preparation method.

Straightforward Synthesis of Halopyridine Aldehydes via Diaminomethylation

A novel two-step method for formylation of fluoropyridines with silylformamidine Me3 SiC(=NMe)NMe2 (1) under catalyst-free conditions was developed. A series of all possible 18 fluoropyridines featuring one to four fluorine atoms were subjected to the reaction with 1 existing in equilibrium with its carbenic form Me2 NC(:)N(Me)SiMe3 (1'). Among them, 12 fluoropyridines were shown to react via C-H insertion. The reaction proceeded either at β- or γ-positions affording the corresponding aminals. The more fluorine atoms in pyridines, the easier the reaction proceeded. We also hypothesized that the pyridines in which the fluorine was substituted by other halogens would react in a similar manner. To test the hypothesis, a set of 3,5-disubstituted pyridines with various combination of halogen atoms was prepared. 3,5-Difluoropyridine was taken as a compound for comparison. All the pyridines in the series also reacted likewise. In most cases, hydrolysis of the aminals afforded the corresponding aldehydes. As DFT calculations indicate, the reaction mechanism includes deprotonation of pyridine by 1' as a strong base and the following rearrangement of the formed tight ionic pair to the final product. An alternative reaction pathway involving addition of 1' to the pyridine carbon with the following hydrogen transfer via a three-membered transition state structure required much higher activation energy.

Aldehyde accumulation in Mycobacterium tuberculosis with defective proteasomal degradation results in copper sensitivity

Mycobacterium tuberculosis is a major human pathogen and the causative agent of tuberculosis disease. M. tuberculosis is able to persist in the face of host-derived antimicrobial molecules nitric oxide (NO) and copper (Cu). However, M. tuberculosis with defective proteasome activity is highly sensitive to NO and Cu, making the proteasome an attractive target for drug development. Previous work linked NO susceptibility with the accumulation of para-hydroxybenzaldehyde (pHBA) in M. tuberculosis mutants with defective proteasomal degradation. In this study, we found that pHBA accumulation was also responsible for Cu sensitivity in these strains. We showed that exogenous addition of pHBA to wild-type M. tuberculosis cultures sensitized bacteria to Cu to a degree similar to that of a proteasomal degradation mutant. We determined that pHBA reduced the production and function of critical Cu resistance proteins of the regulated in copper repressor (RicR) regulon. Furthermore, we extended these Cu-sensitizing effects to an aldehyde that M. tuberculosis may face within the macrophage. Collectively, this study is the first to mechanistically propose how aldehydes can render M. tuberculosis susceptible to an existing host defense and could support a broader role for aldehydes in controlling M. tuberculosis infections. IMPORTANCE M. tuberculosis is a leading cause of death by a single infectious agent, causing 1.5 million deaths annually. An effective vaccine for M. tuberculosis infections is currently lacking, and prior infection does not typically provide robust immunity to subsequent infections. Nonetheless, immunocompetent humans can control M. tuberculosis infections for decades. For these reasons, a clear understanding of how mammalian immunity inhibits mycobacterial growth is warranted. In this study, we show aldehydes can increase M. tuberculosis susceptibility to copper, an established antibacterial metal used by immune cells to control M. tuberculosis and other microbes. Given that activated macrophages produce increased amounts of aldehydes during infection, we propose host-derived aldehydes may help control bacterial infections, making aldehydes a previously unappreciated antimicrobial defense.

Impact of common ALDH2 inactivating mutation and alcohol consumption on Alzheimer's disease

Aldehyde dehydrogenase 2 (ALDH2) is an enzyme found in the mitochondrial matrix that plays a central role in alcohol and aldehyde metabolism. A common ALDH2 polymorphism in East Asians descent (called ALDH2*2 or E504K missense variant, SNP ID: rs671), present in approximately 8% of the world's population, has been associated with a variety of diseases. Recent meta-analyses support the relationship between this ALDH2 polymorphism and Alzheimer's disease (AD). And AD-like pathology observed in ALDH2-/- null mice and ALDH2*2 overexpressing transgenic mice indicate that ALDH2 deficiency plays an important role in the pathogenesis of AD. Recently, the worldwide increase in alcohol consumption has drawn attention to the relationship between heavy alcohol consumption and AD. Of potential clinical significance, chronic administration of alcohol in ALDH2*2/*2 knock-in mice exacerbates the pathogenesis of AD-like symptoms. Therefore, ALDH2 polymorphism and alcohol consumption likely play an important role in the onset and progression of AD. Here, we review the data on the relationship between ALDH2 polymorphism, alcohol, and AD, and summarize what is currently known about the role of the common ALDH2 inactivating mutation, ALDH2*2, and alcohol in the onset and progression of AD.

Efficient Synthesis of 2-Ethylhexanoic Acid via N-Hydroxyphthalimide Catalyzed Oxidation of 2-Ethylhexanal with Oxygen

An efficient method for the synthesis of 2-ethylhexanoic acid has been reported. The method involves the 2-ethylhexanal oxidation using oxygen or air in the presence of N-hydroxyphthalimide in isobutanol as a solvent under mild conditions. A high selectivity of >99% for 2-ethylhexanoic acid was achieved. The influence of catalyst amount, solvent type and quantity, temperature, and reaction time on the product composition was studied. The developed method is in line with the global trends aimed at developing green oxidation processes as well as having potential for implementation in industry due to its high selectivity, cost-effective oxidizing agent, and mild reaction conditions. The use of isobutanol as a solvent is of crucial importance providing an opportunity for potential producers of 2-EHAL from butanal to employ the less valuable alcohol.

