Artículos (Química Orgánica)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10924

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1,4-Dideoxy-1,4-imino-d-arabinitol (DAB) Analogues Possessing a Hydrazide Imide Moiety as Potent and Selective α-Mannosidase Inhibitors
(American Chemical Society, 2020) Haarr, Marianne B.; López López, Óscar; Pejov, Ljupcho; Fernández-Bolaños Guzmán, José María; Lindbäck, Emil; Sydnes, Magne O.; Universidad de Sevilla. Departamento de Química orgánica
The synthesis of two polyhydroxylated pyrrolidines as 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) analogues bearing a hydrazide moiety is described. The DAB analogues act as selective and potent inhibitors of α-mannosidase in the submicromolar concentration ranges (Ki values ranging from 0.23 to 1.4 μM).
2-Aminobenzoxazole-appended coumarins as potent and selective inhibitors of tumour-associated carbonic anhydrases
(Taylor & Francis, 2022) Fuentes Aguilar, Alma; Merino Montiel, Penélope; Montiel Smith, Sara; Meza Reyes, Socorro; Vega Báez, José Luis; Fernández-Bolaños Guzmán, José María; López López, Óscar; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Junta de Andalucía; Gobierno de Canarias
We have carried out the design, synthesis, and evaluation of a small library of 2-aminobenzoxazole-appended coumarins as novel inhibitors of tumour-related CAs IX and XII. Substituents on C-3 and/or C-4 positions of the coumarin scaffold, and on the benzoxazole moiety, together with the length of the linker connecting both units were modified to obtain useful structure-activity relationships. CA inhibition studies revealed a good selectivity towards tumour-associated CAs IX and XII (Ki within the mid-nanomolar range in most of the cases) in comparison with CAs I, II, IV, and VII (Ki > 10 µM); CA IX was found to be slightly more sensitive towards structural changes. Docking calculations suggested that the coumarin scaffold might act as a prodrug, binding to the CAs in its hydrolysed form, which is in turn obtained due to the esterase activity of CAs. An increase of the tether length and of the substituents steric hindrance was found to be detrimental to in vitro antiproliferative activities. Incorporation of a chlorine atom on C-3 of the coumarin moiety achieved the strongest antiproliferative agent, with activities within the low micromolar range for the panel of tumour cell lines tested.
25th Anniversary of Molecules—Recent Advances in Green Chemistry
(Multidisciplinary Digital Publishing Institute (MDPI), 2021) Gonzalo Calvo, Gonzalo de; Freire, Mara G.; Universidad de Sevilla. Departamento de Química orgánica
A 3D Peptide/[60]Fullerene Hybrid for Multivalent Recognition
(Wiley-Blackwell, 2022-10-10) Gallego, Iván; Ramos-Soriano, Javier; Méndez Ardoy, Alejandro; Cabrera González, Justo; Lostalé Seijo, Irene; Illescas, Beatriz M.; Reina, José J.; Martín, Nazario; Montenegro, Javier; Universidad de Sevilla. Departamento de Química orgánica; Agencia Estatal de Investigación. España; Xunta de Galicia; European Union (UE); Human Frontier Science Program (HFSP); Ministerio de Universidades. España; Comunidad Autónoma de Madrid
Fully substituted peptide/[60]fullerene hexakis-adducts offer an excellent opportunity for multivalent protein recognition. In contrast to monofunctionalized fullerene hybrids, peptide/[60]fullerene hexakis-adducts display multiple copies of a peptide in close spatial proximity and in the three dimensions of space. High affinity peptide binders for almost any target can be currently identified by in vitro evolution techniques, often providing synthetically simpler alternatives to natural ligands. However, despite the potential of peptide/[60]fullerene hexakis-adducts, these promising conjugates have not been reported to date. Here we present a synthetic strategy for the construction of 3D multivalent hybrids that are able to bind with high affinity the E-selectin. The here synthesized fully substituted peptide/[60]fullerene hybrids and their multivalent recognition of natural receptors constitute a proof of principle for their future application as functional biocompatible materials.
