Flat aromatic compounds containing a boron-nitrogen (BN) fragment have gained significant attention in the field of organic optoelectronics. Unsurprisingly, therefore, an increasing number of synthetic methodology groups have devoted efforts and creativity to developing new strategies for accessing diverse structures incorporating a B[double bond, length as m-dash]N unit, which is isosteric with the olefinic C[double bond, length as m-dash]C bond. In contrast, the potential of BN isosterism to expand the structural diversity of three-dimensional architectures based on sp3-hybridized atoms remains largely underexplored. In this study, we introduce a strategy to construct an alkane-type quaternary-quaternary Bsp3-Nsp3 molecular axis via double addition of a carbon-based nucleophile/electrophile pair to a readily accessible olefin-type B[double bond, length as m-dash]N moiety. The approach is showcased through the synthesis of a BN-[4.4.4]-propellane, in which the rapidly assembled tetrahydro-BN-naphthalene intermediate undergoes a polar double allylation of its B[double bond, length as m-dash]N bond. Despite the unfavorable trans preference in this addition step, efficient [4.4.4]-propellane formation was achieved through a tandem metathesis-based trans-to-cis isomerization and ring-closing reaction. The resulting BN-propellane exhibits a C3-symmetric helical arrangement in the solid state and shows fluxional behavior in the 1H NMR spectrum at room temperature due to a helicity flip, for which variable-temperature NMR measurements yielded an activation barrier (ΔG ‡) of approximately 14.6 kcal mol-1.

This book chapter covers relevant articles published in peer-reviewed journals in 2024 in the field of NMR spectroscopy of small molecules in solution. Articles that appeared in 2024 as accepted online versions but were not published until 2025 are not included. The chapter is structured into seven sections: NMR pulse sequence development, mixture analysis, quantitative NMR, structural determination in oriented media, chiral recognition, artificial intelligence methods and a final miscellaneous section where interesting articles that did not fit in any of the earlier topics were included. Readers should not expect a fully detailed review, nor a simple, summary listing of articles. Instead, the reader shall find the main goals and key points from the selected publications.

Abstract 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 31P profiles. We tested this hypothesis by performing a metabolomic analysis of the soils in two rainforests in French Guiana using 31P nuclear magnetic resonance (NMR). We analysed 31P 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 31P 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 31P NMR profiles, although less than the influence of the tree species. Multivariate analyses of soil 31P 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.

Previous research revealed that several seminal plasma (SP) metabolites are related to sperm functionality, fertility, and preservation. While it is understood that variations between species exist, whether the SP metabolome differs between donkeys and horses has not been previously investigated. The aim of this work, therefore, was to characterize and compare donkey and horse SP metabolites using nuclear magnetic resonance (NMR) spectroscopy, and relate them to sperm viability and motility. For this purpose, ejaculates from 18 different donkeys and 18 different horses were collected and separated into two aliquots: one for harvesting the SP by centrifugation and obtaining the metabolic profile through NMR, and the other for evaluating sperm viability and motility. Based on total motility and sperm viability, samples were classified as with good (GQ) or poor (PQ) quality. The metabolomic profile of donkey and horse SP revealed the presence of 28 metabolites, which coincided in the two species. Yet, differences between horses and donkeys were observed in the concentration of 18 of these 28 metabolites, as well as between ejaculates classified as GQ or PQ and in the relationship of metabolites with sperm motility and viability. These findings suggest that sperm from donkeys and horses differ in their metabolism and energetic requirements, and that the concentration of specific SP metabolites may be related to sperm functionality. Further research should shed light on the metabolic needs of donkey and horse sperm, and evaluate how the knowledge collected from the contribution of these metabolites can help improve semen preservation in the two species.