Effects of Stigmasterol on 3-Chloropropane-1,2-diol Fatty Acid Esters and Aldehydes Formation in Heated Soybean Oil

In this study, we investigated the inhibitory effects of three soybean isoflavones and two soybean phytosterols on the formation of 3-chloropropane-1,2-diol fatty acid esters (3-MCPDE) and aldehydes in heated soybean oil model. 0.4 mM of genistin, genistein, daidzein, stigmasterol, and β-sitosterol significantly reduced 3-MCPDE formation by 25.7, 51.4, 21.4, 61.6, and 55.7%, and total aldehydes formation by 42.03, 43.94, 28.36, 54.74, and 39.23%, respectively. Further study showed that stigmasterol reduced the content of glycidyl esters (GEs) and glycidol, two key intermediates of 3-MCPDE, and prevented fatty acids degradation in the oils. Moreover, the effects of continuous frying time on the content of stigmasterol and the migration of stigmasterol were evaluated in the fried dough sticks model system. The content of stigmasterol in soybean oil was found to be significantly decreased with prolonged heating time. The concentrations of stigmasterol in fried dough sticks and the migration rates of stigmasterol from soybean oil to fried dough sticks decreased with repeated frying sessions. In addition, stigmasterol undergoes oxidative changes during heat treatment, and the oxidation products including 5,6α-epoxystigmasterol, 5,6β-epoxystigmasterol, 7α-hydroxystigmasterol, 7β-hydroxystigmasterol, stigmasterlol-3β,5α,6β-triol, and 7-ketostigmasterol were identified in the frying oils but not in the fried dough sticks. Overall, stigmasterol could be added to soybean oil to reduce 3-MCPDE and aldehydes formation, and reacting with GEs/glycidol and protection of lipid acids from oxidation may be the mechanism of action of stigmasterol.

Direct Alkylative Amination Using 1-Allylsilatrane

Homoallylic amines prepared via addition of allylsilanes often require preformed imine substrates, metal catalysts, fluoride activators, or use of protected amines. In this metal-free, air- and water-tolerant procedure, aromatic aldehyde and aniline substrates undergo direct alkylative amination using easily accessible 1-allylsilatrane.

Cu-Based Bimetallic Catalysts for Electrocatalytic Oxidative Dehydrogenation of Furfural with Practical Rates

Electrocatalytic oxidative dehydrogenation (EOD) of aldehydes enables ultra-low voltage, bipolar H2 production with co-generation of carboxylic acid. Herein, we reported a simple galvanic replacement method to prepare CuM (M = Pt, Pd, Au, and Ag) bimetallic catalysts to improve the EOD of furfural to reach industrially relevant current densities. The redox potential difference between Cu/Cu2+ and a noble metal M/My+ can incorporate the noble metal on the Cu surface and enlarge its surface area. Particularly, dispersing Pt in Cu (CuPt) achieved a record-high current density of 498 mA cm-2 for bipolar H2 production at a low cell voltage of 0.6 V and a Faradaic efficiency of >80% to H2. Future research is needed to deeply understand the synergistic effects of Cu-M toward EOD of furfural, and improve the Cu-M catalyst stability, thus offering great opportunities for future distributed manufacturing of green hydrogen and carbon chemicals with practical rates and low-carbon footprints.

Enzymatic reactions towards aldehydes: An overview

Many aldehydes are volatile compounds with distinct and characteristic olfactory properties. The aldehydic functional group is reactive and, as such, an invaluable chemical multi-tool to make all sorts of products. Owing to the reactivity, the selective synthesis of aldehydic is a challenging task. Nature has evolved a number of enzymatic reactions to produce aldehydes, and this review provides an overview of aldehyde-forming reactions in biological systems and beyond. Whereas some of these biotransformations are still in their infancy in terms of synthetic applicability, others are developed to an extent that allows their implementation as industrial biocatalysts.

Volatile Short-Chain Aliphatic Aldehydes Act as Taste Modulators through the Orally Expressed Calcium-Sensing Receptor CaSR

Aldehydes are natural volatile aroma compounds generated by the Maillard reaction of sugars and amino acids in food and affect the flavor of food. They have been reported to exert taste-modifying effects, such as increases in taste intensity at concentrations below the odor detection threshold. The present study examined the taste-enhancing effects of short-chain aliphatic aldehydes, such as isovaleraldehyde (IVAH) and 2-methylbutyraldehyde, thus attempting to identify the taste receptors involved. The results obtained revealed that IVAH enhanced the taste intensity of taste solutions even under the condition of olfactory deprivation by a noseclip. Furthermore, IVAH activated the calcium-sensing receptor CaSR in vitro. Receptor assays on aldehyde analogues showed that C3-C6 aliphatic aldehydes and methional, a C4 sulfur aldehyde, activated CaSR. These aldehydes functioned as a positive allosteric modulator for CaSR. The relationship between the activation of CaSR and taste-modifying effects was investigated by a sensory evaluation. Taste-modifying effects were found to be dependent on the activation state of CaSR. Collectively, these results suggest that short-chain aliphatic aldehydes function as taste modulators that modify sensations by activating orally expressed CaSR. We propose that volatile aroma aldehydes may also partially contribute to the taste-modifying effect via the same molecular mechanism as kokumi substances.

Alkane production from fatty alcohols by the combined reactions catalyzed by an alcohol dehydrogenase and an aldehyde-deformylating oxygenase

PsADH, an alcohol dehydrogenase originating in Pantoea sp. was characterized and found to convert a broad variety of fatty alcohols into their corresponding aldehydes, the substrates of alkane biosynthesis. By coupling PsADH with NpAD, a cyanobacterial aldehyde-deformylating oxygenase, and by optimizing the conditions of the enzyme-catalyzed reactions, we achieved a 52% conversion of 1-tetradecanol to tridecane. We further applied this system to generate alkanes ranging from C5-17. These alkanes can be used as biofuels, suggesting that introducing a suitable alcohol dehydrogenase is an effective strategy to utilize fatty alcohols for alkane production.

