Search

A comparative study of Michael acceptor and keto-Michael acceptor inhibitors of the cysteine protease rhodesain has been performed. Five new inhibitors have been prepared bearing the peptide structure of the known cysteine protease inhibitor K11777 and differing on the warhead. For the preparation of the Michael acceptor warhead, a Horner-Wadsworth-Emmons reaction was used. In the synthetic routes of the keto-Michael acceptor warheads, keto-enoate and keto-vinyl sulfone, a metathesis reaction and a radical sulfonylation were the key steps, respectively. Interestingly, keto-Michael acceptors inhibited rhodesain through a dual mode of action, showing reversibility at low inhibitor concentrations and irreversibility at high inhibitor concentrations., Competing Interests: Declaration of competing interest The authors 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 Inc. All rights reserved.)

A new activity-based probe (ABP) of cysteine proteases (FGA139) has been designed and synthesized. The design of the ABP has been done based upon the chemical structure of an irreversible inhibitor of cysteine proteases by attaching a bodipy fluorophore at the N-terminus of the peptide backbone. The synthetic route of the probe has a metathesis and a "click" reaction as key steps. Although some studies have been reported about the role played by cysteine proteases in neurodegenerative diseases, there are not definitive conclusions. The obtained ABP has been employed as a chemical tool to profile activities of cysteine proteases cathepsins B, L, and calpain in neurodegenerative cell models through confocal imaging. Colocalization of the probe to specific antibodies of the proteases and competitive experiments with non-fluorescent inhibitors confirm the specificity of the ABP. From a theranostic perspective, our findings strongly suggest that FGA139 exhibits a protective role in various cell lines against oxidative stress or pro-inflammatory toxicity and it effectively attenuates macrophage activation triggered by LPS., (© 2024 The Authors. ChemMedChem published by Wiley-VCH GmbH.)

