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Field experiments were conducted in early summer 2004 by caging brown trout (Salmo trutta m. lacustris) in Southern Lake Saimaa (SE Finland) for 10 days. Cages were positioned into two depths at four distances (5 to 17 km) from the pulp and paper mill; one set with direct contact to the sediment and other locating at the three meters' depth from the water surface. Resin acids were measured from sediment, water, and fish bile. Possible toxicities were investigated by measuring liver EROD-activity, HSP70-protein, and gene expression profiles by microarray. The concentration of resin acids in the sediment showed clear gradient along the distance from the mill, and their concentrations in water ranged approximately from one to 30 microg L(-1). In the trout bile, concentrations were higher near the surface than on the bottom, indicating the role of current releases as sources of resin acids. When compared to trout held upstream from the effluent source, no differences were found in liver EROD nor HSP70 in bottom cages. However, near surface, a slight but statistically significant increase in EROD and HSP70 was found. Altogether 145 genes were found to be differentially regulated at downstream sites when compared 10 km upstream from the mill. The numbers of genes at each site varied from 5 to 45 without consistent differences between bottom and surface cages. Overall, neither expression profiles nor composition of the transcription signatures made possible to conclude an overt toxicity in exposed brown trout.

This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show an improved stability towards the mechanical degradation of the MoSx catalyst. [ABSTRACT FROM AUTHOR]

The current luminescent metal-organic framework (MOF) based fluorescence detection mostly focuses on achiral molecules. The stereospecific recognition and determination of MOF-based detection remain challenging. A novel luminescent terbium-based MOF (Tb-MOF) based biosensing system with excellent performance for stereoselective detection of D-amino acids (D-AAs) was introduced in this paper. D-Amino acid oxidase catalyzes stereospecific oxidative deamination of D-AAs, producing H2O2. The generated H2O2 effectively quenches the fluorescence of Tb-MOF. Under optimum conditions, the D-AAs were detected with excellent efficiency. The linear working range was 0.5-100 mM for D-Alanine (D-Ala) and 0. 5-5 mM for D-Proline (D-Pro), respectively. The limit of detection (Ksv detection) for D-Ala and D-Pro was 0.09 mM and 0.14 mM, respectively. The detection can be performed within 30 min with high selectivity and long-term stability. The fluorescent sensing platform required simple fabrication and operation and was free from complicated reaction processes and expensive reagents. The present sensing system was successfully applied in D-AA detection in human serum with good recovery, indicating its potential application in detection in biological samples. [ABSTRACT FROM AUTHOR]

Solubilization of plant nutrients from silicate rocks, using acids produced by microorganisms has emerged as both an environmentally friendly and an economically viable process for fertilizer production. In this work, biogenic acid was produced using Acidithiobacillus thiooxidans and elemental sulfur, and used it to solubilize K from verdete (Ve) and phonolite (Fo) rocks, comparing its solubilization efficiency to that of commercial sulfuric acid at 1 : 2 and 1 : 5 rock : acid ratios. After acid solubilization, the Ve and Fo rocks were chemically and morphologically characterized using several techniques. Agronomic performances of biogenic K-fertilizers derived from Ve and Fo were evaluated in a sequential corn–soybean–millet cropping system. Acid type and rock : acid ratio influenced the solubilization of K species from the rocks. Overall, biogenic acid led to a higher solubilization of K species in water and in citric acid than commercial sulfuric acid. The amount of solubilized K was higher at a 1 : 5 rock : acid ratio. Total dry matter yield and total K uptake by the crops increased as K rates increased and varied among K sources. Ve and Fo biogenic K-fertilizers provided higher amounts of available K to the crops than their in natura forms (rocks). The effect of acid solubilization was more notorious for Ve rock, significantly increasing the value of its acidified product as a fertilizer. Thus, our data demonstrate that biogenic acid produced by A. thiooxidans using elemental sulfur is a promising alternative to leach out K from silicate rocks. [ABSTRACT FROM AUTHOR]

An effective approach to separate chiral (2S,4S)-1-(tert-butoxy carbonyl)-4-(methoxymethyl) pyrrolidine-2-carboxylic acid ((2S,4S)-TBMP)) from mixed (2S,4S)-TBMP and (2S,4R)-1-(tert-butoxy carbonyl)-4-(methoxymethyl) pyrrolidine-2-carboxylic acid ((2S,4R)-TBMP), an important intermediate for the anti-HCV drug Velpatasvir, was developed for the first time, eliminating the need for salinization and dissociation processes and several organic solvents with water. Conceivable binding modes were set up by Gaussian calculation, and the separation process was designed and studied based on the calculation. The results showed that only the monohydrate of (2S,4S)-TBMP could be crystallized since three hydrogen bonds were formed between (2S,4S)-TBMP and water, which resulted in more stability and isomer separation. Compared to the original approach, our new approach exhibits a remarkable 17.4% increase in yield, a 43.3% rise in atom economy (AE), a 43.3% improvement in reaction mass efficiency (RME), and a substantial 32.0 g g−1 reduction in process mass intensity (PMI). An industrial-scale implementation was set up successfully according to the new approach, achieving a batch capacity of 100 kg. [ABSTRACT FROM AUTHOR]