A Precise qNMR Method for the Rapid Quantification of Lot-to-Lot Variations in Multiple Quality Attributes of Pentosan Polysulfate Sodium

Pentosan polysulfate sodium (PPS) is an orphan drug with anticoagulant activity. PPS is prepared from the chemical processing of xylan extracted from beechwood tree to yield a mixture of 4-6 kDa polysaccharides. The chain is mainly composed of sulfated xylose (Xyl) with branched 4-O-methyl-glucuronate (MGA). During generic drug development, the quality attributes (QAs) including monosaccharide composition, modification, and length need to be comparable to those found in the reference list drug (RLD). However, the range of QA variation of the RLD PPS has not been well characterized. Here, multiple PPS RLD lots were studied using quantitative NMR (qNMR) and diffusion ordered spectroscopy (DOSY) to quantitate the components in the mixture and to probe both inter- and intra-lot precision variability. The DOSY precision assessed using coefficient of variation (CV) was 6%, comparable to PPS inter-lot CV of 5%. The QAs obtained from 1D qNMR were highly precise with a precision CV < 1%. The inter-lot MGA content was 4.8 ± 0.1%, indicating a very consistent botanical raw material source. Other process-related chemical modification including aldehyde at 0.51 ± 0.04%, acetylation at 3.3 ± 0.2% and pyridine at 2.08 ± 0.06%, varied more than MGA content. The study demonstrated that 1D qNMR is a quick and precise method to reveal ranges of variation in multiple attributes of RLD PPS which can be used to assess equivalency with generic formulations. Interestingly, the synthetic process appeared to introduce more variations to the PPS product than the botanical source of the material.

Increased alcohol dehydrogenase 1 activity promotes longevity

Several molecules can extend healthspan and lifespan across organisms. However, most are upstream signaling hubs or transcription factors orchestrating complex anti-aging programs. Therefore, these molecules point to but do not reveal the fundamental mechanisms driving longevity. Instead, downstream effectors that are necessary and sufficient to promote longevity across conditions or organisms may reveal the fundamental anti-aging drivers. Toward this goal, we searched for effectors acting downstream of the transcription factor EB (TFEB), known as HLH-30 in C. elegans, because TFEB/HLH-30 is necessary across anti-aging interventions and its overexpression is sufficient to extend C. elegans lifespan and reduce biomarkers of aging in mammals including humans. As a result, we present an alcohol-dehydrogenase-mediated anti-aging response (AMAR) that is essential for C. elegans longevity driven by HLH-30 overexpression, caloric restriction, mTOR inhibition, and insulin-signaling deficiency. The sole overexpression of ADH-1 is sufficient to activate AMAR, which extends healthspan and lifespan by reducing the levels of glycerol-an age-associated and aging-promoting alcohol. Adh1 overexpression is also sufficient to promote longevity in yeast, and adh-1 orthologs are induced in calorically restricted mice and humans, hinting at ADH-1 acting as an anti-aging effector across phyla.

Synthesis of 1,1-Disubstituted Allenylic Silyl Ethers Through Iron-Catalyzed Regioselective C(sp2)─H Functionalization of Allenes

We report a synthesis of allenylic silyl ethers through iron-catalyzed functionalization of the C(sp2)─H bonds of monosubstituted alkylallenes. In the presence of a cyclopentadienyliron dicarbonyl based catalyst and triisopropylsilyl triflate as a silylation agent, a variety of aryl aldehydes were suitable coupling partners in this transformation, furnishing a collection of 1,1-disubstituted allenylic triisopropylsilyl ethers as products in moderate to excellent yields as a single regioisomer. Lithium bistriflimide was identified as a critical additive in this transformation. The optimized protocol was scalable, and the products were amenable to further transformation to give a number of unsaturated, polyfunctional derivatives.

Effect of Bed Bug (Hemiptera: Cimicidae) Aldehydes on Efficacy of Fungal Biopesticides

The use of the entomopathogenic fungus Beauveria bassiana (Bals. - Criv.) Vuill. (Hypocreales: Cordycipitaceae) has been recently incorporated in the management of bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae). Bed bugs produce a set of aldehydes that are known to affect the growth of some fungi. Considering that bed bugs or their exuviae release these aldehydes, it was suspected that the bed bugs' aggregation sites would contain an increased level of the bed bug aldehydes. The current study examined if elevated levels of the bed bug aldehydes in the microhabitats would impact the efficacy of B. bassiana. Following a brief exposure to the residues of commercial products containing B. bassiana, the treated bed bugs were kept in a vial with or without a natural or artificial blend of bed bug aldehydes (i.e., exuviae or synthetic compounds). For a B. bassiana product that is not currently registered for bed bugs control, the presence of aldehydes significantly reduced 15-d mortality (61-62%) compared to the no aldehydes control (97.7%). However, when tested with a B. bassiana formulation designed for bed bug control, the aldehydes only caused delayed mortality for the treated bed bugs. When tested in culture, the growth rate of B. bassiana on a medium was significantly reduced when the bed bug aldehydes were provided in the headspace. Implications on practical bed bug management using fungal biopesticides are discussed.

Electrocatalytic Aldehyde Oxidation by a Tungsten Dependent Aldehyde Oxidoreductase from Aromatoleum Aromaticum

In contrast to their molybdenum dependent relatives, tungsten enzymes operate at significantly lower redox potentials, and in some cases they can carry out reversible redox transformations of their substrates and products. Still, the electrochemical properties of W enzymes have received much less attention than their Mo relatives. Herein we analyse the tungsten enzyme aldehyde oxidoreductase (AOR) from the mesophilic bacterium Aromatoleum aromaticum which has been immobilised on a glassy carbon working electrode. This generates a functional system that electrochemically oxidises a wide variety of aromatic and aliphatic aldehydes in the presence of the electron transfer mediators benzyl viologen, methylene blue or dichlorophenol indophenol. Simulation of the cyclic voltammetry has enabled a thorough kinetic analysis of the system, which reveals that methylene blue acts as a two-electron acceptor. In contrast, the other two mediators act as single electron oxidants. The different electrochemical driving forces imparted by these mediators also lead to significantly different outer sphere electron transfer rates with AOR. This work shows that electrocatalytic aldehyde oxidation can be achieved at a low applied electrochemical potential leading to an extremely energy efficient catalytic process.