A cobalt complex bearing a κ -N 3 P 2 ligand is presented ( 1 + or Co I (L), where L is (1 E ,1′ E )-1,1′-(pyridine-2,6-diyl)bis( N -(3-(diphenylphosphanyl)propyl)ethan-1-imine). Complex 1 + is stable under air at oxidation state Co I thanks to the π-acceptor character of the phosphine groups. Electrochemical behavior of 1 + reveals a two-electron Co I /Co III oxidation process and an additional one-electron reduction, which leads to an enhancement in the current due to hydrogen evolution reaction (HER) at E onset =−1.6 V vs Fc/Fc + . In the presence of 1 equiv of bis(trifluoromethane)sulfonimide, 1 + forms the cobalt hydride derivative Co III (L)-H ( 2 2+ ), which has been fully characterized. Further addition of 1 equiv of CoCp* 2 (Cp* is pentamethylcyclopentadienyl) affords the reduced Co II (L)-H ( 2 + ) species, which rapidly forms hydrogen and regenerates the initial Co I (L) ( 1 + ). The spectroscopic characterization of catalytic intermediates together with DFT calculations support an unusual bimolecular homolytic mechanism in the catalytic HER with 1 + .

We describe short non-natural peptides that adopt α- and β-turn folds in solution and in the crystal. The peptides are constituted by a core of trans and cis stereoisomers of polyhydroxylated cyclohexane γ-amino acids, flanked by dimers of L-α-alanine, resulting in hybrid hexapeptides with an ααγγαα backbone. DFT calculations and spectroscopic analysis by NMR, CD and FT-IR in solution are consistent with structural changes upon deprotection of certain hydroxyl groups of the central polyhydroxylated γ-amino acids. X-ray diffraction analysis of a crystalline sample revealed a double α-/β-turn that was also identified by NMR spectroscopy in acetonitrile-d3 solution.

The synthesis, full characterization, photochemical properties, and cytotoxic activity toward cisplatin-resistant cancer cell lines of new semisquaraine-type Pt(II) complexes are presented. The synthesis of eight semisquaraine-type ligands has been carried out by means of an innovative, straightforward methodology. A thorough structural NMR and X-ray diffraction analysis of the new ligands and complexes has been done. Density functional theory calculations have allowed to assign the trans configuration of the platinum center. Through the structural modification of the ligands, it has been possible to synthesize some complexes, which have turned out to be photoactive at wavelengths that allow their activation in cell cultures and, importantly, two of them show remarkable solubility in biological media. Photodegradation processes have been studied in depth, including the structural identification of photoproducts, thus justifying the changes observed after irradiation. From biological assessment, complexes C7 and C8 have been demonstrated to behave as promising photoactivatable compounds in the assayed cancer cell lines. Upon photoactivation, both complexes are capable of inducing a higher cytotoxic effect on the tested cells compared with nonphotoactivated compounds. Among the observed results, it is remarkable to note that C7 showed a PI > 50 in HeLa cells, and C8 showed a PI > 40 in A2780 cells, being also effective over cisplatin-resistant A2780cis cells (PI = 7 and PI = 4, respectively). The mechanism of action of these complexes has been studied, revealing that these photoactivated platinum complexes would actually present a combined mode of action, a therapeutically potential advantage.

Follicular fluid is formed from the transudation of theca and granulosa cells in the growing follicular antrum. Its main function is to provide an optimal intrafollicular microenvironment to modulate oocyte maturation. The aim of this study was to determine the metabolomic profile of preovulatory follicular fluid (PFF) in jennies. For this purpose, PFF was collected from 10 follicles of five jennies in heat. Then, PFF samples were analysed by nuclear magnetic resonance (NMR) and heteronuclear single quantum correlation (2D 1H/13C HSQC). Our study revealed the presence of at least 27 metabolites in the PFF of jennies (including common amino acids, carboxylic acids, amino acid derivatives, alcohols, saccharides, fatty acids, and lactams): 3-hydroxybutyrate, acetate, alanine, betaine, citrate, creatine, creatine phosphate, creatinine, ethanol, formate, glucose, glutamine, glycerol, glycine, hippurate, isoleucine, lactate, leucine, lysine, methanol, phenylalanine, proline, pyruvate, threonine, tyrosine, valine, and τ-methylhistidine. The metabolites found here have an important role in the oocyte development and maturation, since the PFF surrounds the follicle and provides it with the needed nutrients. Our results indicate a unique metabolic profile of the jennies PFF, as it differs from those previously observed in the PFF of the mare, a phylogenetically close species that is taken as a reference for establishing reproductive biotechnology techniques in donkeys. The metabolites found here also differ from those described in the TCM-199 medium enriched with fetal bovine serum (FBS), which is the most used medium for in vitro oocyte maturation in equids. These differences would suggest that the established conditions for in vitro maturation used so far may not be suitable for donkeys. By providing the metabolic composition of jenny PFF, this study could help understand the physiology of oocyte maturation as a first step to establish in vitro reproductive techniques in this species.

