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Serum 1 H NMR metabolomics has been used as a diagnostic tool for screening type 2 diabetes (T2D) with chronic kidney disease (CKD) as comorbidity. This work aimed to evaluate 1 H NMR data to detect the initial kidney damage and CKD in T2D subjects, through multivariate statistical analysis. Clinical data and biochemical parameters were obtained for classifying five experimental groups using KDIGO guidelines: Control (healthy subjects), T2D, T2D-CKD-mild, T2D-CKD-moderate, and T2D-CKD-severe. Serum 1 H NMR spectra were recorded to follow two strategies: one based on metabolite-to-creatinine (Met/Cr) ratios as targeted metabolomics, and the second one based on untargeted metabolomics from the 1 H NMR profile. A prospective biomarkers panel of the early stage of T2D-CKD based in metabolite-to-creatinine ratio (ornithine/Cr, serine/Cr, mannose/Cr, acetate/Cr, acetoacetate/Cr, formate/Cr, and glutamate/Cr) was proposed. Later, a statistical model based on non-targeted metabolomics was used to predict initial CKD, and its metabolic pathway analysis allowed identifying the most affected pathways: phenylalanine, tyrosine, and tryptophan biosynthesis; valine, leucine, and isoleucine degradation; glyoxylate and dicarboxylate metabolism; glycine, serine, and threonine metabolism; and histidine metabolism. Nonetheless, further studies with a larger cohort are advised to precise ranges in metabolite-to-creatinine ratios and evaluate the prediction pertinency to detect initial CKD in T2D patients in both statistical models proposed., Competing Interests: Declaration of Competing Interest Alma L. Saucedo reports financial support was provided by National Council for Science and Technology. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: The availability of soil phosphorus (P) often limits the productivities of wet tropical lowland forests. Little is known, however, about the metabolomic profile of different chemical P compounds with potentially different uses and about the cycling of P and their variability across space under different tree species in highly diverse tropical rainforests., Results: We hypothesised that the different strategies of the competing tree species to retranslocate, mineralise, mobilise, and take up P from the soil would promote distinct soil 31 P profiles. We tested this hypothesis by performing a metabolomic analysis of the soils in two rainforests in French Guiana using 31 P nuclear magnetic resonance (NMR). We analysed 31 P NMR chemical shifts in soil solutions of model P compounds, including inorganic phosphates, orthophosphate mono- and diesters, phosphonates, and organic polyphosphates. The identity of the tree species (growing above the soil samples) explained > 53% of the total variance of the 31 P NMR metabolomic profiles of the soils, suggesting species-specific ecological niches and/or species-specific interactions with the soil microbiome and soil trophic web structure and functionality determining the use and production of P compounds. Differences at regional and topographic levels also explained some part of the the total variance of the 31 P NMR profiles, although less than the influence of the tree species. Multivariate analyses of soil 31 P NMR metabolomics data indicated higher soil concentrations of P biomolecules involved in the active use of P (nucleic acids and molecules involved with energy and anabolism) in soils with lower concentrations of total soil P and higher concentrations of P-storing biomolecules in soils with higher concentrations of total P., Conclusions: The results strongly suggest "niches" of soil P profiles associated with physical gradients, mostly topographic position, and with the specific distribution of species along this gradient, which is associated with species-specific strategies of soil P mineralisation, mobilisation, use, and uptake., (© 2024. The Author(s).)

The direct and unambiguous detection and identification of individual metabolite molecules present in complex biological mixtures constitute a major challenge in (bio)analytical research. In this context, nuclear magnetic resonance (NMR) spectroscopy has proven to be particularly powerful owing to its ability to provide both qualitative and quantitative atomic-level information on multiple analytes simultaneously in a noninvasive manner. Nevertheless, NMR suffers from a low inherent sensitivity and, moreover, lacks selectivity regarding the number of individual analytes to be studied in a mixture of a myriad of structurally and chemically very different molecules, e.g., metabolites in a biofluid. Here, we describe a method that circumvents these shortcomings via performing selective, photochemically induced dynamic nuclear polarization (photo-CIDNP) enhanced NMR spectroscopy on unmodified complex biological mixtures, i.e., human urine and serum, which yields a single, background-free one-dimensional NMR spectrum. In doing this, we demonstrate that photo-CIDNP experiments on unmodified complex mixtures of biological origin are feasible, can be performed straightforwardly in the native aqueous medium at physiological metabolite concentrations, and act as a spectral filter, facilitating the analysis of NMR spectra of complex biofluids. Due to its noninvasive nature, the method is fully compatible with state-of-the-art metabolomic protocols providing direct spectroscopic information on a small, carefully selected subset of clinically relevant metabolites. We anticipate that this approach, which, in addition, can be combined with existing high-throughput/high-sensitivity NMR methodology, holds great promise for further in-depth studies and development for use in metabolomics and many other areas of analytical research.