Novel aldo-keto reductase AKR2E9 regulates aldehyde content in the midgut and antennae of the silkworm (Bombyx mori)

We studied the effects of green leaf volatiles (including reactive aldehydes) emitted by plants on insects that feed on these plants. The silkworm (Bombyx mori) is a model lepidopteran that eats mulberry leaves. Defense-related enzymes in silkworms can be targeted for developing new pest control methods. The aldo-keto reductase (AKR) superfamily catalyzes aldehyde reduction by converting a carbonyl group into an alcohol group. Here, we characterized a novel silkworm AKR, designated as AKR2E9. Recombinant AKR2E9 was overexpressed in Escherichia coli. The recombinant protein was used, along with nicotinamide adenine dinucleotide phosphate as a coenzyme, to reduce aldehydes present in mulberry (Morus alba) leaves. The catalytic efficiency of AKR2E9 toward various aldehyde substrates and its inhibitor sensitivity was lower than those of AKR2E8. High expression levels of akr2e9 messenger RNA (mRNA) were detected in the midgut and antennae of silkworms. In the antennae of adult silkworms, akr2e9 mRNA was more abundant than akr2e8 mRNA. The catalytic efficiency of AKR2E9 was low because of steric hindrance, due to which its active site is blocked. High expression levels of AKR2E9 in the midgut and antennae suggest that it may regulate the detoxification of toxic aldehydes in silkworms.

Characterization of the aroma compounds in crystal malt

Crystal malt, the most popular type of specialty malt used in beer brewing, plays a vital role in forming complex flavor and color. Nevertheless, crystal malt is only defined based on the malting process, and there is not any standard to evaluate its quality. In the current study, the volatile aroma constituents of commercial crystal malt samples were analyzed with headspace solid-phase microextraction combined with gas chromatography-mass spectrometry, in order to explore the characteristic aroma compounds of crystal malt. The average concentration of volatile aroma compounds in 10 crystal malt samples is 587 µg L^-1 , ranging from 347 to 1265 µg L^-1 . A total of 38 aroma compounds were identified, 47% of which were existed in all the 10 samples. Based on principal component analysis and odor activity value, isobutyraldehyde, 2-methylbutanal, furfural, 2-acetyl-1H-pyrrole, oct-1-en-3-ol, 4-methyl-2-phenyl-2-pentenal, and (2E)-2-isopropyl-5-methyl-2-hexenal could be considered the characteristic aroma compounds of crystal malt. The results of this present study would help to establish a standard to assess the quality traits of crystal malt sample.

Naphthalimide-Based Fluorescent Probe for Profiling of Aldehydes during Oxidation of Unsaturated Lipids

A lipophilic naphthalimide hydrazine fluorescent probe was successfully developed in this study for profiling aldehyde oxidation products. Dodecyl amine was applied to afford lipophilicity of the fluorescent probe for lipids. Investigation of fluorescence properties of the probe and condensation products with typical aldehydes including MDA and hexanal revealed significant enhancement of fluorescence intensity after condensation due to the inhibition of photo-induced electron transfer. MDA and hexanal could be differentiated by the probe through emission of different fluorescence colors (blue, MDA; green, hexanal). Eight major oxidation components including seven aldehydes were detected by the fluorescent probe coupled with high-performance liquid chromatography-mass spectrometry during aerobic oxidation of typical unsaturated lipids. Formation of these aldehyde oxidation products was rationalized through the radical oxidation mechanism. Detection of representative aldehyde products demonstrated the generality in the application of this fluorescent probe for profiling of aldehydes after lipid oxidation.

Dual Hydrazine-Equipped Turn-On Manganese-Based Probes for Magnetic Resonance Imaging of Liver Fibrogenesis

Liver fibrogenesis is accompanied by upregulation of lysyl oxidase enzymes, which catalyze oxidation of lysine ε-amino groups on the extracellular matrix proteins to form the aldehyde containing amino acid allysine (LysAld). Here, we describe the design and synthesis of novel manganese-based MRI probes with high signal amplification for imaging liver fibrogenesis. Rational design of a series of stable hydrazine-equipped manganese MRI probes gives Mn-2CHyd with the highest affinity and turn-on relaxivity (4-fold) upon reaction with LysAld. A dynamic PET-MRI study using [52Mn]Mn-2CHyd showed low liver uptake of the probe in healthy mice. The ability of the probe to detect liver fibrogenesis was then demonstrated in vivo in CCl4-injured mice. This study enables further development and application of manganese-based hydrazine-equipped probes for imaging liver fibrogenesis.

Biological Role of Pazopanib and Sunitinib Aldehyde Derivatives in Drug-Induced Liver Injury

Tyrosine kinase inhibitors pazopanib and sunitinib are both used to treat advanced renal cell carcinoma but expose patients to an increased risk of hepatotoxicity. We have previously identified two aldehyde derivatives for pazopanib and sunitinib (P-CHO and S-CHO, respectively) in liver microsomes. In this study, we aimed to decipher their role in hepatotoxicity by treating HepG2 and HepaRG hepatic cell lines with these derivatives and evaluating cell viability, mitochondrial dysfunction, and oxidative stress accumulation. Additionally, plasma concentrations of P-CHO were assessed in a cohort of patients treated with pazopanib. Results showed that S-CHO slightly decreased the viability of HepG2, but to a lesser extent than sunitinib, and affected the maximal respiratory capacity of the mitochondrial chain. P-CHO decreased viability and ATP production in HepG2. Traces of P-CHO were detected in the plasma of patients treated with pazopanib. Overall, these results showed that P-CHO and S-CHO affect hepatocyte integrity and could be involved in the pazopanib and sunitinib hepatotoxicity.

Lipid Peroxidation Produces a Diverse Mixture of Saturated and Unsaturated Aldehydes in Exhaled Breath That Can Serve as Biomarkers of Lung Cancer-A Review

The peroxidation of unsaturated fatty acids is a widely recognized metabolic process that creates a complex mixture of volatile organic compounds including aldehydes. Elevated levels of reactive oxygen species in cancer cells promote random lipid peroxidation, which leads to a variety of aldehydes. In the case of lung cancer, many of these volatile aldehydes are exhaled and are of interest as potential markers of the disease. Relevant studies reporting aldehydes in the exhaled breath of lung cancer patients were collected for this review by searching the PubMed and SciFinderⁿ databases until 25 May 2022. Information on breath test results, including the biomarker collection, preconcentration, and quantification methods, was extracted and tabulated. Overall, 44 studies were included spanning a period of 34 years. The data show that, as a class, aldehydes are significantly elevated in the breath of lung cancer patients at all stages of the disease relative to healthy control subjects. The type of aldehyde detected and/or deemed to be a biomarker is highly dependent on the method of exhaled breath sampling and analysis. Unsaturated aldehydes, detected primarily when derivatized during preconcentration, are underrepresented as biomarkers given that they are also likely products of lipid peroxidation. Pentanal, hexanal, and heptanal were the most reported aldehydes in studies of exhaled breath from lung cancer patients.