In this paper, we present four Co-MOFs using R-substituted isophthalic acid (R-H2BDC, R = H, OH and COOH) along with trigonal n-TBT (n = 3 or 4) as organic ligands. These Co-MOFs are formulated as {[Co(1,3-BDC)(4-TBT)2/3]·(H2O)(DMF)1.5}n (Co-MOF-1), {[Co(HO-BDC)(4-TBT)]·(EtOH)2(DMF)2}n (Co-MOF-2), {[Co(HO-BDC)(4-TBT)2/3]·(H2O)3(MeOH)3(DMA)}n (Co-MOF-3) and {[Co3(BTC)2(3-TBT)2(H2O)2]·(H2O)2(EtOH)5(DMA)1.5}n (Co-MOF-4), where H2BDC = isophthalic acid, OH–H2BDC = 5-hydroxyisophthalic acid and H3BTC = 1,3,5-tricarboxybenzene, 4-TBT = 1,3,5- tris(4-pyridyl)benzene and 3-TBT = 1,3,5-tris(3-pyridyl)benzene. Co-MOF-1, 2 and 3 are constructed from the dimeric Co2(COO)2 unit and exhibit 3D frameworks. In Co-MOF-4, the dimeric Co2(COO)2 unit and single nuclear CoII center are connected by BTC3− and 3-TBT ligands into a 3D network. The catalytic experiments revealed that four Co-MOFs can catalyze the oxidative coupling reaction of benzyl alcohols and aniline to imines with good to excellent conversions under solvent-free conditions and an air atmosphere. Co-MOF-4 exhibited the best catalytic performance and the catalyst could be reused for at least five cycles without losing its structural integrity and catalytic activity. [ABSTRACT FROM AUTHOR]

Correction for 'Supramolecular self-assembly of amantadine hydrochloride with ferulic acid via dual optimization strategy establishes a precedent of synergistic antiviral drug-phenolic acid nutraceutical cocrystal' by Ling-Yang Wang et al., Analyst, 2021, 146, 3988–3999, https://doi.org/10.1039/D1AN00478F. [ABSTRACT FROM AUTHOR]

This article describes the synthesis of four new co-crystals obtained via cross-crystallisation of 2- and 4-mercaptopyridines with thiourea and trithiocyanuric acid and examines their crystal structures. The resulting structures are the first four reported co-crystals of mercaptopyridines. In one case, the synthesis resulted in the production of a ternary co-crystal of unexpected composition instead of the desired product and the correct co-crystal needed to be obtained under dark room conditions; interestingly, when separated from solution, all four co-crystal samples were fully light resistant. The crystal state of the four co-crystals is stabilized by several N–H⋯S type hydrogen bonds. Additionally, in the case of thiourea co-crystals, additional short contacts of S⋯S type are also observed. This relatively complicated network of intermolecular interactions is fully characterized herein. [ABSTRACT FROM AUTHOR]

Three MnII complexes, named Mn2(HATNA)2(CH3OH)4 (1), {[Mn3(ATNA)2(DMF)2(H2O)2]·0.5DMF·0.5H2O}n (2, DMF = N,N-dimethylformamide), and {[Mn6(ATNA)4(H2O)10]·8DMSO·2.5H2O}n (3, DMSO = dimethyl sulphoxide), were successfully synthesized by the reaction of the ligand azotetrazole-3-hydroxy-2-naphthoic acid (H3ATNA) and Mn(CH3COO)2 in CH3OH, DMF, and DMSO, respectively. A binuclear structure was found for complex 1, with the two Mn(II) ions doubly bridged through N–N linkers from the two tetrazole rings. Both 2 and 3 displayed one-dimensional structures. Magnetic studies show that antiferromagnetic interactions of Mn(II) ions existed in complexes 1–3. All the complexes exhibited luminescence emission peaks at room temperature. [ABSTRACT FROM AUTHOR]

With the development of pure organic room-temperature phosphorescence (ORTP), study in excitation-dependent fluorescence-phosphorescence (ExDFPh) dual emission materials is burgeoning. Herein, using formylphenylboronic acid (FPBA) as a prototype, the effect of substitution position on the ExDFPh properties was investigated. Among the three isomers, 4-FPBA exhibits outstanding ExDFPh behavior. Its luminescence color could turn from yellow to white to blue through decreasing the excitation energy. Importantly, dual phosphorescence-emitting species were observed and verified, which updates the understanding of the RTP mechanism. The difference in the ExDFPh behavior is possibly attributed to the RTP performance which is drastically affected by substitution position. Crystal analyses reveal that the intermolecular hydrogen-bond interaction changes from two to one to zero-dimension with varying substitution patterns from para- to meta- to ortho-position, which would affect the RTP emission. This is further proved by the comparison with the corresponding boronic ester, which contains no typical hydrogen bonds in the crystal structure. Theoretical calculation indicates that the intermolecular interaction would also play an important role in the intersystem crossing of the higher-lying singlet excited state. Based on the multi-color emission, potential application in anticounterfeiting is exhibited. [ABSTRACT FROM AUTHOR]

Clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics have been considered a next-generation molecular diagnosis tool. Single-readout mode has been extensively employed in massive CRISPR/Cas12a-based biosensors. In this work, we propose a one-tube dual-readout biosensor (CRISAT) for the first time for the detection of ultrasensitive nucleic acids and non-nucleic acids developed by harnessing CRISPR-ALP tandem assay. In the presence of a target, Cas12a is activated to randomly cut the single-stranded hyDNA sequence of MB@hyDNA-cALP, thus releasing abundant alkaline phosphatase (ALP) in the supernatant solution. By using 4-aminophenol phosphate as the substrate of ALP, p-aminophenol is produced, which then reacts with N-[3-(trimethoxysilyl)propyl]ethylenediamine or diethylenetriamine to generate silicon-containing polymer carbon dots (Si PCDs) or polymer carbon dots (PCDs) in situ, which can be observed by the naked eye or detected using a fluorescent device in the same solution. Using this strategy, a fluorescence and colorimetry dual-readout nanoplatform for CRISPR-based biosensors can be rationally developed. We ascertain the applicability of CRISAT by detecting the SARS-CoV-2 pseudovirus, achieving superior sensitivity and specificity. With simple modification of crRNAs, the CRISAT platform can also be employed to detect monkeypox virus (MPXV) and non-nucleic acids of adenosine triphosphate (ATP). This work shows great potential for the detection of nucleic acids and non-nucleic acids. [ABSTRACT FROM AUTHOR]