Weaning is a critical period in the life of pigs with repercussions on their health and welfare and on the economy of the swine industry. This study aimed to assess the effect of the commercial early weaning on gut microbiota, intestinal gene expression and serum metabolomic response via an integrated-omic approach combining 16S rRNA gene sequencing, the OpenArray gene expression technology and 1 H-NMR spectroscopy. Fourteen piglets from different litters were sampled for blood, jejunum tissue and caecal content two days before (− 2d), and three days after (+ 3d) weaning. A clearly differential ordination of caecal microbiota was observed. Higher abundances of Roseburia , Ruminococcus , Coprococcus , Dorea and Lachnospira genera in weaned piglets compared to prior to weaning showed the quick microbial changes of the piglets’ gut microbiota. Downregulation of OCLN , CLDN4 , MUC2 , MUC13 , SLC15A1 and SLC13A1 genes, also evidenced the negative impact of weaning on gut barrier and digestive functions. Metabolomic approach pinpointed significant decreases in choline, LDL, triglycerides, fatty acids, alanine and isoleucine and increases in 3-hydroxybutyrate after weaning. Moreover, the correlation between microbiota and metabolome datasets revealed the existence of metabolic clusters interrelated to different bacterial clusters. Our results demonstrate the impact of weaning stress on the piglet and give insights regarding the associations between gut microbiota and the animal gene activity and metabolic response.

The aim of this study was to determine the possible impact of early socialization and an enriched neonatal environment to improve adaptation of piglets to weaning. We hypothesized that changes in the microbiota colonization process and in their metabolic response and intestinal functionality could help the animals face weaning stress. A total of 48 sows and their litters were allotted into a control (CTR) or an enriched treatment (ENR), in which piglets from two adjacent pens were combined and enriched with toys. The pattern of caecal microbial colonization, the jejunal gene expression, the serum metabolome and the intestinal physiology of the piglets were assessed before (-2 d) and after weaning (+ 3d). A differential ordination of caecal microbiota was observed after weaning. Serum metabolome suggested a reduced energetic metabolism in ENR animals, as evidenced by shifts in triglycerides and fatty acids, VLDL/LDL and creatine regions. The TLR2 gene showed to be downregulated in the jejunum of ENR pigs after weaning. The integration of gene expression, metabolome and microbiota datasets confirmed that differences between barren and enriched neonatal environments were evident only after weaning. Our results suggest that improvements in adaptation to weaning could be mediated by a better response to the post-weaning stress.