Nickel-Catalyzed Defluorinative Coupling of Aliphatic Aldehydes with Trifluoromethyl Alkenes

A simple procedure is reported for the nickel-catalyzed defluorinative alkylation of unactivated aliphatic aldehydes. The process involves the catalytic reductive union of trifluoromethyl alkenes with aldehydes using a nickel complex of a 6,6'-disubstituted bipyridine ligand with zinc metal as the terminal reductant. The protocol is distinguished by its broad substrate scope, mild conditions, and simple catalytic setup. Reaction outcomes are consistent with the intermediacy of an α-silyloxy(alkyl)nickel intermediate generated by a low-valent nickel catalyst, silyl electrophile, and the aldehyde substrate. Mechanistic findings with cyclopropanecarboxaldehyde provide insights into nature of the reactive intermediates and illustrate fundamental reactivity differences that are governed by subtle changes in ligand and substrate structure.

Oviposition Responses of Female Mediterranean Fruit Flies (Diptera: Tephritidae) to Fruit Volatile Compounds

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the most important pests of fruits worldwide. In the present study, we investigated the ovipositional response of C. capitata females to 37 compounds of fruit volatiles from various chemical groups and the dose response to five of them. Red plastic hollow hemispheres (domes) were used as oviposition substrates in all tests. Twenty of the compounds tested increased female egg laying compared to control substrates that contain no chemicals. With 16 compounds, similar number of eggs was deposited in treated and in control oviposition substrates. One terpene ((±)-linalool) reduced egg laying indicating a deterrent ovipositional effect. Both the esters and aldehydes tested increased the ovipositional responses in C. capitata. Most of the monoterpene hydrocarbons increased oviposition, while oxygenated monoterpenes, sesquiterpenes hydrocarbons, and oxygenated sesquiterpenes had mostly neutral effect. Ethyl hexanoate and R-(+)-limonene increased oviposition in the majority of doses tested. Different doses of (-)-linalool elicited differential female ovipositional responses. In contrast, valencene and citral, regardless of dose did not affect female oviposition. Practical implications of these findings are discussed.

An Automated Aerosol Collection and Extraction System to Characterize Electronic Cigarette Aerosols

Electronic cigarette (e-cigarette) market increased by 122% during 2014–2020 and is expected to continue growing rapidly. Despite their popularity, e-cigarettes are known to emit dangerous levels of toxic compounds (e.g., carbonyls), but a lack of accurate and efficient testing methods is hindering the characterization of e-cigarette aerosols emitted by a wide variety of e-cigarette devices, e-liquids, and use patterns. The aim of this study is to fill this gap by developing an automated E-cigarette Aerosol Collection and Extraction System (E-ACES) consisting of a vaping machine and a collection/extraction system. The puffing system was designed to mimic e-cigarette use patterns (i.e., power output and puff topography) by means of a variable power-supply and a flow control system. The sampling system collects e-cigarette aerosols using a combination of glass wool and a continuously wetted denuder. After the collection stage, the system is automatically washed with absorbing and extracting liquids (e.g., methanol, an acetaldehyde-DNPH solution). The entire system is controlled by a computer. E-ACES performance was evaluated against conventional methods during measurements of nicotine and carbonyl emissions from a tank type e-cigarette. Nicotine levels measured using glass fiber filters and E-ACES were not significantly different: 201.2 ± 6.2 and 212.5 ± 17 μg/puff (p = 0.377), respectively. Differences in formaldehyde and acetaldehyde levels between filter-DNPH cartridges and the E-ACES were 14% (p = 0.057) and 13% (p = 0.380), respectively. The E-ACES showed reproducible nicotine and carbonyl testing results for the selected e-cigarette vaping conditions.

One-Pot Direct Oxidation of Primary Amines to Carboxylic Acids through Tandem ortho-Naphthoquinone-Catalyzed and TBHP-Promoted Oxidation Sequence

Biomimetic oxidation of primary amines to carboxylic acids has been developed where the copper-containing amine oxidase (CuAO)-like o-NQ-catalyzed aerobic oxidation was combined with the aldehyde dehydrogenase (ALDH)-like TBHP-mediated imine oxidation protocol. Notably, the current tandem oxidation strategy provides a new mechanistic insight into the imine intermediate and the seemingly simple TBHP-mediated oxidation pathways of imines. The developed metal-free amine oxidation protocol allows the use of molecular oxygen and TBHP, safe forms of oxidant that may appeal to the industrial application.

Crosslinking Efficacy and Cytotoxicity of Genipin and Its Activated Form Prepared by Warming It in a Phosphate Buffer: A Comparative Study

The aim of the present study was to compare the acute and cumulative cytotoxicity of intact (n-GE) and warmed genipin (w-GE), while investigating the differences in crosslinking capabilities of these two genipins by rheological and mechanical tests. The n-GE solution was prepared by dissolving genipin powder in a sodium phosphate buffer solution. The w-GE solution was prepared by warming the n-GE solution at 37 °C for 24 h. The mechanical tests for chitosan (CH)/genipin gels showed the crosslinking rate of w-GE was much greater than that of n-GE up until 6 h after preparation, whereas the degree of crosslinking of CH/n-GE gels became higher at 12 h. The ISO 10993-5 standard method, which is established specifically for evaluating cumulative cytotoxicity, determined equivalent IC50 for w-GE (0.173 mM) and n-GE (0.166 mM). On the other hand, custom-made cytotoxicity tests using a WST-8 assay after 1 h of cultivation showed that the acute cytotoxicity of w-GE was significantly higher than that of n-GE at concentrations between 0.1–5 mM. The acute cytotoxicity of w-GE should be taken into consideration in its practical uses, despite the fact that the much faster crosslinking of w-GE is useful as an effective cross linker for in-situ forming gels.