Flowers, and hence, fruits and seeds, are produced by the activity of the inflorescence meristem after the floral transition. In plants with indeterminate inflorescences, the final number of flowers produced by the inflorescence meristem is determined by the length of the flowering period, which ends with inflorescence arrest. Inflorescence arrest depends on many different factors, such as the presence of seeds, the influence of the environment, or endogenous factors such as phytohormone levels and age, which modulate inflorescence meristem activity. The FRUITFULL-APETALA2 (FUL-AP2) pathway plays a major role in regulating the end of flowering, likely integrating both endogenous cues and those related to seed formation. Among AP2 targets, HOMEOBOX PROTEIN21 (HB21) has been identified as a putative mediator of AP2 function in the control of inflorescence arrest. HB21 is a homeodomain leucine zipper transcription factor involved in establishing axillary bud dormancy. Here, we characterized the role of HB21 in the control of the inflorescence arrest at the end of flowering in Arabidopsis (Arabidopsis thaliana). HB21, together with HB40 and HB53, are upregulated in the inflorescence apex at the end of flowering, promoting floral bud arrest. We also show that abscisic acid (ABA) accumulation occurs in the inflorescence apex in an HB-dependent manner. Our work suggests a physiological role of ABA in floral bud arrest at the end of flowering, pointing to ABA as a regulator of inflorescence arrest downstream of the HB21/40/53 genes., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Glycans decorate all cells and are critical mediators of cellular processes through recognition by glycan-binding proteins (GBPs). While targeting glycan-protein interactions has great therapeutic potential, these interactions are challenging to study as they are generally transient and exhibit low binding affinities. Glycan-based photo-crosslinkable probes have enabled covalent capture and identification of unknown GBP receptors and glycoconjugate ligands. Here, we review recent progress in photo-crosslinking approaches targeting glycan-mediated interactions. We discuss two prominent emerging strategies: 1) development of photo-crosslinkable oligosaccharide ligands to identify GBP receptors; and 2) cell-surface glyco-engineering to identify glycoconjugate ligands of GBPs. Overall, photoaffinity labeling affords valuable insights into complex glycan-protein networks and is poised to help elucidate the glycan-protein interactome, providing novel targets for therapeutic intervention., Competing Interests: Declaration of competing interest The authors 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 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: The aim of this study was to evaluate the impact of an enhanced ONS (enriched in EPA, DHA, leucine, and beta-glucans) on the dietary intake of cancer patients., Methods: A randomized, double-blind, parallel, controlled, and multicenter clinical trial was conducted in patients with cancer and malnutrition. The trial compared prescribed dietary advice and two packs per day, for 8 weeks, of a hypercaloric (400 kcal/pack) and hyperproteic ONS (20 g/pack) with fiber and specific ingredients (leucine, EPA and DHA, and beta-glucans) (enhanced-ONS) versus an isocaloric and isoproteic formula (standard-ONS) without specific ingredients. Food intake was assessed with a 3-day dietary survey, and adherence to the supplement with a patient self-completed diary., Results: Thirty-seven patients completed the intervention period. The combined intervention of dietary advice and ONS managed to increase the energy intake of the overall cohort by 792.55 (378.57) kcal/day, protein by 40.72 (19.56) g/day. Increases in energy and nutrient intakes were observed in both groups, both in dietary intake and associated exclusively with the supplement. The group that received the enhanced-ONS ingested a greater volume of product when there was a greater severity of malnutrition; a tumor location in the head, neck, upper digestive area, liver, or pancreas; more advanced stages of the tumor; or the receipt of more than one antineoplastic treatment., Conclusion: The use of an enhanced-ONS helps meet the nutritional requirements of cancer patients, especially those who have a more compromised clinical condition, with high adherence, good tolerance, and acceptance., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Samara Palma Milla reports financial support was provided by Centro para el Desarrollo Tecnológico Industrial from the Ministerio de Economía y Competitividad (Government of Spain), Exp. IDI 20170916. Alicia Calleja Fernandez reports a relationship with Adventia Pharma that includes: employment. Tamara Casanas Quintana reports a relationship with Adventia Pharma that includes: employment., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Exo-enzymatic glyco-engineering of cell-surface glycoconjugates enables the selective display of well-defined glyco-motifs bearing bioorthogonal functional groups, which can be used to study glycans and their interactions with glycan-binding proteins. In recent years, strategies to edit cellular glycans by installing monosaccharides and their derivatives using glycosyltransferase enzymes have rapidly expanded. However, analogous methods to introduce chemical reporter-functionalized type 2 LacNAc motifs have not been reported. Herein, we report the chemo-enzymatic synthesis of unnatural UDP-GlcNAc and UDP-GalNAc nucleotide-sugars bearing azide, alkyne, and diazirine functionalities on the C2-acetamido group using the mutant uridylyltransferase AGX1 F383A . The unnatural UDP-GlcNAc derivatives were examined as substrates for the human GlcNAc-transferase B3GNT2, where it was found that modified donors were tolerated for transfer, albeit to a lesser extent than the natural UDP-GlcNAc substrate. When the GlcNAc derivatives were examined as acceptor substrates for the human Gal-transferase B4GalT1, all derivatives were well tolerated and the enzyme could successfully form derivatized LacNAcs. B3GNT2 was also used to exo-enzymatically install GlcNAc and unnatural GlcNAc derivatives on cell-surface glycans. GlcNAc- or GlcNAz-engineered cells were further extended by B4GalT1 and UDP-Gal, producing LacNAc- or LacNAz-engineered cells. Our proof-of-concept glyco-engineering labeling strategy is amenable to different cell types and our work expands the exo-enzymatic glycan editing toolbox to selectively introduce unnatural type 2 LacNAc motifs.

The coronavirus disease 2019 (COVID-19) pandemic continues to represent a global public health issue. The viral main protease (M pro ) represents one of the most attractive targets for the development of antiviral drugs. Herein we report peptidyl nitroalkenes exhibiting enzyme inhibitory activity against M pro (K i : 1-10 μM) good anti-SARS-CoV-2 infection activity in the low micromolar range (EC 50 : 1-12 μM) without significant toxicity. Additional kinetic studies of compounds FGA145, FGA146 and FGA147 show that all three compounds inhibit cathepsin L, denoting a possible multitarget effect of these compounds in the antiviral activity. Structural analysis shows the binding mode of FGA146 and FGA147 to the active site of the protein. Furthermore, our results illustrate that peptidyl nitroalkenes are effective covalent reversible inhibitors of the M pro and cathepsin L, and that inhibitors FGA145, FGA146 and FGA147 prevent infection against SARS-CoV-2., (© 2024. The Author(s).)