The surface chemistry of Metal-Organic Polyhedra (MOPs) is crucial to their physicochemical properties because it governs how they interact with external substances such as solvents, synthetic organic molecules, metal ions, and even biomolecules. Consequently, the advancement of synthetic methods that facilitate the incorporation of diverse functional groups onto MOP surfaces will significantly broaden the range of properties and potential applications for MOPs. This study describes the use of copper(I)-catalysed, azide-alkyne cycloaddition (CuAAC) click reactions to post-synthetically modify the surface of alkyne-functionalised cuboctahedral MOPs. To this end, a novel Rh(II)-based MOP with 24 available surface alkyne groups was synthesised. Each of the 24 alkyne groups on the surface of the "clickable" Rh-MOP can react with azide-containing molecules at room temperature, without compromising the integrity of the MOP. The wide substrate catalogue and orthogonal nature of CuAAC click chemistry was exploited to densely functionalise MOPs with diverse functional groups, including polymers, carboxylic and phosphonic acids, and even biotin moieties, which retained their recognition capabilities once anchored onto the surface of the MOP., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The addition of two unsymmetric malonate esters to the Buckminster fullerene C 60 can lead to 22 spectroscopically distinguishable isomeric products and therefore represents a formidable synthesis challenge. In this work, we achieve 87 % selectivity for the formation of a single (in,out-trans-3) isomer by combining three approaches: (i) we use a starting material, in which the two malonates are covalently connected (tether approach); (ii) we form the strong supramolecular complex of C 60 with the shape-persistent [10]CPP macrocycle (template approach) and (iii) we embed this complex further within a self-assembled nanocapsule (shadow mask approach). Variation of the spacer chain shed light on the limitations of the approach and the ring dynamics in the unusual [2]catenanes were studied in silico with atomistic resolution. This work significantly widens the scope of mechanically interlocked architectures comprising cycloparaphenylenes (CPP)., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Spin crossover (SCO) complexes, through their reversible spin transition under external stimuli, can work as switchable memory materials. Here, we present a protocol for the synthesis and characterization of a specific polyanionic iron SCO complex and its diluted systems. We describe steps for its synthesis and the determination of crystallographic structure of the SCO complex in diluted systems. We then detail a range of spectroscopic and magnetic techniques employed to monitor the spin state of the SCO complex in both diluted solid- and liquid-state systems. For complete details on the use and execution of this protocol, please refer to Galán-Mascaros et al. 1 ., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Chiral 2-hydroxy acids and 2-hydroxy-4-butyrolactone derivatives are structural motifs often found in fine and commodity chemicals. Here, we report a tandem biocatalytic stereodivergent route for the preparation of these compounds using three stereoselective aldolases and two stereocomplementary ketoreductases using simple and achiral starting materials. The strategy comprises (i) aldol addition reaction of 2-oxoacids to aldehydes using two aldolases from E. coli , 3-methyl-2-oxobutanoate hydroxymethyltransferase (KPHMT Ecoli ), 2-keto-3-deoxy-l-rhamnonate aldolase (YfaU Ecoli ), and trans - o -hydroxybenzylidene pyruvate hydratase-aldolase from Pseudomonas putida (HBPA Pputida ) and (ii) subsequent 2-oxogroup reduction of the aldol adduct by ketopantoate reductase from E. coli (KPR Ecoli ) and a Δ 1 -piperidine-2-carboxylate/Δ 1 -pyrroline-2-carboxylate reductase from Pseudomonas syringae pv. tomato DSM 50315 (DpkA Psyrin ) with uncovered promiscuous ketoreductase activity. A total of 29 structurally diverse compounds were prepared: both enantiomers of 2-hydroxy-4-butyrolactone (>99% ee), 21 2-hydroxy-3-substituted-4-butyrolactones with the (2 R ,3 S ), (2S,3 S ), (2 R ,3 R ), or (2S,3 R ) configuration (from 60:40 to 98:2 dr), and 6 2-hydroxy-4-substituted-4-butyrolactones with the (2S,4 R ) configuration (from 87:13 to 98:2 dr). Conversions of aldol adducts varied from 32 to 98%, while quantitative conversions were achieved by both ketoreductases, with global isolated yields between 20 and 45% for most of the examples. One-pot one-step cascade reactions were successfully conducted achieving isolated yields from 30 to 57%., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Type 2 diabetes mellitus (DM2) is a multimorbidity, long-term condition, and one of the worldwide leading causes of chronic kidney disease (CKD) -a silent disease, usually detected when non-reversible renal damage have already occurred. New strategies and more effective laboratory methods are needed for more opportune diagnosis of DM2-CKD. This study comprises clinical parameters and nuclear magnetic resonance (NMR)-based urine metabolomics data from 60 individuals (20-65 years old, 67.7% females), sorted in 5 experimental groups (healthy subjects; diabetic patients without any clinical sign of CKD; and patients with mild, moderate, and severe DM2-CKD), according to KDIGO. DM2-CKD produces a continuous variation of the urine metabolome, characterized by an increase/decrement of a group of metabolites that can be used to monitor CKD progression (trigonelline, hippurate, phenylalanine, glycolate, dimethylamine, alanine, 2-hydroxybutyrate, lactate, and citrate). NMR profiles were used to obtain a statistical model, based on partial least squares analysis (PLS-DA) to discriminate among groups. The PLS-DA model yielded good validation parameters (sensitivity, specificity, and area under the curve (AUC) of the receiver operating characteristic curve (ROC) plot: 0.692, 0.778 and 0.912, respectively) and, thus, it can differentiate between subjects with DM2-CKD in early stages, from subjects with a mild or severe condition. This metabolic signature exhibits a molecular variation associated to DM2-CKD, and data suggests it can be used to predict risk of DM2-CKD in patients without clinical signs of renal disease, offering a new alternative to current diagnosis methods., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Cobalt-catalyzed C-H amination via M-nitrenoid species is spiking the interest of the research community. Understanding this process at a molecular level is a challenging task, and here we report a well-defined macrocyclic system featuring a pseudo- O h aryl-Co III species that reacts with aliphatic azides to effect intramolecular C sp2 -N bond formation. Strikingly, a putative aryl-Co═NR nitrenoid intermediate species is formed and is rapidly trapped by a carboxylate ligand to form a carboxylate masked-nitrene, which functions as a shortcut to stabilize and guide the reaction to productive intramolecular C sp2 -N bond formation. On one hand, several intermediate species featuring the C sp2 -N bond formed have been isolated and structurally characterized, and the essential role of the carboxylate ligand has been proven. Complementarily, a thorough density functional theory study of the C sp2 -N bond formation mechanism explains at the molecular level the key role of the carboxylate-masked nitrene species, which is essential to tame the metastability of the putative aryl-Co III ═NR nitrene species to effectively yield the C sp2 -N products. The solid molecular mechanistic scheme determined for the C sp2 -N bond forming reaction is fully supported by both experimental and computation complementary studies.