Recently, ionic liquids have been widely used for chiral separation. However, several papers have reported the use of ionic liquids as the sole chiral selector. In this work, a novel capillary electrophoresis method using the ionic liquid 3-methyl-1-(3-sulfopropyl)-1H-imidazol-3-ium lactobionate (MSI-LA) as a chiral selector was developed for the enantioseparation of propranolol, metoprolol, bisoprolol, esmolol, atenolol, sotalol, terbutaline and clenbuterol. Method optimization was conducted and the optimized method (40 mM borax buffer, v/v 30% methanol, pH 8.5, 160 mM MSI-LA; +10 kV voltage; capillary temperature, 15 °C; 50 mbar/5 s injection; detection wavelength, 230 nm) was successful for the baseline separation of the eight basic drugs. The LA (lactobionic acid) system was compared. The possible mechanisms of enantioseparation were investigated using molecular modeling. Both the cation and anion of MSI-LA provided interactions between the chiral selector and analytes, and finally enhanced chiral recognition capability compared with LA. [ABSTRACT FROM AUTHOR]

Quinaldic acids are important fine chemicals. Nowadays, industrial methods to synthesize quinaldic acids rely heavily on a three-step process established based on the Reissert reaction, which involves however the use of highly toxic potassium cyanide. In this paper, a novel cyclization of aniline with ethyl 4,4-diethoxycrotonate was realized, which offered ethyl quinaldate in good yield. Based on this reaction, an eco-efficient method to prepare quinaldic acids was developed, which involves the following three steps: (i) synthesis of ethyl 4,4-diethoxycrotonate through photooxidation of furfural and a consecutive ring-opening alcoholysis; (ii) cyclization of ethyl 4,4-diethoxycrotonate with aniline, and (iii) hydrolysis of the generated ethyl quinaldate. This new method not only avoids the use of toxic potassium cyanide but also meets many salient features of green chemistry, such as the use of bio-based feedstocks, environmentally benign metal-free conditions and good reaction yields. [ABSTRACT FROM AUTHOR]

Valorization of cellulose, hemicellulose, and lignin into value-added industrially relevant chemicals is important to achieve sustainability goals that various governments and industries have set. In view of this, the oxidative synthesis of 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethyl furfural (HMF) as an analogous compound to terephthalic acid in the synthesis of PEF is interesting to researchers. Though advancements in the oxidation of HMF have been made, the efficient synthesis of HMF, its storage, and isolation are great challenges due to its instability under normal conditions. While purified HMF can be used to synthesize FDCA, it is imperative to use crude HMF for the synthesis of FDCA since several techno-economical studies reveal that the purification of HMF is the most cost-intensive step. Herein, we demonstrate the oxidation of crude HMF, synthesized in the laboratory to FDCA, using nonprecious-based mixed metal oxides in the aqueous medium in the presence of oxygen/air. Among various catalysts, Cu–Mn catalyst at 120 °C within 8 h in the presence of oxygen (10 bar) could yield 90% FDCA. This activity was comparable with that of the commercially available and well-studied Ru/C (5 wt%) catalyst (93% yield). In addition, the role of HMF purity, air as an oxidant, and the influence of temperature, pressure, and time is systematically studied. It is also demonstrated that FDCA formation proceeds via HMFCA and FFCA formation. The isolation of FDCA and its purity (>99%) is corroborated with various techniques such as NMR, IR, and HRMS. [ABSTRACT FROM AUTHOR]

Simple switching of the site-selectivity of C–H activation reactions of substrates containing multiple directing groups is particularly important for the so-called late stage functionalization synthetic approach. In this work, we verified the possibility of achieving this by adding acids of different strengths. Using a substrate containing two differently strong (and basic) directing groups, the influence of the addition of acids on the regioselectivity of the C–H activation step of the reaction with palladium acetate was thoroughly studied. The addition of no or weak acids results in cyclopalladation being controlled by a stronger directing group. However, the addition of a strong acid causes protonation of this group and the reaction is then controlled by a weaker directing group. Finally, this approach enables double C–H activation leading to a unique class of compounds: "non-symmetrical" [2.2]-dipalladaparacyclophanes. [ABSTRACT FROM AUTHOR]

Waste toner with high carbon content has the potential to become a carbon material, but its utilization is limited due to the low carbonization yield. In this work, a carbon-based solid acid was prepared by carbonization and sulfonation of waste toner with the aid of sulfuric acid. The characterization of its structure and the evaluation of its properties revealed that sulfuric acid played three roles in the process of carbon-based solid acid prepared from waste toner (WT-CSA). Specifically, this method not only solved the problem of low yield of carbon precursor (CP) obtained by carbonization of waste toner but also introduced thiophene sulfur into the aromatic carbon flakes during the carbonization process. Moreover, thiophene sulfur makes the sulfonation easier, thus increasing the density of –SO3H. In addition, the activity and cyclic stability of the catalyst were evaluated by cellulose hydrolysis. The results show that the catalyst exhibits excellent hydrolytic activity and hydrothermal stability. [ABSTRACT FROM AUTHOR]