All cells are decorated with complex carbohydrate structures called glycans that serve as ligands for glycan-binding proteins (GBPs) to mediate a wide range of biological processes. Understanding the specific functions of glycans is key to advancing an understanding of human health and disease. However, the lack of convenient and accessible tools to study glycan-based interactions has been a defining challenge in glycobiology. Thus, the development of chemical and biochemical strategies to address these limitations has been a rapidly growing area of research. In this review, we describe the use of glycosyltransferases (GTs) as versatile tools to facilitate a greater understanding of the biological roles of glycans. We highlight key examples of how GTs have streamlined the preparation of well-defined complex glycan structures through chemoenzymatic synthesis, with an emphasis on synthetic strategies allowing for site- and branch-specific display of glyco-epitopes. We also describe how GTs have facilitated expansion of glyco-engineering strategies, on both glycoproteins and cell surfaces. Coupled with advancements in bioorthogonal chemistry, GTs have enabled selective glyco-epitope editing of glycoproteins and cells, selective glycan subclass labeling, and the introduction of novel biomolecule functionalities onto cells, including defined oligosaccharides, antibodies, and other proteins. Collectively, these approaches have contributed great insight into the fundamental biological roles of glycans and are enabling their application in drug development and cellular therapies, leaving the field poised for rapid expansion., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Cathepsin L (CatL) is a lysosomal cysteine protease whose activity has been related to several human pathologies. However, although preclinical trials using CatL inhibitors were promising, clinical trials have been unsuccessful up to now. We are presenting a study of two designed dipeptidyl keto Michael acceptor potential inhibitors of CatL with either a keto vinyl ester or a keto vinyl sulfone (KVS) warhead. The compounds were synthesized and experimentally assayed in vitro , and their inhibition molecular mechanism was explored based on molecular dynamics simulations at the density functional theory/molecular mechanics level. The results confirm that both compounds inhibit CatL in the nanomolar range and show a time-dependent inhibition. Interestingly, despite both presenting almost equivalent equilibrium constants for the reversible formation of the noncovalent enzyme/inhibitor complex, differences are observed in the chemical step corresponding to the enzyme-inhibitor covalent bond formation, results that are mirrored by the computer simulations. Theoretically determined kinetic and thermodynamic results, which are in very good agreement with the experiments, afford a detailed explanation of the relevance of the different structural features of both compounds having a significant impact on enzyme inhibition. The unprecedented binding interactions of both inhibitors in the P1' site of CatL represent valuable information for the design of inhibitors. In particular, the peptidyl KVS can be used as a starting lead compound in the development of drugs with medical applications for the treatment of cancerous pathologies since sulfone warheads have previously shown promising cell stability compared to other functions such as carboxylic esters. Future improvements can be guided by the atomistic description of the enzyme-inhibitor interactions established along the inhibition reaction derived from computer simulations., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Cysteine proteases (CPs) are an important class of enzymes, many of which are responsible for several human diseases. For instance, cruzain of protozoan parasite Trypanosoma cruzi is responsible for the Chagas disease, while the role of human cathepsin L is associated with some cancers or is a potential target for the treatment of COVID-19. However, despite paramount work carried out during the past years, the compounds that have been proposed so far show limited inhibitory action against these enzymes. We present a study of proposed covalent inhibitors of these two CPs, cruzain and cathepsin L, based on the design, synthesis, kinetic measurements, and QM/MM computational simulations on dipeptidyl nitroalkene compounds. The experimentally determined inhibition data, together with the analysis and the predicted inhibition constants derived from the free energy landscape of the full inhibition process, allowed describing the impact of the recognition part of these compounds and, in particular, the modifications on the P2 site. The designed compounds and, in particular, the one with a bulky group (Trp) at the P2 site show promising in vitro inhibition activities against cruzain and cathepsin L for use as a starting lead compound in the development of drugs with medical applications for the treatment of human diseases and future designs., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Since the outbreak of COVID-19, one of the strategies used to search for new drugs has been to find inhibitors of the main protease (Mpro) of the virus SARS-CoV-2. Initially, previously reported inhibitors of related proteases such as the main proteases of SARS-CoV and MERS-CoV were tested. A huge effort was then carried out by the scientific community to design, synthesize and test new small molecules acting as inactivators of SARS-CoV-2 Mpro. From the chemical structure view, these compounds can be classified into two main groups: one corresponds to modified peptides displaying an adequate sequence for high affinity and a reactive warhead; and the second is a diverse group including chemical compounds that do not have a peptide framework. Although a drug including a SARS-CoV-2 main protease inhibitor has already been commercialized, denoting the importance of this field, more compounds have been demonstrated to be promising potent inhibitors as potential antiviral drugs.