A Bicyclic 1-Deoxygalactonojirimycin Derivative as a Novel Pharmacological Chaperone for GM1 Gangliosidosis
(Cell Press, 2013) Takai, Tomoko; Higaki, Katsumi; Aguilar Moncayo, Matilde; Mena Barragán, Teresa; Hirano, Yuki; Yura, Kei; García Moreno, M. Isabel; Ortiz Mellet, Carmen; García Fernández, José Manuel; Suzuki, Yoshiyuki; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia e Innovación (MICIN). España; Fundación Ramón Areces; Junta de Andalucía; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); European Commission. Fondo Social Europeo (FSO)
Lysosomal β-galactosidase (β-Gal) deficiency causes a group of disorders that include neuronopathic GM1 gangliosidosis and non-neuronopathic Morquio B disease. We have previously proposed the use of small molecule ligands of β-Gal as pharmacological chaperones (PCs) for the treatment of GM1 gangliosidosis brain pathology. Although it is still under development, PC therapy has yielded promising preclinical results in several lysosomal diseases. In this study, we evaluated the effect of bicyclic 1-deoxygalactonojirimycin (DGJ) derivative of the sp2-iminosugar type, namely 5N,6S-(N′-butyliminomethylidene)-6-thio-1- deoxygalactonojirimycin (6S-NBI-DGJ), as a novel PC for human mutant β-Gal. In vitro, 6S-NBI-DGJ had the ability to inhibit the activity of human β-Gal in a competitive manner and was able to protect this enzyme from heat-induced degradation. Computational analysis supported that the rigid glycone bicyclic core of 6S-NBI-DGJ binds to the active site of the enzyme, with the aglycone N′-butyl substituent, in a precise E-orientation, located at a hydrophobic region nearby. Chaperone potential profiling indicated significant increases of enzyme activity in 24 of 88 β-Gal mutants, including four common mutations. Finally, oral administration of 6S-NBI-DGJ ameliorated the brain pathology of GM1 gangliosidosis model mice. These results suggest that 6S-NBI-DGJ is a novel PC that may be effective on a broad range of β-Gal mutants.
A broadened scope for the use of hydrazones as neutral nucleophiles in the presence of H-bonding organocatalysts
(2006) Pettersen, Daniel; Perez Herrera, Raquel; Bernardi, Luca; Fini, Franscesco; Sgarzani, Valentina; Fernández Fernández, Rosario Fátima; Lassaletta Simón, José María; Ricci, Alfredo; Universidad de Sevilla. Departamento de Química orgánica
Using thioureas as H-bonding organocatalysts, nitroalkenes can be activated for the conjugate addition of hydrazones as neutral nucleophiles. Formaldehyde derivatives react at the azomethine carbon as expected, whereas hydrazones from enolizable aldehydes behave as ene-hydrazines and react at the α-carbon instead. Ionic liquids were found to decrease the reaction times considerably compared to commonly used solvents, whereas alternative activation by Lewis acids resulted in decomposition of reactants.
A Complex Regulatory Network Governs the Expression of Symbiotic Genes in Sinorhizobium Fredii HH103
(Frontiers Media, 2023) Navarro Gómez, Pilar; Fuentes Romero, Francisco; Pérez Montaño, Francisco de Asís; Jiménez Guerrero, Irene; Alías Villegas, Cynthia; Ayala García, Paula; Almozara, Andrés; Medina Morillas, Carlos; Ollero Márquez, Francisco Javier; Rodríguez Carvajal, Miguel Ángel; Ruiz Sainz, José Enrique; López Baena, Francisco Javier; Vinardell González, José María; Acosta Jurado, Sebastián; Universidad de Sevilla. Departamento de Microbiología; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia e Innovación (MICIN). España
Introduction: The establishment of the rhizobium-legume nitrogen-fixing symbiosis relies on the interchange of molecular signals between the two symbionts. We have previously studied by RNA-seq the effect of the symbiotic regulators NodD1, SyrM, and TtsI on the expression of the symbiotic genes (the nod regulon) of Sinorhizobium fredii HH103 upon treatment with the isoflavone genistein. In this work we have further investigated this regulatory network by incorporating new RNA-seq data of HH103 mutants in two other regulatory genes, nodD2 and nolR. Both genes code for global regulators with a predominant repressor effect on the nod regulon, although NodD2 acts as an activator of a small number of HH103 symbiotic genes. Methods: By combining RNA-seq data, qPCR experiments, and b-galactosidase assays of HH103 mutants harbouring a lacZ gene inserted into a regulatory gene, we have analysed the regulatory relations between the nodD1, nodD2, nolR, syrM, and ttsI genes, confirming previous data and discovering previously unknown relations. Results and discussion: Previously we showed that HH103 mutants in the nodD2, nolR, syrM, or ttsI genes gain effective nodulation with Lotus japonicus, a model legume, although with different symbiotic performances. Here we show that the combinations of mutations in these genes led, in most cases, to a decrease in symbiotic effectiveness, although all of them retained the ability to induce the formation of nitrogen-fixing nodules. In fact, the nodD2, nolR, and syrM single and double mutants share a set of Nod factors, either overproduced by them or not generated by the wild-type strain, that might be responsible for gaining effective nodulation with L. japonicus.