Water pollution threatens human and environmental health worldwide. Thus, there is a pressing need for new approaches to water purification. Herein, we report a novel supramolecular strategy based on the use of a metal-organic polyhedron (MOP) as a capture agent to remove nitrogenous organic micropollutants from water, even at very low concentrations (ppm), based exclusively on coordination chemistry at the external surface of the MOP. Specifically, we exploit the exohedral coordination positions of Rh II -MOP to coordinatively sequester pollutants bearing N-donor atoms in aqueous solution, and then harness their exposed surface carboxyl groups to control their aqueous solubility through acid/base reactions. We validated this approach for removal of benzotriazole, benzothiazole, isoquinoline, and 1-napthylamine from water., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Three enzymatic routes toward γ-hydroxy-α-amino acids by tandem aldol addition-transamination one-pot two-step reactions are reported. The approaches feature an enantioselective aldol addition of pyruvate to various nonaromatic aldehydes catalyzed by trans - o -hydroxybenzylidene pyruvate hydratase-aldolase (HBPA) from Pseudomonas putida . This affords chiral 4-hydroxy-2-oxo acids, which were subsequently enantioselectively aminated using S -selective transaminases. Three transamination processes were investigated involving different amine donors and transaminases: (i) l-Ala as an amine donor with pyruvate recycling, (ii) a benzylamine donor using benzaldehyde lyase from Pseudomonas fluorescens Biovar I (BAL) to transform the benzaldehyde formed into benzoin, minimizing equilibrium limitations, and (iii) l-Glu as an amine donor with a double cascade comprising branched-chain α-amino acid aminotransferase (BCAT) and aspartate amino transferase (AspAT), both from E. coli , using l-Asp as a substrate to regenerate l-Glu. The γ-hydroxy-α-amino acids thus obtained were transformed into chiral α-amino-γ-butyrolactones, structural motifs found in many biologically active compounds and valuable intermediates for the synthesis of pharmaceutical agents., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

Chirality plays a fundamental role in nature, but its detection and quantification still face many limitations. To date, the enantiospecific analysis of mixtures necessarily requires prior separation of the individual components. The simultaneous enantiospecific detection of multiple chiral molecules in a mixture represents a major challenge, which would lead to a significantly better understanding of the underlying biological processes; for example, via enantiospecifically analysing metabolites in their native environment. Here, we report on the first in situ enantiospecific detection of a thirty-nine-component mixture. As a proof of concept, eighteen essential amino acids at physiological concentrations were simultaneously enantiospecifically detected using NMR spectroscopy and a chiral solvating agent. This work represents a first step towards the simultaneous multicomponent enantiospecific analysis of complex mixtures, a capability that will have substantial impact on metabolism studies, metabolic phenotyping, chemical reaction monitoring, and many other fields where complex mixtures containing chiral molecules require efficient characterisation., (© 2020 Wiley-VCH GmbH.)

The congested nature of quaternary carbons hinders their preparation, most notably when stereocontrol is required. Here we report a biocatalytic method for the creation of quaternary carbon centers with broad substrate scope, leading to different compound classes bearing this structural feature. The key step comprises the aldol addition of 3,3-disubstituted 2-oxoacids to aldehydes catalyzed by metal dependent 3-methyl-2-oxobutanoate hydroxymethyltransferase from E. coli (KPHMT) and variants thereof. The 3,3,3-trisubstituted 2-oxoacids thus produced were converted into 2-oxolactones and 3-hydroxy acids and directly to ulosonic acid derivatives, all bearing gem -dialkyl, gem -cycloalkyl, and spirocyclic quaternary centers. In addition, some of these reactions use a single enantiomer from racemic nucleophiles to afford stereopure quaternary carbons. The notable substrate tolerance and stereocontrol of these enzymes are indicative of their potential for the synthesis of structurally intricate molecules.

Productivity of tropical lowland moist forests is often limited by availability and functional allocation of phosphorus (P) that drives competition among tree species and becomes a key factor in determining forestall community diversity. We used non-target 31 P-NMR metabolic profiling to study the foliar P-metabolism of trees of a French Guiana rainforest. The objective was to test the hypotheses that P-use is species-specific, and that species diversity relates to species P-use and concentrations of P-containing compounds, including inorganic phosphates, orthophosphate monoesters and diesters, phosphonates and organic polyphosphates. We found that tree species explained the 59% of variance in 31 P-NMR metabolite profiling of leaves. A principal component analysis showed that tree species were separated along PC 1 and PC 2 of detected P-containing compounds, which represented a continuum going from high concentrations of metabolites related to non-active P and P-storage, low total P concentrations and high N:P ratios, to high concentrations of P-containing metabolites related to energy and anabolic metabolism, high total P concentrations and low N:P ratios. These results highlight the species-specific use of P and the existence of species-specific P-use niches that are driven by the distinct species-specific position in a continuum in the P-allocation from P-storage compounds to P-containing molecules related to energy and anabolic metabolism.