A computational study of the two possible inhibition mechanisms of rhodesain cysteine protease by the dipeptidyl enoate Cbz-Phe-Leu-CH=CH-CO 2 C 2 H 5 has been carried out by means of molecular dynamics simulations with hybrid QM/MM potentials. The low free energy barriers confirm that the Cys25 residue can attack both C β and C1 atoms of the inhibitor, confirming a dual mode of action in the inhibition of the rhodesain by enoates. According to the results, the inhibition process through the Cys25 attack on the C β atom of the inhibitor is an exergonic and irreversible process, while the inhibition process when Cys25 attacks on the C1 atom of the inhibitor is and exergonic but reversible process. The interactions between the inhibitor and rhodesain suggest that P2 is the most important fragment to consider in the design of new efficient inhibitors of rhodesain. These results may be useful for the design of new inhibitors of rhodesain and other related cysteine proteases based on dipeptidyl enoates scaffolds., (© 2021 Wiley-VCH GmbH.)

The SARS-CoV-2 main protease (M pro ) is essential for replication of the virus responsible for the COVID-19 pandemic, and one of the main targets for drug design. Here, we simulate the inhibition process of SARS-CoV-2 M pro with a known Michael acceptor (peptidyl) inhibitor, N3 . The free energy landscape for the mechanism of the formation of the covalent enzyme-inhibitor product is computed with QM/MM molecular dynamics methods. The simulations show a two-step mechanism, and give structures and calculated barriers in good agreement with experiment. Using these results and information from our previous investigation on the proteolysis reaction of SARS-CoV-2 M pro , we design two new, synthetically accessible N3 -analogues as potential inhibitors, in which the recognition and warhead motifs are modified. QM/MM modelling of the mechanism of inhibition of M pro by these novel compounds indicates that both may be promising candidates as drug leads against COVID-19, one as an irreversible inhibitor and one as a potential reversible inhibitor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this work a computational study of the mechanism of inhibition of cruzain, rhodesain, and cathepsin L cysteine proteases by the dipeptidyl nitroalkene Cbz-Phe-Ala-CH=CH-NO 2 has been carried out by means of molecular dynamics simulations with hybrid QM/MM potentials. The free-energy surfaces confirmed that the inhibition takes place by the formation of a covalent bond between the protein and the β-carbon atom of the inhibitor. According to the results, the tested inhibitor should be a much more efficient inhibitor of cruzain than of rhodesain, and little activity would be expected against cathepsin L, in total correspondence with the available experimental data. The origin of these differences may lie in the different stabilizing electrostatic interactions established between the inhibitor and the residues of the active site and S2 pocket of these enzymes. These results may be useful for the rational design of new dipeptidyl nitroalkenes with higher and more selective inhibitory activity against cysteine proteases., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on the regio- and stereoselective synthesis of tetrahydrofurans by reaction between epoxides and alkenes in the presence of a Lewis acid. This is an unprecedented formal [3+2] cycloaddition reaction between an epoxide and an alkene. The chemical reaction represents a very concise synthesis of tetrahydrofurans from accessible starting compounds.

Aldehydes are easily transformed into vicinal diamines and piperazines through a one-pot procedure including a Darzens reaction and treatment with an amine or diamine and then with a reducing agent. Additionally, quinoxalines can be accessed by reaction with 1,2-benzenediamine under oxidative conditions. These transformations are simple methods for the preparation of synthetically interesting monosubstituted diamines, piperazines, and quinoxalines., Competing Interests: The authors declare no competing financial interest.

A family of dipeptidyl enoates has been prepared and tested against the parasitic cysteine proteases rhodesain, cruzain and falcipain-2 related to sleeping sickness, Chagas disease and malaria, respectively. They have also been tested against human cathepsins B and L1 for selectivity. Dipeptidyl enoates resulted to be irreversible inhibitors of these enzymes. Some of the members of the family are very potent inhibitors of parasitic cysteine proteases displaying k 2nd (M -1 s -1 ) values of seven orders of magnitude. In vivo antiprotozoal testing was also performed. Inhibitors exhibited IC 50 values in the micromolar range against Plasmodium falciparum, Trypanosoma brucei, Trypanosoma cruzi and even more promising lower values against Leishmania donovanii., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Nitroepoxides are easily transformed into benzodiazepines, tetrahydrobenzodiazepines, imidazopyridines, and N-alkyl tetrahydroquinoxalines by treatment with 2-aminobenzylamines, 2-aminopyridines, and N-alkyl 1,2-diaminobenzenes, respectively. Regioselectivity is controlled through attack of the most nucleophilic nitrogen of the unsymmetrical diamine to the β position of the epoxide. These reactions represent an efficient way to prepare privileged bioactive structures.