5-Methyl-2-furancarboxylic acid (MFA) is an important substituted furoic acid with versatile applications. However, its synthesis processes are not green and efficient. Here, we report a novel route to the sustainable synthesis of MFA from bio-renewable 5-hydroxymethyl-2-furancarboxylic acid (HMFA) by the direct cleavage of the C-5-Methyl-2-furancarboxylic acid (MFA) is an important substituted furoic acid with versatile applications. However, its synthesis processes are not green and efficient. Here, we report a novel route to the sustainable synthesis of MFA from bio-renewable 5-hydroxymethyl-2-furancarboxylic acid (HMFA) by the direct cleavage of the C-OH bond in HMFA at ambient temperature. Active carbon (C)-supported Pd catalysts exhibited high efficiency and stability in HMFA hydrogenolysis to MFA, providing a high yield of 94.5% at 30 °C and 3.0 MPa H2 in tetrahydrofuran. Such a high efficiency of Pd/C was found to be related to the strong adsorption of HMFA on the C support surfaces, most likely via their π-π interactions. This work provides an efficient strategy for the selective cleavage of the α-C-OH bonds in the furan ring under mild conditions and the sustainable production of MFA and its derivatives from biomass resources. OH bond in HMFA at ambient temperature. Active carbon (C)-supported Pd catalysts exhibited high efficiency and stability in HMFA hydrogenolysis to MFA, providing a high yield of 94.5% at 30 °C and 3.0 MPa H2 in tetrahydrofuran. Such a high efficiency of Pd/C was found to be related to the strong adsorption of HMFA on the C support surfaces, most likely via their π-π interactions. This work provides an efficient strategy for the selective cleavage of the α-C-OH bonds in the furan ring under mild conditions and the sustainable production of MFA and its derivatives from biomass resources. [ABSTRACT FROM AUTHOR]

A novel butterfly-shaped tetracarboxylic acid [9,9′-methylene-bis(9-methylfluorene-2,7-dicarboxylic acid), H4L] featuring a co-facial bifluorene core was designed and synthesised. Reactions of H4L with CdII produced the luminescent supramolecular frameworks 2 and 3, with different dimensionalities and wingspans of L4−. Their solid-state emission properties were rationalised based on the torsional dynamics of the facing bifluorene units by means of X-ray diffraction analysis and TD-DFT calculations. [ABSTRACT FROM AUTHOR]

Substituent size and isomerization play an important role in the polymorphism of 2-(naphthalen-n-ylamino)-benzoic acids (n = 1, 2; 2-NBAs) as each of the two previously investigated 2-NBAs was found to be polymorphic, while their parent compound fenamic acid (FA) has only one form discovered. 2-(Naphthalen-1-ylamino)-nicotinic acid (1) and 2-(naphthalen-2-ylamino)-nicotinic acid (2) (2-NNA) are isosteric compounds of 2-NBAs, and 2-(2,3-dimethyl-phenylamino)-nicotinic acid (3) and 2-(3,4-dimethyl-phenylamino)-nicotinic acid (4) are 2-NNA analogues with similar substitution patterns. All four compounds are clonixin analogues. The polymorphism of these four compounds was investigated. One solvent-free form (1-A) and one hydrate (1-H) were discovered for 1, three forms (2-I, 2-II, and 2-III) were obtained for 2, and one form was found for 3 and 4. The four systems were characterized by single-crystal XRD (SCXRD) and powder XRD (PXRD), and structural properties were compared among the crystals of the four compounds, their isosteres, and other related analogues. The phase behavior of the four systems was studied with differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) was used to investigate the dehydration of 1-H. Computational studies such as stable conformer search, π–π interaction energy calculation, and non-covalent interaction (NCI) analysis were performed to shed light on the rise of polymorphism, and the relative contribution of various intermolecular interactions to the overall stability of the crystals. The study confirmed the effect of substituent size, thus the consequent π–π interactions, on the hydrate formation of compound 1 and polymorphism of compound 2. [ABSTRACT FROM AUTHOR]

A series of modified β-cyclodextrins (CDx's) with a mono/bis-quinoline tether was synthesized and used as chirogenic supramolecular hosts for mediating the enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (AC) at various pH. Based on the enantiodifferentiating results of the native CDx's, the modified derivatives significantly enhanced the chemical and optical yields of irregular photodimers 5 and 6. Interestingly, the flexible bis-quinoline tethered CDx derivative 10 and its N-methylated homolog 11 inverted the stereochemical outcome of syn-head-to-tail dimer 6 from 48.7 to −68.2% and 64.2 to −81.2%, respectively, upon changing the solution pH from 1 and 9. Binding models before and after pKa of the complex were proposed based on the photodimerization results, various spectroscopic studies and computational simulation. [ABSTRACT FROM AUTHOR]

As one of the representative secondary metabolites in fermentation processes and common additives in modern industry, kojic acid (KA) has been mired in controversy in recent years due to its potential toxicity and carcinogenicity. Hence, it is of high importance to develop novel analysis strategies for KA to surveil its rational utilization and ensure public health. Based on enzyme modulated sensitization of TiO2 NPs and the inhibition effect of KA towards tyrosinase (Tyr), we report a facile and sensitive photoelectrochemical (PEC) sensor for KA in food samples. On an operational level, this protocol excluded the tedious immobilization process of traditional PEC enzyme sensors, allowing the crucial catalysis and sensitization process to take place in a small centrifuge tube, making the experimental process concise and fast. Under optimized conditions, a linear detection range of 10−7 M to 10−3 M was achieved, with a detection limit of 3.2 × 10−8 M. Furthermore, the feasibility of the strategy in food samples was validated in vinegar and wheat flour. This protocol would hold great promise for real application in diverse food products, and offer a general prototype for future immobilization-free and quick analysis of other enzyme inhibitors. [ABSTRACT FROM AUTHOR]