Herein, we perform for the first time a preliminary NMR and computational study of the spiroglycol structure. Spiroglycol is a highly symmetrical molecule, but it should be chiral due to the presence of a chiral axis. The presence of two enantiomers was demonstrated performing NMR enantiodifferentiation experiments using α,α'-bis(trifluoromethyl)-9,10-anthracenedimethanol (ABTE) as a chiral solvating agent (CSA). The addition of 0.6 equiv of ABTE allows the differentiation of several spiroglycol proton signals. The lack of resolution observed in the proton spectrum can be tackled through the corresponding 13 C NMR spectrum where a significant enantiodifferentiation at the spirocarbon atom was observed. In order to physically separate both enantiomers, a SPG derivatization with camphorsulfonic acid and Mosher's acid was performed affording the corresponding diastereoisomeric ester mixtures. Computations performed with the Gaussian16 package showed that the enantiodifferentiation is mainly due to the different compound thermodynamics stability.

Heteronuclear long-range scalar coupling constants ( n J CH ) are a valuable tool for solving problems in organic chemistry and are especially suited for stereochemical and configurational analyses of small molecules and natural products. This tutorial will focus on the step-by-step implementation of several 2D 1 H frequency selective HSQMBC experiments for the easy and accurate measurement of either the magnitude or both the magnitude and the sign of long-range n J CH couplings. The performance of these experiments will be showcased with several scenarios in a range of different experimental conditions., (© 2019 John Wiley & Sons, Ltd.)

The detection of ultra-long-range ( 4 J CH and higher) heteronuclear connectivities can complement the conventional use of HMBC/HSQMBC data in structure elucidation NMR studies of proton-deficient natural products, where two-bond and three-bond correlations are usually observed. The performance of the selHSQMBC experiment with respect to its broadband HSQMBC counterpart is evaluated. Despite its frequency-selectivity nature, selHSQMBC efficiently prevents any unwanted signal phase and intensity modulations due to passive proton-proton coupling constants typically involved in HSQMBC. As a result, selHSQMBC offers a significant sensitivity enhancement and provides pure in-phase multiplets, improving the detection levels for short- and long-range cross-peaks corresponding to small heteronuclear coupling values. This is particularly relevant for experiments optimized to small n J CH values (2-3 Hz), referred to as LR-selHSQMBC, where key cross-peaks that are not visible in the equivalent broadband LR-HSQMBC spectrum can become observable in optimum conditions.

A novel series of complexes of the formula [Ru(4,4'-X 2 -bpy) 2 (Mebpy-CN)](PF 6 ) 2 (X = -CH 3 , -OCH 3 , -N(CH 3 ) 2 ; Mebpy-CN = 4-methyl-2,2'-bipyridine-4'-carbonitrile) have been synthesized and characterized by spectroscopic, electrochemical, and photophysical techniques. Inclusion of the electron-withdrawing substituent -CN at one bpy ligand and different electron-donor groups -X at the 4,4'-positions of the other two bpy ligands produce a fine tuning of physicochemical properties. Redox potentials, electronic absorption maxima, and emission maxima correlate well with Hammett's σ p parameters of X. Quantum mechanical calculations are consistent with experimental data. All the complexes can be anchored through the nitrile moiety of Mebpy-CN over ZnO nanowires in dye-sensitized solar cells that exhibit an improvement of light to electrical energy conversion efficiency as the electronic asymmetry increases in the series., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

A new persistent organic free radical has been synthetized with Br atoms occupying the ortho- and para-positions of a trityl core. After the isolation of its two propeller-like atropisomers, Plus (P) and minus (M), their absolute configurations were assigned by a combination of theoretical and experimental data. Remarkably, no hints of racemization were observed up to 60 °C for more than two hours, due to the higher steric hindrance imposed by the bulky Br atoms. Therefore, when compared to its chlorinated homologue (t 1/2 =18 s at 60 °C), an outstanding stability against racemization was achieved. A circularly polarized luminescence (CPL) response of both enantiomers was detected. This free radical shows a satisfactory luminescent dissymmetry factor (|g lum (592 nm)|≈0.7×10 -3 ) despite its pure organic nature and low luminescence quantum yield (LQY). Improved organic magnetic CPL emitters derived from the reported structure can be envisaged thanks to the wide possibilities that Br atoms at para-positions offer for further functionalization., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The optimum detection and accurate measurement of longer-range ( 4 J and higher) heteronuclear NMR correlations is described. The magnitude and/or the sign of a wide range of large and small long-range couplings can be simultaneously determined for protonated and non-protonated 13 C and 15 N nuclei using the LR-selHSQMBC experiment., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Natural brassinosteroids possess a 22 R , 23 R configuration that appears essential for biological activity. It is, therefore, interesting to elucidate if the activity of brassinosteroids with a short side chain depends on the C22 configuration. Herein, we describe the synthesis of new brassinosteroids analogs with 24-norcholane type of side chain and R configuration at C22. The initial reaction is the dihydroxylation of a terminal olefin that leads to S / R epimers. Three different methods were tested in order to evaluate the obtained S/R ratio and the reaction yields. The results indicate that Upjohn dihydroxylation is the most selective reaction giving a 1.0:0.24 S / R ratio, whereas a Sharpless reaction leads to a mixture of 1.0:0.90 S / R with 95% yield. Using the latter mixture and following a previous reported method, benzoylated derivatives and both S and R brassinosteroids analogs were synthesized. All synthesized compounds were completely characterized by NMR spectroscopy, and HRMS of new compounds are also given. In conclusion, a synthetic route for preparation of new analogs of brassinosteroids of 24-norcholane type and R configuration at C22 were described. It is expected that this will help to elucidate if a configuration at C22 is a structural requirement for hormonal growth activity in plants.