Cysteine proteases are the most abundant proteases in parasitic protozoa and they are essential enzymes to the life cycle of several of them, thus becoming attractive therapeutic targets for the development of new inhibitors. In this paper, a computational study of the inhibition mechanism of cysteine protease by dipeptidyl-2,3-epoxyketone Cbz-Phe-Hph-(S), a recently proposed inhibitor, has been carried out by means of molecular dynamics (MD) simulations with hybrid QM/MM potentials. The computed free energy surfaces of the inhibition mechanism of cysteine proteases by peptidyl epoxyketones showing how the activation of the epoxide ring and the attack of Cys25 on either C2 or C3 atoms take place in a concerted manner. According to our results, the acid species responsible for the protonation of the oxygen atom of the ring would be able to conserve His159, in contrast to previous studies that proposed a water molecule as the activating species. The low activation free energies for the reaction where Cys25 attacks the C2 atom of the epoxide ring (12.1 kcal mol -1 ) or to the C3 atom (15.4 kcal mol -1 ), together with the high negative reaction energies suggest that the derivatives of peptidyl-2,3-epoxyketones can be used to develop new potent inhibitors for the treatment of Chagas disease.

Dipeptidyl nitroalkenes are potent reversible inhibitors of cysteine proteases. Inhibitor 11 resulted to be the most potent one with K i values of 0.49 and 0.44 nM against rhodesain and cruzain, respectively. According to enzymatic dilution and dialysis experiments, as well as computational and NMR studies, dipeptidyl nitroalkenes are tightly binding covalent reversible inhibitors.

Nitroepoxides are potentially exploitable as synthons with vicinal electrophilic centers. Nevertheless, although advances have been made in the field, enantioselective epoxidation of nitroalkenes is still a challenging process. Herein we show a convenient procedure for the preparation of optically active nitroepoxides in high enantiomeric excess and high chemical yield. The kinetic data of the best catalyst have been examined using computational methods based on DFT calculations. Interestingly, the results demonstrate that the enantioselectivity of the epoxidation of nitroalkenes by this kind of catalyst is not only kinetically but also thermodynamically controlled.

Dipeptidyl enoates were prepared through a high-yielding two-step synthetic route. They have a dipeptidic structure with a 4-oxoenoate moiety as a warhead with multiple reactive sites. Dipeptidyl enoates were screened against rhodesain and human cathepsins B and L, and were found to be potent and selective inhibitors of rhodesain. Among them (S,E)-ethyl 5-((S)-2-{[(benzyloxy)carbonyl]amino}-3-phenylpropanamido)-7-methyl-4-oxooct-2-enoate (6) was the most potent, with an IC50 value of 16.4 nM and kinact /Ki =1.6×10(6)  M(-1)  s(-1) against rhodesain. These dipeptidyl enoates display a reversible mode of inhibition at very low concentrations and an irreversible mode at higher concentrations. Inhibition kinetics data, supported by docking studies, suggest a dual mode of action via attack of cysteine thiolate at two reactive positions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A Darzens reaction between tert-butoxycarbonyl alaninal and chloromethyl phenyl sulfone afforded chlorohydrins, which were converted into epoxysulfones by reaction with sodium tert-butoxide. Epoxysulfone 10 and chloroketone 14 derived from chlorohydrins by oxidation proved to be inhibitors of cathepsins H, S, and C as determined by competitive activity-based protein profiling.