Piperazine (Pipz) is widely used as a building block for the self-assembly of supramolecular hydrogen-bonded crystalline networks. Here, piperazine-1,4-diol (PipzDiol) has been suggested as an analog of piperazine with an extended H-bond donor geometry. A convenient synthesis of PipzDiol has been developed and the compound has been fully characterized. Structural and stereodynamic studies showed that PipzDiol exists in solution as a dynamic mixture of conformers/invertomers. The formation of co-crystals with acids is accompanied by preferable selection of one stereoisomeric form depending on the nature of the co-former. Piperazine and PipzDiol were found to form distinct supramolecular H-bonded networks with topologically different H-bonded motifs. In crystalline adducts with sulfuric, oxalic, and para-aminobenzoic acids, piperazine forms 3D H-bonded networks, while 2D layers are assembled with PipzDiol. [ABSTRACT FROM AUTHOR]

A transition metal-catalyzed carbene insertion strategy has been developed to activate the inactivated sp2 C–H bond of medicinally important cis-stilbene acids. This approach enables the facile construction of α-pyrone and chromene-2-one skeletons on the olefinic bond of cis-stilbene acid with high atom economy, good yield, broad functional group tolerance and gram-scale synthetic feasibility. The strategy unveils the efficiency of acid functionalities as directing groups along with sulfoxonium and hypervalent iodonium ylide as carbene precursors. The constructed architectures were explored for their photophysical properties showing emission ranging from 500 to 600 nm, and the biological potential was examined through molecular docking analysis and percentage inhibition studies. Additionally, ESI-MS studies were also performed to identify the key intermediates, helping to sketch a probable mechanism. [ABSTRACT FROM AUTHOR]

Simultaneous direct production of fuels and chemicals via photocatalytic biomass conversion is an effective strategy to achieve the carbon-neutral goal but no studies on the co-production of CO and xylonic acid have been reported. Here, an efficient CIS/GO@3D-OMA photocatalyst of CdIn2S4 (CIS) anchored on graphene oxide (GO) nanosheets in a three-dimensional ordered mesoporous aerogel was prepared and successfully used in the co-generation of CO and xylonic acid. Experimental results showed that CIS/GO@3D-OMA-3 has broad light absorption, high charge density, and fast charge space separation. Correspondingly, the CO and xylonic acid yield achieved 1213.88 μmol g−1 h−1 and 76.76% in the xylose system, respectively. Interestingly, the system is also applicable to xylan (CO: 187.20 μmol g−1 h−1; xylonic acid: 0.2 g gxylan−1). All h+, ˙OH, 1O2 and ˙O2− were conductive to CO and xylonic acid production, in which h+ played a primary role. This study provides a fresh perspective for biomass utilization. [ABSTRACT FROM AUTHOR]

A facile, metal- and additive-free C–C bond construction between imidazo[1,2-a]pyridines and coumarin-3-carboxylic acids through a decarboxylative Michael addition is reported to achieve an imidazo[1,2-a]pyridin-3-yl-chroman-2-one skeleton. In addition, heterocyclic polyaromatic dibenzoisochromenoimidazo[1,2-a]pyridin-6-ones of value for future medicinal chemistry can be obtained successfully by this procedure through a domino reaction involving Michael addition/decarboxylation/oxidation/C–H bond activation and annulation. [ABSTRACT FROM AUTHOR]

Two nanosized titanium-oxide clusters (TOCs), Ti12(μ2-O)14(μ3-O)4PA16 (1; PA = 2-picolinate) and Ti12(μ2-O)18PA18 (2) were synthesized by using 2-picolinic acid and Ti(OiPr)4 in one-pot reactions. Their structures were determined using single-crystal X-ray diffractometry. Although both have the same core composition of Ti12O18, 1 exhibited superior H2 evolution activity of up to 180 μmol h−1 g−1, which is nearly eight times faster than 2. Mechanism studies revealed that 1 could induce the assembly of 2.3 nm PtNPs into 10–30 nm supra-nanoparticle structures, which contributed to the increased H2 evolution rate. [ABSTRACT FROM AUTHOR]

Most conformational molecular switches based on an amide skeleton are limited in their use in solution. We developed a molecular switch with an amide skeleton, which is applicable without a solvent. Treatment of solid 3 with HCl vapor (without dissolution) and sublimation switched the amide conformation by converting a dimethylamino group to a dimethylammonium group. The transformation was reversed by sublimation with pumping to remove HCl. This switching, which proceeds in the gas state in sublimation and not the solution state, was confirmed to be an on/off process by crystal analysis. [ABSTRACT FROM AUTHOR]

A straightforward and sustainable approach for the 1,2-addition of propiolic acids to ynamide has led to bench-stable sp2 (E)-enol-enamides of enediynes and dienynes. The reaction is chemo-, regio-, and stereoselective and does not require metal catalysts and solvent. The ynamide motif is extremely amenable to functionalization in the presence of the tethered alkyne triple bond. The synthetic technique is operationally simple; no hydrolysis of ketenimine species occurs under acidic conditions. The transformation tolerates a wide range of common functional groups, constructing a library of highly functionalized 1,5,5′/6′-enediynes and 1,5,5′-dienynes of sp2 (E)-N,O-acetal skeletons. [ABSTRACT FROM AUTHOR]