Background:Metabolomic approaches, which include the study of low molecular weight molecules, are an emerging-omics technology useful for identification of biomarkers. In this field, nuclear magnetic resonance (NMR) spectroscopy has already been used to uncover (in) fertility biomarkers in the seminal plasma (SP) of several mammalian species. However, NMR studies profiling the porcine SP metabolome to uncover in vivo fertility biomarkers are yet to be carried out. Thus, this study aimed to evaluate the putative relationship between SP- metabolites and in vivo fertility outcomes. To this end, 24 entire ejaculates (three ejaculates per boar) were collected from artificial insemination (AI)-boars throughout a year (one ejaculate every 4 months). Immediately after collection, ejaculates were centrifuged to obtain SP-samples, which were stored for subsequent metabolomic analysis by NMR spectroscopy. Fertility outcomes from 1525 inseminations were recorded over a year, including farrowing rate, litter size, stillbirths per litter and the duration of pregnancy. Results:A total of 24 metabolites were identified and quantified in all SP-samples. Receiver operating characteristic (ROC) curve analysis showed that lactate levels in SP had discriminative capacity for farrowing rate (area under the curve [AUC]=0.764) while carnitine (AUC=0.847), hypotaurine (AUC=0.819), sn-glycero-3-phosphocholine (AUC=0.833), glutamate (AUC=0.799) and glucose (AUC=0.750) showed it for litter size. Similarly, citrate (AUC=0.743), creatine (AUC=0.812), phenylalanine (AUC=0.750), tyrosine (AUC=0.753) and malonate (AUC=0.868) levels had discriminative capacity for stillbirths per litter;and malonate (AUC=0.767) and fumarate (AUC=0.868) levels for gestation length. Conclusions:The assessment of selected SP-metabolites in ejaculates through NMR spectroscopy could be considered as a promising non-invasive tool to predict in vivo fertility outcomes in pigs. Moreover, supplementing AI-doses with specific metabolites should also be envisaged as a way to improve their fertility potential.

Heteronuclear long‐range scalar coupling constants (nJCH) 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 1H frequency selective HSQMBC experiments for the easy and accurate measurement of either the magnitude or both the magnitude and the sign of long‐range nJCH couplings. The performance of these experiments will be showcased with several scenarios in a range of different experimental conditions.

The detection of ultra-long-range (4JCH 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 nJCH 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.

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.

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.

•Dual interleaved acquisition of spectral-optimized HSQC datasets.•Simultaneous recording of conventional and aliased HSQC spectra.•A time-efficient strategy to obtain resolution-enhanced HSQC data.•Fast determination of accurate 13C chemical shifts from HSQC data.•Separate acquisition of equivalent coherence transfer pathways within the same scan.

Contamination of water with steroid residues can cause a number of environmental damages, affecting exposed organisms including man. The development of technologies for treatment or removal of this type of micro-pollutant from water is of paramount importance. In this study, citric acid was used to functionalize beta-Cyclodextrin (bCD) on the silica surface generating an organic-inorganic hybrid composite for application in molecular sequestration. The functionalization percentage was high, with about 62.6% of the composite mass corresponding to the organic part of the material. C-13 NMR and infrared spectroscopic analysis indicate that the functionalization mechanism occurs by an esterification reaction between the citric acid with the silanol groups from silica and the primary hydroxyls of the bCDs. Fast adsorption of the methyltestosterone steroid was observed at acid pH, with a high adsorption capacity of 11 mg g(-1). The best kinetic and isotherm models fit indicated that the adsorption occurred by a physical mechanism at independent sites with the steroid molecule possibly captured by two bCDs. The removal process was spontaneous and exothermic, with the existence of weak interactions between the hormone and the composite, and its regeneration is quite fast efficient with the displacement of the complexation equilibrium. The results obtained in this study demonstrate the considerable potential of the composite for use in the treatment of wastewater containing the steroid studied, and its efficacy should be evaluated for other steroid molecules.

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 1H‐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.

The concepts of pure-shift NMR and time-shared NMR are merged in a single experiment. A 13C/15N time-shared version of the real-time BIRD-based broadband homodecoupled HSQC experiment is described. This time-efficient approach affords simultaneously 1H-13C and 1H-15N pure-shift HSQC spectra in a single acquisition, while achieving substantial gains in both sensitivity and spectral resolution. We also present a related 13C/15N-F2-coupled homodecoupled version of the CLIP-HSQC experiment for the simultaneous measurement of 1JCH and 1JNH 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 1JCH/1JNH from a 2D J-resolved spectrum.