Combining an electrophilic iron complex [Fe( F pda)(THF)] 2 (3) [ F pda=N,N'-bis(pentafluorophenyl)-o-phenylenediamide] with the pre-activation of α-alkyl-substituted α-diazoesters reagents by LiAl(OR F ) 4 [OR F =(OC(CF 3 ) 3 ] provides unprecedented access to selective iron-catalyzed intramolecular functionalization of strong alkyl C(sp 3 )-H bonds. Reactions occur at 25 °C via α-alkyl-metallocarbene intermediates, and with activity/selectivity levels similar to those of rhodium carboxylate catalysts. Mechanistic investigations reveal a crucial role of the lithium cation in the rate-determining formation of the electrophilic iron-carbene intermediate, which then proceeds by concerted insertion into the C-H bond., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nitrogen heterocycles are structural motifs found in many bioactive natural products and of utmost importance in pharmaceutical drug development. In this work, a stereoselective synthesis of functionalized N-heterocycles was accomplished in two steps, comprising the biocatalytic aldol addition of ethanal and simple aliphatic ketones such as propanone, butanone, 3-pentanone, cyclobutanone, and cyclopentanone to N -Cbz-protected aminoaldehydes using engineered variants of d-fructose-6-phosphate aldolase from Escherichia coli (FSA) or 2-deoxy-d-ribose-5-phosphate aldolase from Thermotoga maritima (DERA Tma ) as catalysts. FSA catalyzed most of the additions of ketones while DERA Tma was restricted to ethanal and propanone. Subsequent treatment with hydrogen in the presence of palladium over charcoal, yielded low-level oxygenated N-heterocyclic derivatives of piperidine, pyrrolidine and N-bicyclic structures bearing fused cyclobutane and cyclopentane rings, with stereoselectivities of 96-98 ee and 97:3 dr in isolated yields ranging from 35 to 79%., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Commonly used DFT methods for the calculation of 1JCH coupling constants have typically required the application of ad hoc correction factors, modification of functionals, or empirical scaling to improve the fit between predicted and experimental values. Here we demonstrate that highly accurate 1JCH coupling predictions can be obtained without such adjustments by careful selection of DFT methods for geometry optimization and J-coupling calculations (e.g. B3LYP/6-31G(d,p)(mixed)//mPW1PW/cc-pVTZ). The proposed method was cross-validated against a diverse set of 122 1JCH couplings and was successfully applied to the conformational and stereochemical analysis of strychnine and a previously unreported trachylobane diterpene natural product.

The practical aspects of some NMR experiments designed for the simultaneous acquisition of 2D COSY and 2D TOCSY spectra are presented and discussed. Several techniques involving afterglow-based, coherence transfer pathway (CTP)-based, and NMR by Ordered Acquisition using 1 H-detection (NOAH)-based strategies for the collection of different free-induction signal decays (FIDs) within the same scan are evaluated and compared. These methods offer a faster recording of these spectra in small-molecule NMR when sensitivity is not a limiting factor, with a reduction in spectrometer time about 45-60% when compared with the conventional sequential acquisition of the parent experiments. It is also shown how the optimized design of an extended three-FID approach yields one COSY and two TOCSY spectra simultaneously by combining CTP and NOAH principles in the same experiment, affording substantial sensitivity enhancements per time unit., (© 2019 John Wiley & Sons, Ltd.)

A time-efficient NMR strategy that involves the interleaved acquisition of two 2D HSQC spectra having different spectral widths in the indirect 13 C dimension is presented. We show how the two equivalent coherence transfer pathways involved in sensitivity-enhanced HSQC experiments are managed selectively and detected separately in different FID periods within the same scan. The feasibility of this new SADA-HSQC (Spectral Aliasing in Dually Acquired HSQC) technique is demonstrated by recording simultaneously two complementary datasets, conventional and highly-resolved spectral-aliased 2D HSQC spectra, in a single NMR experiment. Combining the information from both datasets, accurate chemical shift determination and excellent signal dispersion is achieved in a unique measurement using only few t 1 increments., (Copyright © 2019 Elsevier Inc. All rights reserved.)

A dual NMR data acquisition strategy to handle and detect two active equivalent transfer pathways is presented and discussed. We illustrate the power of this time-efficient approach by collecting two different 2D spectra simultaneously in a single experiment: i) TOCSY or HSQC-TOCSY spectra with different mixing times, ii) F2- 13 C-coupled and decoupled HSQC spectra, iii) conventional and pure-shift HSQC spectra, or iv) complementary HSQC and HSQC-TOCSY spectra., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The concepts of pure-shift NMR and time-shared NMR are merged in a single experiment. A 13 C/ 15 N time-shared version of the real-time BIRD-based broadband homodecoupled HSQC experiment is described. This time-efficient approach affords simultaneously 1 H- 13 C and 1 H- 15 N pure-shift HSQC spectra in a single acquisition, while achieving substantial gains in both sensitivity and spectral resolution. We also present a related 13 C/ 15 N-F2-coupled homodecoupled version of the CLIP-HSQC experiment for the simultaneous measurement of 1 J CH and 1 J NH from the simplified doublets observed along the direct dimension. Finally, a novel J-resolved HSQC experiment has been designed for the simple and automated determination of both 1 J CH / 1 J NH from a 2D J-resolved spectrum., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The development of new tools to improve the quality of nuclear magnetic resonance (NMR) spectra is a challenging task. The concept of "perfect NMR" includes the design of robust pulse sequences that allow an investigator to obtain undistorted pure in-phase signals, with pure absorption lineshapes that are free of phase anomalies derived from undesired J modulations. Here, alternative NMR building blocks to the spin-echo that are based on a general double SE module, known as a perfect-echo, are reviewed. Several implementations to minimize/remove unwanted dispersive contributions in homonuclear and heteronuclear NMR experiments are described and illustrated with some examples of broad interest for small molecules., (© 2018 John Wiley & Sons, Ltd.)