The gold catalysed alkynediol spiroketalization to assemble the central spiro-bis-THF fragments (C22–C33 and C36–C47) of symbiospirols A–C is documented. The adopted chiral pool approach employed commercially available D -glucose and L -malic acid in the synthesis of key building blocks. In addition, two other possible diastereomers have been synthesized in order to establish the relative stereochemistry of the unassigned THF-center of symbiospirols B/C. [ABSTRACT FROM AUTHOR]

Electrochemical conversion of biomass-derived intermediate compounds to high-value products has emerged as a promising approach in the field of biorefinery. Biomass upgrading allows for the production of chemicals from non-fossil-based carbon sources and capitalization on electricity as a green energy input. Amino acids, as products of biomass upgrading, have received relatively little attention. Pharmaceutical and food industries will benefit from an alternative strategy for the production of amino acids that does not rely on inefficient fermentation processes. The use of renewable biomass resources as starting materials makes this proposed strategy more desirable. Herein, we report an electrochemical approach for the selective oxidation of biomass-derived α-hydroxyl acids to α-keto acids, followed by electrochemical reductive amination to yield amino acids as the final products. Such a strategy takes advantage of both reactions at the anode and cathode and produces amino acids under ambient conditions with high energy efficiency. A flow electrolyzer was also successfully employed for the conversion of α-hydroxyl acids to amino acids, highlighting its great potential for large-scale application. [ABSTRACT FROM AUTHOR]

Aldonic acids have already found many applications in food, pharmaceutical, and cosmetics industries and there are many new ones likely to come. One of the limiting factors, which stalls further research and uses of this broad class of sugar acids, is a lack of efficient and environmentally friendly production methods. Here we report a novel bi-enzymatic thionine-mediated PQQ-dependent glucose dehydrogenase and heme peroxidase system that allows efficient production of aldonic acids. Structurally diverse aldoses, including mono-, di-, and oligosaccharides, can be oxidized this way to the corresponding aldonic acids. The reaction proceeds under mild conditions – water solution and ambient temperature. Due to the total turnover number of PQQ-dependent dehydrogenase reaching 3.5 × 106 (for lactose), the developed method is very efficient. This allows a space–time yield up to 11 g (L h)−1 (for xylose), making the overall process industrially attractive. [ABSTRACT FROM AUTHOR]

Correction for 'An optical sensor for the sensitive determination of formaldehyde gas based on chromotropic acid and 4-aminoazobenzene immobilized in a hydrophilic membrane' by M. D. Fernández-Ramos et al., Analyst, 2023, 148, 4533–4538, https://doi.org/10.1039/D3AN01056B. [ABSTRACT FROM AUTHOR]

Retraction of 'Ruthenium(II) CNN Pincer Complexes as Efficient Catalysts in Oxidative Annulation of Aromatic Acids with Alkynes to Isocoumarins' by Periasamy Viswanathamurthi et al., New J. Chem., 2023, https://doi.org/10.1039/D3NJ03745B. [ABSTRACT FROM AUTHOR]

Kynurenic acid is a by-product of tryptophan metabolism in humans, with abnormal levels indicative of disease. There is a need for water-soluble receptors that selectively bind kynurenic acid, allowing for detection and quantification. We report here the high-affinity binding of kynurenic acid in aqueous media to a resorcinarene salt receptor decorated with four flexible naphthalene groups at the upper rim. Experimental results from 1H NMR, isothermal titration calorimetry, and electronic absorption and fluorescence spectroscopies all support high-affinity binding and selectivity for kynurenic acid over tryptophan. The measured binding constant (K = 1.46 ± 0.21 × 105 M−1) is one order of magnitude larger than that observed with other resorcinarene receptors. The present host–guest system can be employed for sensory recognition of kynurenic acid. Computational studies reveal the key role of a series of cooperative attractive intra- and inter-molecular interactions contributing to an optimal binding process in this system. [ABSTRACT FROM AUTHOR]

Optically pure 6-fluoro-chroman-2-carboxylic acids (FCCAs), with (S) and (R)-configurations, are pivotal chiral building blocks in the pharmaceutical industry. To date, the production of (S) and (R)-FCCAs mainly depends on chemical resolution, which is a complex, low yield, and highly polluting process. Here, we present a practical enzymatic resolution method of FCCAs based on two esterases, EstS and EstR, isolated from Geobacillus thermocatenulatus. Using the racemic methyl 6-fluoro-chroman-2-carboxylate (MFCC) as the substrate in an aqueous-toluene biphasic system, (S) and (R)-FCCAs were produced by EstS and EstR catalysis with an enantiomeric excess (ee) value >99% and 95-96%, respectively, and the highly enantioselective mechanisms were revealed by molecular simulations. To simplify the resolution process and enhance the productivity, we further designed an innovative methodology for the "sequential biphasic batch resolution" of MFCC with immobilized cells. In each batch, only the aqueous phase needs to be replaced to sequentially change the immobilized cells of EstS or EstR and recover optically pure FCCAs in turn, while the organic phase was retained and MFCC was continually supplemented after every two batches. In this study, ten batches of sequential resolution were performed, and 229.3 mM (S)-FCCAs with 96.9% ee, and 224.1 mM (R)-FCCAs with 99.1% ee were obtained in 40 h, affording a 93.5% total mole yield. This is the first reported enzymatic resolution technique of FCCAs, and represents significant advantages over those chemical resolution methods. [ABSTRACT FROM AUTHOR]