The MAPK (mitogen-activated protein kinase) p38 is an important mediator of inflammation and of inflammatory and neuropathic pain. We have described recently that docking-groove-dependent interactions are important for p38 MAPK-mediated signal transduction. Thus virtual screening was performed to identify putative docking-groove-targeted p38 MAPK inhibitors. Several compounds of the benzo-oxadiazol family were identified with low micromolar inhibitory activity both in a p38 MAPK activity assay, and in THP-1 human monocytes acting as inhibitors of LPS (lipopolysaccharide)-induced TNFα (tumour necrosis factor α) secretion. Positions 2 and 5 in the phenyl ring are essential for the described inhibitory activity with a chloride in position 5 and a methyl group in position 2 yielding the best results, giving an IC₅₀ value of 1.8 μM (FGA-19 compound). Notably, FGA-19 exerted a potent and long-lasting analgesic effect in vivo when tested in a mouse model of inflammatory hyperalgesia. A single intrathecal injection of FGA-19 completely resolved hyperalgesia, being 10-fold as potent and displaying longer lasting effects than the established p38 MAPK inhibitor SB239063. FGA-19 also reversed persistent pain in a model of post-inflammatory hyperalgesia in LysM (lysozyme M)-GRK2 (G-protein-coupled-receptor kinase)(+/-) mice. These potent in vivo effects suggested p38 MAPK docking-site-targeted inhibitors as a potential novel strategy for the treatment of inflammatory pain.

Nitroepoxides are easily transformed into 1,4-diamino heterocycles such as quinoxalines and pyrazines by treatment with 1,2-benzenediamines and ammonia, respectively. Additionally, related saturated heterocycles, such as piperazines and tetrahydroquinoxalines, can be accessed by treatment with 1,2-diamines and a reducing agent. These transformations are efficient, provide access privileged, bioactive structures, and produce minimal waste.

We present here a new measurement method for the rapid extraction and accurate quantification of technical nonylphenol (NP) and 4-t-octylphenol (OP) in complex matrix water samples by UHPLC-ESI-MS/MS. The extraction of both compounds is achieved in 30min by means of hollow fiber liquid phase microextraction (HF-LPME) using 1-octanol as acceptor phase, which provides an enrichment (preconcentration) factor of 800. On the other hand we have developed a quantification method based on isotope dilution mass spectrometry (IDMS) and singly (13)C1-labeled compounds. To this end the minimal labeled (13)C1-4-(3,6-dimethyl-3-heptyl)-phenol and (13)C1-t-octylphenol isomers were synthesized, which coelute with the natural compounds and allows the compensation of the matrix effect. The quantification was carried out by using isotope pattern deconvolution (IPD), which permits to obtain the concentration of both compounds without the need to build any calibration graph, reducing the total analysis time. The combination of both extraction and determination techniques have allowed to validate for the first time a HF-LPME methodology at the required levels by legislation achieving limits of quantification of 0.1ngmL(-1) and recoveries within 97-109%. Due to the low cost of HF-LPME and total time consumption, this methodology is ready for implementation in routine analytical laboratories., (Copyright © 2013 Elsevier B.V. All rights reserved.)

In this work we have developed and validated an accurate and fast methodology for the determination of 4-nonylphenol (technical mixture) in complex matrix water samples by UHPLC-ESI-MS/MS. The procedure is based on isotope dilution mass spectrometry (IDMS) in combination with isotope pattern deconvolution (IPD), which provides the concentration of the analyte directly from the spiked sample without requiring any methodological calibration graph. To avoid any possible isotopic effect during the analytical procedure the in-house synthesized (13)C1-4-(3,6-dimethyl-3-heptyl)phenol was used as labeled compound. This proposed surrogate was able to compensate the matrix effect even from wastewater samples. A SPE pre-concentration step together with exhaustive efforts to avoid contamination were included to reach the signal-to-noise ratio necessary to detect the endogenous concentrations present in environmental samples. Calculations were performed acquiring only three transitions, achieving limits of detection lower than 100ng/g for all water matrix assayed. Recoveries within 83-108% and coefficients of variation ranging from 1.5% to 9% were obtained. On the contrary a considerable overestimation was obtained with the most usual classical calibration procedure using 4-n-nonylphenol as internal standard, demonstrating the suitability of the minimal labeling approach., (Copyright © 2013 Elsevier B.V. All rights reserved.)

We report a highly diastereoselective synthesis of vicinal diamines by the treatment of nitroepoxides with primary amines and then a reducing agent. When using a chiral primary amine, racemic nitroepoxides are transformed into chiral diamines as a single enantiomers (>95:5 er) through a dynamic kinetic asymmetric transformation (DYKAT). The overall process is a one-pot procedure combining the exposure of nitroepoxides to chiral amines to afford diastereomeric mixtures of aminoimines and subsequent stereoselective imine reduction.