Multiple-FID acquisition (MFA) within the same scan is applied to acquire simultaneously multiple 2D spectra from a single NMR experiment. A discussion on the incorporation of the MFA strategy in several homonuclear and heteronuclear 2D pulse sequences is presented. As a proof of concept, a set of novel COSY, TOCSY and HMBC experiments are reported as a time-efficient solution in small-molecule NMR spectroscopy.

1,n-ADEQUATE is a powerful NMR technique for elucidating the structure of proton-deficient small molecules that can help establish the carbon skeleton of a given molecule by providing long-range three-bond 13 C─ 13 C correlations. Care must be taken when using the experiment to identify the simultaneous presence of one-bond 13 C─ 13 C correlations that are not filtered out, unlike the HMBC experiment that has a low-pass J-filter to filter 1 J CH responses out. Dual-optimized, inverted 1 J CC 1,n-ADEQUATE is an improved variant of the experiment that affords broadband inversion of direct responses, obviating the need to take additional steps to identify these correlations. Even though ADEQUATE experiments can now be acquired in a reasonable amount of experimental time if a cryogenic probe is available, low sensitivity is still the main impediment limiting the application of this elegant experiment. Here, we wish to report a further refinement that incorporates real-time bilinear rotation decoupling-based homodecoupling methodology into the dual-optimized, inverted 1 J CC 1,n-ADEQUATE pulse sequence. Improved sensitivity and resolution are achieved by collapsing homonuclear proton-proton couplings from the observed multiplets for most spin systems. The application of the method is illustrated with several model compounds., (Copyright © 2018 John Wiley & Sons, Ltd.)

A 1 H- 1 H total correlation spectroscopy (TOCSY) experiment incorporating 13 C multiplicity information is proposed. In addition, broadband 1 H homodecoupling in the indirect dimension can be implemented using a perfect BIRD module that affords exclusive 1 H chemical shift evolution with full decoupling of all heteronuclear and homonuclear (including 2 J HH ) coupling constants. As a complement to the normal TOCSY and the recent PSYCHE-TOCSY experiments, this novel multiplicity-edited TOCSY experiment distinguishes between CH/CH 3 (phased up) and CH 2 (phased down) cross-peaks, which facilitates resonance analysis and assignment., (Copyright © 2017 John Wiley & Sons, Ltd.)

Asymmetric aldol addition of simple aldehydes and ketones to electrophiles is a cornerstone reaction for the synthesis of unusual sugars and chiral building blocks. We investigated d-fructose-6-phosphate aldolase from E. coli (FSA) D6X variants as catalysts for the aldol additions of ethanal and nonfunctionalized linear and cyclic aliphatic ketones as nucleophiles to nonphosphorylated hydroxyaldehydes. Thus, addition of propanone, cyclobutanone, cyclopentanone, or ethanal to 3-hydroxypropanal or ( S )- or ( R )-3-hydroxybutanal catalyzed by FSA D6H and D6Q variants furnished rare deoxysugars in 8-77% isolated yields with high stereoselectivity (97:3 dr and >95% ee )., Competing Interests: The authors declare no competing financial interest.

This work describes the employment of discrete "AgCF 3 " complexes as efficient transmetalating agents to Pd II to surmount overlooked challenges related to the transmetalation step in Pd-catalyzed trifluoromethylation processes. We report the participation of a unique silver ate (Cs)[Ag(CF 3 ) 2 ] complex, under stoichiometric and catalytic conditions, in the unprecedented one-pot formation of PhCF 3 using PhI as starting material. Moreover, we show that the transmetalation step, which is often ignored in these transformations, can also determine the success or failure of the coupling process., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study aims to explore the biological functions of the isolated exopolysaccharides (EPSs) produced during the industrial fermentation of olives against enterotoxigenic E. coli (ETEC) K88. Exopolysaccharides were isolated from five industrial fermenters. Analysis of their monosaccharide composition by GLC revealed that the main components were glucose (27%-50%) and galactose (23%-33%) followed by rhamnose (4-23%) and arabinose (6-17%). The 1H NMR spectrum showed a very similar profile between samples, and a more in-depth analysis revealed the presence of an α-pyranose in the form of α-d-Glcp-(1→) and two different α-furanoses, with chemicals shift values, suggesting the presence of α-d-Glcf and α-d-Galf. Miniaturized in vitro tests demonstrated the ability of EPS samples to attach specifically to ETEC K88 (P < 0.05) with variable intensities. The competition test did not show the ability to block the ETEC K88 adhesion to IPEC-J2 cells; however, in the displacement test, all EPS samples were shown to effectively remove the pathogens attached to the cells (P < 0.01). These results suggest that the EPSs produced during the fermentation of table green olives could interfere with the attachment of opportunistic pathogens onto the intestinal epithelial cells. This would open the possibility of novel functional properties for this traditional Mediterranean fermented food and for the isolated EPSs as candidates for nutraceutics to be used in human and/or animal diets in the prevention and treatment of ETEC diarrhoea.