Variant Aldehyde Dehydrogenase 2 (ALDH2*2) as a Risk Factor for Mechanical LA Substrate Formation and Atrial Fibrillation with Modest Alcohol Consumption in Ethnic Asians

Aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphism is a common genetic variant in Asians that is responsible for defective toxic aldehyde and lipid peroxidation metabolism after alcohol consumption. The extent to which low alcohol consumption may cause atrial substrates to trigger atrial fibrillation (AF) development in users with ALDH2 variants remains to be determined. We prospectively enrolled 249 ethnic Asians, including 56 non-drinkers and 193 habitual drinkers (135 (70%) as ALDH2 wild-type: GG, rs671; 58 (30%) as ALDH2 variants: G/A or A/A, rs671). Novel left atrial (LA) mechanical substrates with dynamic characteristics were assessed using a speckle-tracking algorithm and correlated to daily alcohol consumption and ALDH2 genotypes. Despite modest and comparable alcohol consumption by the habitual alcohol users (14.3 [8.3~28.6] and 12.3 [6.3~30.7] g/day for those without and with ALDH2 polymorphism, p = 0.31), there was a substantial and graded increase in the 4-HNE adduct and prolonged PR, and a reduction in novel LA mechanical parameters (including peak atrial longitudinal strain (PALS) and phasic strain rates (reservoir, conduit, and booster pump functions), p < 0.05), rather than an LA emptying fraction (LAEF) or LA volume index across non-drinkers, and in habitual drinkers without and with ALDH2 polymorphism (all p < 0.05). The presence of ALDH2 polymorphism worsened the association between increasing daily alcohol dose and LAEF, PALS, and phasic reservoir and booster functions (all P_interaction: <0.05). Binge drinking superimposed on regular alcohol use exclusively further worsened LA booster pump function compared to regular drinking without binge use (1.66 ± 0.57 vs. 1.97 ± 0.56 1/s, p = 0.001). Impaired LA booster function further independently helped to predict AF after consideration of the CHARGE-AF score (adjusted 1.68 (95% CI: 1.06–2.67), p = 0.028, per 1 z-score increment). Habitual modest alcohol consumption led to mechanical LA substrate formation in an ethnic Asian population, which was more pronounced in subjects harboring ALDH2 variants. Impaired LA booster functions may serve as a useful predictor of AF in such populations.

Repurposing brewery contaminant yeast as production strains for low-alcohol beer fermentation

A number of fungal isolates were recently obtained from a survey of the microbiota of multiple breweries and brewery products. Here, we sought to explore whether any of these brewery contaminants could be repurposed for beneficial use in beer fermentations, with particular focus on low-alcohol beer. There were 56 yeast strains first screened for the utilization of different carbon sources, ability to ferment brewer's wort, and formation of desirable aroma compounds. A number of strains appeared maltose-negative and produced desirable aromas without obvious off-flavours. These were selected for further scaled-up wort fermentations. The selected strains efficiently reduced wort aldehydes during fermentation, thus eliminating undesirable wort-like off-flavours, and produced a diverse volatile aroma profile. Two strains, Trigonopsis cantarellii and Candida sojae, together with a commercial Saccharomycodes ludwigii reference strain, were selected for 30-L-scale wort fermentations based on aroma profile and similarity to a commercial reference beer during sensory analysis using projective mapping. Both strains performed comparably to the commercial reference, and the T. cantarellii strain in particular, produced low amounts of off-flavours and a significantly higher amount of the desirable monoterpene alcohol trans-geraniol. The strain was also sensitive to common food preservatives and antifungal compounds and unable to grow at 37°C, suggesting it is relatively easily controllable in the brewery, and appears to have low risk of pathogenicity. This study shows how the natural brewery microbiota can be exploited as a source of non-conventional yeasts for low-alcohol beer production.

Metal-Free Chemoselective Oxidation of 4-Methylquinolines into Quinoline-4-Carbaldehydes

A convenient protocol for the synthesis of quinoline-4-carbaldehydes via chemoselective oxidation of 4-methylquinolines using hypervalent iodine(III) reagents as oxidant is described. This method highlights metal-free and mild reaction conditions, nice yield, good functional group tolerance, and high chemoselectivity.

Diversity of Carbonyl Compounds in Biogas and Natural Gas Revealed Using High-Resolution Mass Spectrometry and Nontarget Analysis

Airborne carbonyl compounds such as formaldehyde, acrolein, and methyl ethyl ketone have long been chemicals-of-concern in the environment due to their reactivity and their potential for negative health effects. Standard methods for determining carbonyls in air, which focus on a set of 15 or fewer compounds, involve derivatization to form nonvolatile hydrazones, which can readily be analyzed via liquid chromatography (LC) with ultraviolet detectors. Here, we apply a new LC-high-resolution mass spectrometry (HRMS) method to natural gas and a variety of upgraded biofuels to better assess their total carbonyl profile using the inherent selectivity of the standard sampling methodology and the selectivity and sensitivity of HRMS. The standard method accounted for only 64% of the total carbonyl content in natural gas and between 26 and 45% of the total carbonyl content in biogas sources, with the balance detected by the new LC/HRMS method. An additional 540 compounds with molecular formulas consistent with carbonyl compounds were detected compared to only 14 target compounds using the standard method. These results demonstrate that the established method dramatically under-reports both the total carbonyl load and the diversity of carbonyl species in natural gas and biogas samples.