Surface functionalized titania particles are obtained using a high energy planetary ball mill. A parameter that is often overseen while applying this technique is the grinding bowl and grinding sphere material which has a crucial influence on the energy impact in the milling process. In this paper we describe the influence of the grinding bowl focusing on a zirconia ceramic material and comparing the results with experiments performed using a WC/Co-hard metal grinding bowl. The degrees of surface coverage as well as tribochemical phase transitions are dependent on the grinding bowl material. Due to the lower density of ZrO2-ceramic the overall energy input is lower. As a result the surface coverage and amount of phase transition decreased when using a zirconia ceramic grinding bowl instead of the WC/Co-hard metal grinding bowl. Lower impurity concentration in the final material was achieved due to the better abrasion behavior of the zirconia grinding bowl. [ABSTRACT FROM AUTHOR]

Cu/Fe-mediated arylation of pyridines with arylboronic acids, featuring a low-cost catalytic system and an easy operation, is disclosed. A series of length-controllable linear (the number of aryls ranges from 2 to 6) and L-shaped pyridinium salts have been easily prepared by this N(sp2)-arylation and they show tunable fluorescence emission that is mainly tailored by the length of the N-aryl rather than C-aryl groups. Furthermore, direct N-alkenylation of sp2-nitrogen heterocycles is reported. Moreover, the AIE, pH-responsive and electrochromic properties of the relevant pyridinium salts are researched. [ABSTRACT FROM AUTHOR]

Glucaric acid is regarded as a top-value added compound from biomass, however, due to prevalent lactonization, the recovery of purified glucaric acid is challenging. Accordingly, an efficient method for glucaric acid separation, especially its diacid form, is necessary to facilitate its valorization. Here, we report a robust separation process that produces glucaric acid crystals from fermentation broth. This process first recovers purified monopotassium glucarate from broth and then recovers purified glucaric acid through acidification and antisolvent crystallization. Isopropanol was found to be an effective antisolvent reducing the solubility of glucaric acid while concomitantly forming an azeotrope with water. This allows solvent removal at low temperature through azeotropic drying, which avoids lactonization, and thus prevents impurities in the resulting crystals. Overall, this process was found to separate monopotassium glucarate and glucaric acid with a recovery yield of >99.9% and 71% at purities of ca. 95.6 and 98.3%, respectively. Process modeling demonstrates the ability to recycle the antisolvents IPA and acetone with >99% recovery and determined the energy input to be ∼20 MJ kg−1 for isolation of monopotassium glucarate and 714 MJ kg−1 for glucaric acid (0.06 M). The approach detailed in this work is likely applicable to the separation of other highly oxygenated bio-carboxylic acids (e.g., mevalonic acid) from fermentation broths, as well as to their recovery from abiotic reaction solutions. [ABSTRACT FROM AUTHOR]

Spiro[3.3]heptane-2,6-dicarboxylic acid (Fecht's acid, H2SHDC) is examined as a non-aromatic terephthalic acid isostere for the first time. The rigid spirocyclic backbone provides greater steric bulk than conventional aromatic dicarboxylates with consequences for pore chemistry and control of interpenetration, presented here in the structures of two new MOFs. Complex 1 is a three-dimensional rod packed structure consisting of Yb-carboxylate chains bridged by SHDC linkers which, although non-porous, exhibits a surprisingly high thermal stability for a spirocyclic cyclobutane derivative. Complex 2 is a co-ligand complex of SHDC with trans-1,2-bis(4-pyridyl)ethene (bpe) which contains linear solvent channels despite fourfold interpenetration. Although the framework does not retain its structure following evacuation, a clear difference is observed in the extended structure compared to the structurally related terephthalate species. This observation suggests the non-aromatic backbone of Fecht's acid and other rigid aliphatic linkers may prove an effective means to disfavour deleterious close inter-framework contacts which prevail in interpenetrated aromatic MOFs. [ABSTRACT FROM AUTHOR]

High activity hyper-crosslinked polymer solid acids (HCPSAs) were prepared from different aromatic monomers, and the structure was regulated by selecting the type and size of aromatic monomers. The results indicated that aromatic monomers affect not only the skeleton structure of HCPSAs, but also the loading of active groups significantly. The structural change of HCPSAs displayed a certain regularity as the size of the aromatic monomer increased; however, the catalytic activity of HCPSAs in oleic acid methylation and cellulose hydrolysis exhibited a different trend. HCPSA derived from thiophene presented the highest oleic acid conversion, while HCPSA prepared from phenanthrene showed the highest reducing sugar yield. The highly active HCPSA for a specific reaction can be obtained by controlling aromatic monomers. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) is a biomass-derived feedstock that can be converted to a wide array of value-added products; several of these can be accessed efficiently by electrochemical conversion. Herein, we present a study of factors governing LA conversion in electrochemical environments. Most notably, we identify an unprecedentedly efficient pathway forming 4-hydroxyvaleric acid (HVA), a valuable monomer that can be used for production of bio-polyesters—specifically, poly(hydroxy acids)—as well as γ-valerolactone (GVL) (a green fuel/solvent) and other fine chemicals. This method shows >99.9% selectivity and >80% faradaic efficiency for conversion above 80%. Production rates higher than 40 g L−1 h−1 (or 200 kg L−1 mgeom.−2 h−1) were achieved; these are substantially higher than reports for compatible biochemical methods. We further identify mechanistic insights regarding the steering of selectivity toward this new pathway in comparison to known electrochemical routes toward valeric acid (VA) or to GVL. Finally, we provide a fast, sequential one-pot synthesis route to transform electrochemically-produced HVA to GVL with higher overall selectivity and faradaic efficiency than can be achieved by direct aqueous electrochemical conversion of LA to GVL (96% conversion and >99.9% selectivity, giving a total yield of 93% from LA). [ABSTRACT FROM AUTHOR]