The mechanism of the dehydrosulfenylation of 2-arylsulfinyl esters was investigated. The reaction was found to follow a homolytic cleavage mechanism as verified by electrospray ionization tandem mass spectrometry and experimental work. Rearranged sulfoxides are obtained as byproduct during the elimination reaction.

Efficient ring opening of 3,4-epoxyesters with alcohols to produce 4-alkoxy-3-hydroxyesters and their isomerization into 4-ketoesters using boron trifluoride as the catalyst are presented. Both transformations are simple and efficient methods for the synthesis of the above named synthetically useful compounds., (© 2011 American Chemical Society)

We have synthesized nine beta-hydroxy-alpha-sulfenyl-gamma-butyrolactones having different substituents. The syn-anti or syn-syn lactones (or any mixture of both) invariably isomerized into syn-anti/syn-syn lactones in a ratio of approximately 6/4. The other two possible isomeric lactones (anti-syn or anti-anti) were never observed. The crystal structures of syn-syn lactones have been determined. We found sulfur-oxygen distances to be less than the sum of the van der Waals radii (3.3 A), with the angle formed among the hydroxylic oxygen, sulfur, and quaternary aromatic carbon being close to 180 degrees. In addition, carbonylic oxygen-sulfur is directed <40 degrees from the perpendicular to the C-S-C. Theoretical calculations were performed which emphasize the directionality of the sulfur-oxygen interaction. The X-ray and theoretical studies demonstrate that two concomitant, attractive 1,4 intramolecular interactions of divalent sulfur with both carbonyl and hydroxyl oxygens are the driving force for the aforementioned stereochemical preference. Then nonbonded sulfur-oxygen interactions would control the stereoselectivity of the reaction. The same features are observed in the X-ray structure of a beta-hydroxy-alpha-sulfinyl-gamma-butyrolactone.

The dipeptidyl epoxyesters 3 and 4 are potent, irreversible inhibitors of cruzain and rhodesain.

The diastereoselectivity of the nucleophilic epoxidation of gamma-hydroxy-alpha,beta-unsaturated esters having a methyl substituent at the alpha- or beta-position was investigated. Epoxidation of the alpha-methyl-substituted enoate was highly stereoselective, giving rise to the syn isomer. This finding was used to perform an enantioselective synthesis of a natural product having a beta-hydroxy-alpha-methylene-gamma-butyrolactone motif. The nucleophilic epoxidation of enoates was found to be irreversible. Models to explain the observed stereoselectivities are proposed.

This article presents climate change as the major environmental problem of our time. A result of the so-called "greenhouse effect", climate change is caused by certain gases, the concentrations in the atmosphere of which are growing exponentially. The consequences of these gases are going to be felt throughout the entire biosphere, from weather phenomenon to humans, creating a uncertain panorama which is going to be requiring some fast-paced adaptation on the part of all species. This is not, however, an irreversible process, taking action thus being possible and necessary, by combining education and lawmaking measures brought into being within the timeframes and to the extents set forth under the 1997 Kyoto Protocol. Spain will be one of the most highly-affected countries, and its strategy may therefore mean a highly-valuable tool for correcting the deviations caused and contributing to the urgent control of global emissions.

A novel peroxidase that catalyses the transformation of caffeic acid and ferulic acid via oxidative coupling was purified from callus cultures of Bupleurum salicifolium petioles. The enzyme, which was purified over 2,900-fold, is a glycoprotein with a molecular weight of 38,000, determined by SDS/PAGE and gel filtration. The K(m) values obtained were 2.4x10(-4) M for caffeic and 2.6x10(-4) M for ferulic acid, while the K(m) values for H2O2 with caffeic acid was 4x10(-5) M and for H2O2 with ferulic acid was 4.8x10(-4) M. The purified peroxidase exhibits lower activity with typical peroxidase substrates (guaiacol and pyrogallol) than it does with caffeic and ferulic acids, but does not exhibit any activity with other phenylpropanoids tested (cinnamic acid, coumaric acid, and 3,4-dimethoxycinnamic acid).

The dipeptidyl epoxy ketone 4 is a potent, irreversible inhibitor of cruzain, a cysteine protease isolated from Trypanosoma cruzi, with an apparent second order inhibition rate constant of 330,000 sec-1M-1.