Annotation of 1350 Common Genetic Variants of the 19 ALDH Multigene Family from Global Human Genome Aggregation Database (gnomAD)

Human aldehyde dehydrogenase (ALDH) is a multigene family with 19 functional members encoding a class of diverse but important enzymes for detoxification or biotransformation of different endogenous and exogenous aldehyde substrates. Genetic mutations in the ALDH genes can cause the accumulation of toxic aldehydes and abnormal carbonyl metabolism and serious human pathologies. However, the physiological functions and substrate specificity of many ALDH genes are still unknown. Although many genetic variants of the ALDH gene family exist in human populations, their phenotype or clinical consequences have not been determined. Using the most comprehensive global human Genome Aggregation Database, gnomAD, we annotated here 1350 common variants in the 19 ALDH genes. These 1350 common variants represent all known genetic polymorphisms with a variant allele frequency of ≥0.1% (or an expected occurrence of ≥1 carrier per 500 individuals) in any of the seven major ethnic groups recorded by gnomAD. We detailed 13 types of DNA sequence variants, their genomic positions, SNP ID numbers, and allele frequencies among the seven major ethnic groups worldwide for each of the 19 ALDH genes. For the 313 missense variants identified in the gnomAD, we used two software algorithms, Polymorphism Phenotyping (PolyPhen) and Sorting Intolerant From Tolerant (SIFT), to predict the consequences of the variants on the structure and function of the enzyme. Finally, gene constraint analysis was used to predict how well genetic mutations were tolerated by selection forces for each of the ALDH genes in humans. Based on the ratio of observed and expected variant numbers in gnomAD, the three ALDH1A gene members, ALDH1A1, ALDH1A2, and ALDH1A3, appeared to have the lowest tolerance for loss-of-function mutations as compared to the other ALDH genes (# observed/# expected ratio 0.15–0.26). These analyses suggest that the ALDH1A1, ALDH1A2, and ALDH1A3 enzymes may serve a more essential function as compared with the other ALDH enzymes; functional loss mutations are much less common in healthy human populations than expected. This informatic analysis may assist the research community in determining the physiological function of ALDH isozymes and associate common variants with clinical phenotypes.

TRP Channels as Sensors of Aldehyde and Oxidative Stress

The transient receptor potential (TRP) cation channel superfamily comprises more than 50 channels that play crucial roles in physiological processes. TRP channels are responsive to several exogenous and endogenous biomolecules, with aldehydes emerging as a TRP channel trigger contributing to a cellular cascade that can lead to disease pathophysiology. The body is not only exposed to exogenous aldehydes via tobacco products or alcoholic beverages, but also to endogenous aldehydes triggered by lipid peroxidation. In response to lipid peroxidation from inflammation or organ injury, polyunsaturated fatty acids undergo lipid peroxidation to aldehydes, such as 4-hydroxynonenal. Reactive aldehydes activate TRP channels via aldehyde-induced protein adducts, leading to the release of pro-inflammatory mediators driving the pathophysiology caused by cellular injury, including inflammatory pain and organ reperfusion injury. Recent studies have outlined how aldehyde dehydrogenase 2 protects against aldehyde toxicity through the clearance of toxic aldehydes, indicating that targeting the endogenous aldehyde metabolism may represent a novel treatment strategy. An addition approach can involve targeting specific TRP channel regions to limit the triggering of a cellular cascade induced by aldehydes. In this review, we provide a comprehensive summary of aldehydes, TRP channels, and their interactions, as well as their role in pathological conditions and the different therapeutical treatment options.

Mn- and Co-Catalyzed Aminocyclizations of Unsaturated Hydrazones Providing a Broad Range of Functionalized Pyrazolines

Manganese- and cobalt-catalyzed aminocyclization reactions of unsaturated hydrazones are reported. Whereas manganese catalysis provides access to pyrazoline and tetrahydropyridazine alcohols, cobalt catalysis for the first time paves the way for the selective formation of pyrazoline aldehydes. Furthermore, various functional groups including hydroperoxide, thiol derivatives, iodide, and bicyclopentane may be introduced via manganese-catalyzed ring-forming aminofunctionalization. A progesterone receptor antagonist was prepared using the aminocyclization protocol.

A sustainable approach towards the three-component synthesis of unsubstituted 1H-imidazoles in the water at ambient conditions

A green protocol for the synthesis of unsubstituted imidazoles has been demonstrated herein. The reaction is realized using commercially available lipase enzyme, porcine pancreas lipase (PPL) in water. The reaction conditions are selective and mild which helped to tolerate a wide variety of functional groups to give the desired products in good chemical yields.[Formula: see text].

Indoor air quality in shopping and storage areas

In retail stores, workers are constantly exposed to new manufactured goods. The issue of the exposure of retail workers to volatile organic compounds (VOCs) should clearly be considered. Therefore, this study provides data regarding VOC concentrations in ten French retail stores. The stores were chosen to represent various products: sports goods, shoes and leather, furniture, car equipment, bazaars, online-sales storage, clothes, books, DIY (do-it-yourself), and household appliances. VOCs and aldehydes were actively sampled on the same day in five to seven locations per building and outdoors. Toluene and formaldehyde were omnipresent with indoor concentrations reaching 252 and 53 µg/m³ , respectively. The car equipment store, followed by clothing, shoes, and leather, and DIY stores showed the worst indoor air quality. High concentrations were measured, for example, the maximum α-pinene concentration in the furniture and DIY stores was 364 and 141 µg/m³ , respectively, and the heptane concentration in the car equipment store reached 1,316 µg/m³ . Two VOCs classified as toxic to reproduction were measured: hexane in the car equipment store and the bazaar, and dimethylformamide in the sports goods store. This study shows some disparities in the indoor concentrations among different locations in the same store, particularly between sales and storage areas.

The Bucherer-Bergs Multicomponent Synthesis of Hydantoins-Excellence in Simplicity

Hydantoins and their hybrids with other molecules represent a very important group of heterocycles because they exhibit diverse biological and pharmacological activities in medicinal and agrochemical applications. They also serve as key precursors in the chemical or enzymatic synthesis of significant nonnatural α-amino acids and their conjugates with medical potential. This review provides a comprehensive treatment of the synthesis of hydantoins via the Bucherer-Bergs reaction including the Hoyer modification but limited to free carbonyl compounds or carbonyl compounds protected as acetals (ketals) and cyanohydrins used as starting reaction components. In this respect, the Bucherer-Bergs reaction provides an efficient and simple method in the synthesis of important natural products as well as for the preparation of new organic compounds applicable as potential therapeutics. The scope and limitations, as well as a comparison with some other methods for preparing hydantoins, are also discussed.