Modern resolution-enhanced NMR techniques can monitor the in situ discrimination of co-existing isotropic and anisotropic contributions of small molecules dissolved in weakly aligning PMMA/CDCl3 media. The simultaneous sign-sensitive determination of accurate Δδ iso-aniso ( 1 H), Δδ iso-aniso ( 13 C) and/or isotropic 1 J CH and anisotropic 1 T CH coupling constants (and consequently 1 H- 13 C residual dipolar couplings and 1 H/ 13 C residual chemical shift anisotropies) can be performed from spectral-aliased heteronuclear single-quantum correlation spectra., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The encapsulation of coordination complexes in a tetragonal prismatic nanocage (1·(BAr F ) 8 ) built from Zn-porphyrin and macrocyclic Pd-clip-based synthons is described. The functional duality of the guest ligand L 1 allows for its encapsulation inside the cage 1·(BAr F ) 8 , along with the simultaneous coordination of Zn II , Cu II , or Fe III metal ions. Remarkably, the coordination chemistry inside the host-guest adduct L 1 ⊂1·(BAr F ) 8 occurs in both solution solution and solid state. The resulting confined metallocomplexes have been characterized by means of UV-vis, ESI-HRMS, NMR, and EPR techniques. Furthermore, the emission of the Zn-porphyrin fluorophores of 1·(BAr F ) 8 is strongly quenched by the encapsulation of paramagnetic complexes, representing a remarkable example of guest-dependent tuning of the host fluorescence.

Two-dimensional J-resolved (Jres) NMR experiments offer a simple, user-friendly spectral representation where the information of coupling constants and chemical shifts are separated into two orthogonal frequency axis. Since its initial proposal 40 years ago, Jres has been the focus of considerable interest both in improving the basic pulse sequence and in its successful application to a wide range of studies. Here, the latest developments in the design of novel Jres pulse schemes are reviewed, mainly focusing on obtaining pure absorption lineshapes, minimizing strong coupling artifacts, and also optimizing sensitivity and experimental measurements. A discussion of several Jres versions for the accurate measurement of a different number of homonuclear (J HH ) and heteronuclear (J CH ) coupling constants is presented, accompanied by some illustrative examples., (Copyright © 2018 John Wiley & Sons, Ltd.)

Gold(iii) complexes are garnering increasing interest for opto-electronic, therapeutic and catalytic applications. But so far, very little is known about the factors controlling their reactivity and the very influence of the ancillary ligand. This article reports the first comprehensive study on this topic. The reactivity of a cationic (N,C) gold(iii) complex, namely 1A , towards ethylene has been thoroughly studied and compared with that of the related (P,C) complex 1C . A cationic gold(iii) complex 5A resulting from double insertion of ethylene was selectively obtained. Complex 5A was found to be remarkably stable. It was trapped with chloride and fully characterized. In marked contrast to that observed with 1C , no β-H elimination or linear-to-branched rearrangement of the alkyl chain occurred with 1A . The energy profile for the reactions of 1A with ethylene has been comprehensively investigated computationally, and the influence of the ancillary ligand has been precisely delineated. Because nitrogen is a weaker donor than carbon (and phosphorus), the (N,C) ligand is very electronically dissymmetric, much more than the (P,C) ligand. This makes the two reactive sites at gold quite different, which noticeably influences the competition between migratory insertion and β-H elimination, and actually changes the outcome of the olefin insertion at gold. This study provides valuable insight into the influence of ancillary ligands on gold(iii) reactivity, something critical to further develop Au(iii) and Au(i)/Au(iii) catalysis.

Pyruvate-dependent aldolases exhibit a stringent selectivity for pyruvate, limiting application of their synthetic potential, which is a drawback shared with other existing aldolases. Structure-guided rational protein engineering rendered a 2-keto-3-deoxy-l-rhamnonate aldolase variant, fused with a maltose-binding protein (MBP-YfaU W23V/L216A), capable of efficiently converting larger pyruvate analogues, for example, those with linear and branched aliphatic chains, in aldol addition reactions. Combination of these nucleophiles with N-Cbz-alaninal (Cbz=benzyloxycarbonyl) and N-Cbz-prolinal electrophiles gave access to chiral building blocks, for example, derivatives of (2S,3S,4R)-4-amino-3-hydroxy-2-methylpentanoic acid (68 %, d.r. 90:10) and the enantiomer of dolaproine (33 %, d.r. 94:6) as well as a collection of unprecedented α-amino acid derivatives of the proline and pyrrolizidine type. Conversions varied between 6-93 % and diastereomeric ratios from 50:50 to 95:5 depending on the nucleophilic and electrophilic components., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Allene-(E)-ene-yne N-tosyl-tethered substrates 3 a-3 h were efficiently prepared and their rhodium-catalyzed [2+2+2] cycloaddition reactions were evaluated. The cycloadditions are chemoselective as only the proximal double bond of the allene reacted to afford exocyclic double bonds in the fused-tricyclic scaffolds. The stereoselectivity depended on the catalytic system used. Reactivity between allene, alkene, and alkyne was studied for the first time by density functional theory calculations. This mechanistic study determines the order in which the unsaturated groups take part in the catalytic cycle., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein we describe the synthesis of a family of aryl-Co(III)-carboxylate complexes and their reactivity with ethyl diazoacetate. Crystallographic, full spectroscopic characterization, and theoretical evidence of unique C-metalated aryl-Co(III) enolate intermediates is provided, unraveling a carboxylate-assisted formation of aryl-Co(III) masked-carbenes. Moreover, additional evidence for an unprecedented Co(III)-mediated intramolecular S N 2-type C-C bond formation in which the carboxylate moiety acts as a relay is disclosed. This novel strategy is key to tame the hot reactivity of a metastable Co(III)-carbene and elicit C-C coupling products in a productive manner.

In this work, we describe the synthesis of a new N-heterocyclic carbene (NHC) ligand, derived from a hybrid pyrazole-imidazolium scaffold, namely 1-[2-(3,5-dimethylpyrazol-1-yl)ethyl]-3-((S)-1-phenylethyl)-3H-imidazol-2-ylidene (L). This ligand has been used as a stabilizer for the organometallic synthesis of palladium(0) nanoparticles (Pd NPs). L presents a better stabilizing effect than its pre-carbenic HLCl counterpart, allowing the formation of isolated Pd NPs while HLCl yields aggregated ones. Additionally, molecular Pd(ii) coordination compounds of L and HLCl were synthesized and characterized to better understand the coordination modes of these ligands. Both molecular and colloidal Pd systems have been further tested in catalytic C-C coupling processes. Three different types of reactions have been observed depending on the catalytic system: (i) the Suzuki-Miyaura reaction takes place with Pd molecular complexes; (ii) a secondary reaction, the dehalogenation of the substrate, is always detected and (iii) the C-C homocoupling between two molecules of bromoarenes is observed with colloidal catalysts.