Two series of both nitrogen-rich and thermostable energetic materials as well as their energetic salts based on hetarenecarboxylic acids are now described. Among these new compounds, neutral compounds 3 and 10 have higher nitrogen contents (69.66% and 63.05%) than their energetic salts, which suggests that they could be used as green energetic materials. In addition, compound 3 shows a good decomposition temperature (Td = 281 °C), which is close to that of TNT (Td = 295 °C). Nitrogen-rich salt 6 exhibits better integrated energetic-properties (D = 8913 m s−1, IS = 24 J, FS = 320 N) than RDX (D = 8795 m s−1, IS = 7.5 J, FS = 120 N). [ABSTRACT FROM AUTHOR]

A stable Ni2+ substituted TiO2 catalyst (Ti0.97Ni0.03O1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti1−xNixO2−x (x = 0.01–0.06) crystallizes in the TiO2 anatase structure with Ni2+ substituted in Ti4+ ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 105 h−1. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

An efficient palladium-catalyzed denitrogenative Suzuki–Miyaura type cross-coupling of 1,2,3-benzotriazin-4(3H)-ones with organoboronic acid is described. The reaction is compatible with various aryl and alkenyl boronic acids affording ortho-arylated and alkenylated benzamides in good to high yields. Heteroaromatic boronic acids were also successfully employed. Along with this, a coupling reaction was established by using phenyl boronate ester as the coupling partner. The reaction is believed to proceed via a five-membered aza-palladacyclic intermediate. DFT calculations were studied comparing the reactivity of palladium and nickel complexes in the five-membered aza-metallacycle formation from 1,2,3-benzotriazin-4(3H)-ones. The application of the reaction was successfully demonstrated by converting ortho-alkenylated products to ortho-alkylated products in high yields via a reduction reaction. [ABSTRACT FROM AUTHOR]

An efficient and novel method for the preparation of unnatural α-amino acids (UAAs) containing 7-hydroxy-2,2-dimethyl-chroman via a 1,3-di-polar-cyloaddition reaction has been described. Using this method, various new ethyl 2-amino-3-(3-(7-hydroxy-2,2-dimethylchroman-6-yl)isoxazol-5-yl)propanoate derivatives have been prepared where the isoxazole ring is acting as a linker between alanine and chroman moieties. This is the first example of isoxazole-tethered 2,2-dimethylchroman-amino acid hybrids. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is an intriguing way of biomass conversion. Herein, a sulfidation of nickel foam (Ni2S3/NF) was attempted via a hydrothermal method, achieving high selectivity and efficiency for HMF oxidation. The optimized Ni2S3/NF electrode exhibits a nearly 100% conversion of HMF, 98% yield of FDCA, and 94% high faradaic efficiency. This material is stable and retains activity after 6 consecutive measurements. This work provides a facile route to design and prepare electrocatalysts for biomass upgrading. [ABSTRACT FROM AUTHOR]

The rapid drug release and poor self-healing properties of drug-loaded hydrogels largely limit their practical application. Herein, we present a simple method to prepare hydrogels with self-healing, drug hosting and pH-sensitive properties for sustained drug release. First, salicylic acid was loaded into β-CD through host–guest interactions. The hydrogel was then constructed through the polymerization of acrylamide using cyclodextrin-phenylboronic acid as a reversible, pH-sensitive cross-linker. The obtained hydrogel exhibited outstanding stretchability (1150%), good tensile strength (42 kPa), excellent self-healing properties (90%) and high biocompatibility. Besides, the introduction of the cyclodextrin-phenylboronic acid cross-linker endowed the hydrogel with pH-sensitive and sustained drug release properties. These functions enable cyclodextrin-phenylboronic acid cross-linked hydrogels to be drug hosting, self-healing and pH-sensitive flexible materials for sustained drug release, making them a powerful platform for various biomedical applications. [ABSTRACT FROM AUTHOR]

Tolfenamic acid (TFA) is a very well-studied polymorphic compound with eight polymorphs discovered to date. Here, we report on a new polymorph of TFA, form IX, which was unexpectedly crystallised from isopropanol at low temperatures. Crystals of form IX appeared concomitantly with the more common forms I and II, raising the question as to why this polymorph had never been reported before. With the aid of dispersion corrected DFT, paired with calculations of vibrational frequencies, we analysed the stability of this new polymorphic form of TFA. Thermal measurements, solubility measurements and solvent-mediated phase transformation experiments confirm that TFA form IX is a metastable polymorph, with a stability that is close to the well-known forms I and II. [ABSTRACT FROM AUTHOR]

The acetic acid promoted reaction of 3-hydroxy-3-(indol-3-yl)indolin-2-ones and mercapto-substituted β-enamino esters showed very interesting molecular diversity. The reaction in ethanol at room temperature in the presence of acetic acid resulted in two diastereoisomeric 3,3-disubstituted oxindoles in high yields. When the reaction was carried out in refluxing ethanol, the reaction with 3-hydroxy-3-(indol-3-yl)indolin-2-ones with N-alkyl groups gave polycyclic spirooxindoles in satisfactory yields. However, a similar reaction with 3-hydroxy-3-(indol-3-yl)indolin-2-ones with NH groups afforded functionalized dihydroindolo[3,2-c]phenothiazines with sequential ring-opening of oxindole. A plausible domino annulation mechanism was rationally proposed for the formation of different kinds of polycyclic compounds. [ABSTRACT FROM AUTHOR]