A Multifunctional Au/CeO2-Mg(OH)2 Catalyst for One-Pot Aerobic Oxidative Esterification of Aldehydes with Alcohols to Alkyl Esters

Au nanoparticles bound to crystalline CeO2 nanograins that were dispersed on the nanoplate-like Mg(OH)2, denoted as Au/CeO2-Mg(OH)2, were developed as the highly active and selective multifunctional heterogeneous catalyst for direct oxidative esterification of aldehydes with alcohols to produce alkyl esters under base-free aerobic conditions using oxygen or air as the green oxidants. Au/CeO2-Mg(OH)2 converted 93.3% of methacrylaldehyde (MACR) to methyl methacrylate (MMA, monomer of poly(methyl methacrylate)) with 98.2% selectivity within 1 h, and was repeatedly used over eight recycle runs without regeneration. The catalyst was extensively applied to other aldehydes and alcohols to produce desirable alkyl esters. Comprehensive characterization analyses revealed that the strong metal-support interaction (SMSI) among the three catalytic components (Au, CeO2, and Mg(OH)2), and the proximity and strong contact between Au/CeO2 and the Mg(OH)2 surface were prominent factors that accelerated the reaction toward a desirable oxidative esterification pathway. During the reaction, MACR was adsorbed on the surface of CeO2-Mg(OH)2, upon which methanol was simultaneously activated for esterifying the adsorbed MACR. Hemiacetal-form intermediate species were subsequently produced and oxidized to MMA on the surface of the electron-rich Au nanoparticles bound to partially reduced CeO2-x with electron-donating properties. The present study provides new insights into the design of SMSI-induced supported-metal-nanoparticles for the development of novel, multifunctional, and heterogeneous catalysts.

Algae to angiosperms: Autofluorescence for rapid visualization of plant anatomy among diverse taxa

PREMISE

Fluorescence microscopy is an effective tool for viewing plant internal anatomy. However, using fluorescent antibodies or labels hinders throughput. We present a minimal protocol that takes advantage of inherent autofluorescence and aldehyde-induced fluorescence in plant cellular and subcellular structures to markedly increase throughput in cellular and ultrastructural visualization.

METHODS AND RESULTS

Twelve species distributed across the plant phylogeny were each subjected to five fixative treatments: 1% paraformaldehyde and 2% glutaraldehyde, 2% paraformaldehyde, 2% glutaraldehyde, formalin-acid-alcohol (FAA), and 70% ethanol. Samples were prepared by embedding and mechanically sectioning or via whole mount. A confocal laser scanning system was used to collect micrographs. We evaluated and compared fixative influence on sample structural preservation and tissue autofluorescence.

CONCLUSIONS

Formaldehyde fixation of Viridiplantae taxa samples generates useful structural data while requiring no additional histological staining or clearing. In addition, a fluorescence-capable microscope is the only specialized equipment required for image acquisition. The minimal protocol developed in this experiment enables high-throughput sample processing by eliminating the need for multi-day preparations.

Fluorine-18 labeled aldehydes as prosthetic groups for oxime coupling with a FVIIa protein

New ¹⁸ F-labeled nonvolatile aldehyde prosthetic groups derived from [¹⁸ F]F-Py-TFP and spirocyclic iodonium (III)ylide precursors for late stage ¹⁸ F-labeling were developed. These precursors were characterized, ¹⁸ F-labeled, and compared in reactivity for oxime coupling. Oxime coupling was performed on an amino-oxy modified inhibited factor VII (FVIIai-ONH₂ ) in low concentration to prove the applicability of the proposed method.

Fingerprinting triacylglycerols and aldehydes as identity and thermal stability indicators of camellia oil through chemometric comparison with olive oil

Camellia oil is widely recognized as a high-quality culinary oil in East Asia for its organoleptic and health-promoting properties, but its chemical composition and thermal stability have not been comprehensively defined by comparisons with other oils. In this study, the triacylglycerols (TAGs) in camellia, olive, and six other edible oils were profiled by the liquid chromatography-mass spectrometry (LC-MS)-based chemometric analysis. Besides observing the similarity between camellia oil and olive oil, TAG profiling showed that OOO, POO, and OOG (O: oleic acid, P: palmitic acid, and G: gadoleic acid) can jointly serve as the identity markers of camellia oil. Thermal stability of virgin camellia oil (VCO) was further evaluated by extensive comparisons with virgin olive oil (VOO) in common lipid oxidation indicators, aldehyde production, and antioxidant and pro-oxidant contents. The results showed that p-anisidine value (AnV) was the sensitive lipid oxidation indicator, and C9-C11 aldehydes, including nonanal, 2-decenal, 2,4-decadienal, and 2-undecenal, were the most abundant aldehydes in heated VCO and VOO. Under the frying temperature, heated VCO had lower AnV and less aldehydes than heated VOO. Interestedly, the VCO had lower levels of pro-oxidant components, including α-linolenic acid, free fatty acids, and transition metals, as well as lower levels of antioxidants, including α-tocopherol and phenolics, than the VOO. Overall, great similarities and subtle differences in TAG and aldehyde profiles were observed between camellia and olive oils, and the thermal stability of camellia oil might be more dependent on the balance among its unsaturation level, pro-oxidant, and antioxidant components than a single factor.

Single-Crystal Cobalt Phosphide Nanorods as a High-Performance Catalyst for Reductive Amination of Carbonyl Compounds

The development of metal phosphide catalysts for organic synthesis is still in its early stages. Herein, we report the successful synthesis of single-crystal cobalt phosphide nanorods (Co₂P NRs) containing coordinatively unsaturated Co-Co active sites, which serve as a new class of air-stable, highly active, and reusable heterogeneous catalysts for the reductive amination of carbonyl compounds. The Co₂P NR catalyst showed high activity for the transformation of a broad range of carbonyl compounds to their corresponding primary amines using an aqueous ammonia solution or ammonium acetate as a green amination reagent at 1 bar of H₂ pressure; these conditions are far milder than previously reported. The air stability and high activity of the Co₂P NRs is noteworthy, as conventional Co catalysts are air-sensitive (pyrophorous) and show no activity for this transformation under mild conditions. P-alloying is therefore of considerable importance for nanoengineering air-stable and highly active non-noble-metal catalysts for organic synthesis.