The measurement of two-bond proton-proton coupling constants ( 2 J HH ) in prochiral CH 2 groups from the F2 dimension of 2D spectra is not easy due to the usual presence of complex multiplet J patterns, line broadening effects and strong coupling artifacts. These drawbacks are particularly pronounced and frequent in AB spin systems, as those normally exhibited by the pair of diastereotopic CH 2 protons. Here, a novel 2 J HH -resolved HSQC experiment for the exclusive and accurate determination of the magnitude of 2 J HH from the doublet displayed along the highly-resolved indirect F1 dimension is described. A pragmatic 2 J HH NMR profile affords a fast overview of the full range of existing 2 J HH values. In addition, a 2 J HH /δ( 13 C)-scaled version proves to be an efficient solution when severe signal overlapping complicate a rigorous analysis. The performance of the method is compared with other current techniques and illustrated by the determination of challenging residual dipolar 2 D HH coupling constants of small molecules dissolved in weakly orienting media., (Copyright © 2017 Elsevier Inc. All rights reserved.)

A number of J-upscaled NMR experiments are currently available to measure coupling constants along the indirect F1 dimension of a 2D spectrum. A major drawback is the limited F1 digital resolution that requires long acquisition times in order to achieve reasonably accurate measures. Here is shown how high levels of F1 digital resolution in a multiple-purpose HSQC experiment can be easily achieved by implementing a general J/δ-scaling strategy. In particular, a set of new J-resolved HSQC experiments is presented for a faster and much more accurate J determination in small molecules. Several options and practical aspects are discussed and exemplified by measuring the magnitude and/or the sign of several homo- and heteronuclear coupling constants in one shot., (Copyright © 2017 Elsevier Inc. All rights reserved.)

γ-Hydroxybutyric acid (GHB) is a popular drug increasingly associated with cases of drug-facilitated sexual assault (DFSA). Currently, expanding procedures of analysis and having forensic evidence of GHB intake in a long term are mandatory. Up to now, most studies have been performed using GC/MS and LC-MS as analytical platforms, which involve significant manipulation of the sample and, often, indirect measurements. In this work, procedures used in NMR-based metabolomics were applied to a GHB clinical trial on urine and serum. Detection, identification, and quantification of the drug by NMR methods were surveyed, as well as the use of NMR-based metabolomics for the search of potential surrogate biomarkers of GHB consumption. Results demonstrated the suitability of NMR spectroscopy, as a robust nondestructive technique, to fast and directly monitor (detect, identify, and quantify) exogenous GHB in almost intact body fluids and its high potential in the search for metabolites associated with GHB intake.

Selective refocusing (GSERF or the recent PSYCHEDELIC) experiments were originally designed to determine all proton-proton coupling constants (J HH ) for a selected proton resonance. They work for isolated signals on which selective excitation can be successfully applied but, as it happens in other selective experiments, fail for overlapped signals. To circumvent this limitation, a doubly-selective TOCSY-GSERF scheme is presented for the measurement of J HH in protons resonating in crowded regions. This new experiment takes advantage of the editing features of an initial TOCSY transfer to uncover hidden resonances that become accessible to perform the subsequent frequency-selective refocusing. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

A fast residual dipolar coupling constant-assisted strategy involving the simultaneous determination of scalar and total coupling constants from a single 1 J CH / 2 J HH -resolved NMR spectrum is reported. It is shown that the concerted use of the directly measured 1 D CH (for all CH n multiplicities) and 2 D HH residual dipolar couplings allows an on-the-fly assignment of diastereotopic CH 2 protons, as well as of an efficient discrimination between diastereoisomeric structures of strychnine which contains six stereocenters. Copyright © 2017 John Wiley & Sons, Ltd., (Copyright © 2017 John Wiley & Sons, Ltd.)

Background: Tropical rainforests are frequently limited by soil nutrient availability. However, the response of the metabolic phenotypic plasticity of trees to an increase of soil nutrient availabilities is poorly understood. We expected that increases in the ability of a nutrient that limits some plant processes should be detected by corresponding changes in plant metabolome profile related to such processes., Methodology/principal Findings: We studied the foliar metabolome of saplings of three abundant tree species in a 15 year field NPK fertilization experiment in a Panamanian rainforest. The largest differences were among species and explained 75% of overall metabolome variation. The saplings of the large canopy species, Tetragastris panamensis, had the lowest concentrations of all identified amino acids and the highest concentrations of most identified secondary compounds. The saplings of the "mid canopy" species, Alseis blackiana, had the highest concentrations of amino acids coming from the biosynthesis pathways of glycerate-3P, oxaloacetate and α-ketoglutarate, and the saplings of the low canopy species, Heisteria concinna, had the highest concentrations of amino acids coming from the pyruvate synthesis pathways., Conclusions/significance: The changes in metabolome provided strong evidence that different nutrients limit different species in different ways. With increasing P availability, the two canopy species shifted their metabolome towards larger investment in protection mechanisms, whereas with increasing N availability, the sub-canopy species increased its primary metabolism. The results highlighted the proportional distinct use of different nutrients by different species and the resulting different metabolome profiles in this high diversity community are consistent with the ecological niche theory.