A Dynamic Kinetic Asymmetric Heck Reaction for the Simultaneous Generation of Central and Axial Chirality
(American Chemical Society, 2018) Carmona, José A.; Hornillos, Valentín; Ramírez López, Pedro; Ros Lao, Abel; Iglesias Sigüenza, Francisco Javier; Gómez-Bengoa, Enrique; Fernández Fernández, Rosario Fátima; Lassaletta Simón, José María; Universidad de Sevilla. Departamento de Química orgánica
A highly diastereo- and enantioselective, scalable Pd-catalyzed dynamic kinetic asymmetric Heck reaction of heterobiaryl sulfonates with electron-rich olefins is described. The coupling of 2,3-dihydrofuran or N-boc protected 2,3-dihydropyrrole with a variety of quinoline, quinazoline, phthalazine, and picoline derivatives takes place with simultaneous installation of central and axial chirality, reaching excellent diastereo- and enantiomeric excesses when in situ formed [Pd0/DM-BINAP] was used as the catalyst, with loadings reduced down to 2 mol % in large scale reactions. The coupling of acyclic, electron-rich alkenes can also be performed using a [Pd0/Josiphos ligand] to obtain axially chiral heterobiaryl α-substituted alkenes in high yields and enantioselectivities. Products from Boc-protected 2,3-dihydropyrrole can be easily transformed into N,N ligands or appealing axially chiral, bifunctional proline-type organocatalysts. Computational studies suggest that a β-hydride elimination is the stereocontrolling step, in agreement with the observed stereochemical outcome of the reaction.
A Dynamic Kinetic C-P Cross-Coupling for the Asymmetric Synthesis of Axially Chiral P,N Ligands
(American Chemical Society, 2016) Ramírez López, Pedro; Ros, Abel; Estepa, Beatriz; Fernández Fernández, Rosario Fátima; Fiser, Béla; Gómez-Bengoa, Enrique; Lassaletta, José M.; Universidad de Sevilla. Departamento de Química Orgánica; Ministerio de Economía y Competitividad (MINECO). España; Junta de Andalucía
The Pd-catalyzed enantioselective C-P cross-coupling between racemic, configurationally stable heterobiaryl triflates and trialkylsilyldiaryl(dialkyl)phosphines has been used for the synthesis of several families of enantiomerically enriched heterobiaryl phosphines including QUINAP, PINAP, and QUINAZOLINAP analogues, which can be performed with good yields and enantioselectivities using JOSIPHOS-type bidentate phosphines. The strategy relies on two key assumptions: (I) The N atom of the heterocycle is a better ligand than triflate, and upon oxidative addition, it incorporates into the coordination sphere of the Pd center to form cationic cyclic intermediates. (II) The geometry of the palladacycle results in a widening of the angles involved in the stabilization of the stereogenic axis, facilitating a fast interconversion of diastereomeric structures and, hence, a dynamic kinetic C-P cross-coupling reaction. These starting hypotheses are supported by experimental and computational studies.
A gliclazide complex based on palladium towards Alzheimer's disease: promising protective activity against Aβ-induced toxicity in C. elegans
(Royal Society of Chemistry, 2022) García García, Amalia; Rojas, Sara; Rivas García, Lorenzo; Navarro Hortal, María D.; Romero Márquez, José M.; Fernández-Bolaños Guzmán, José María; López López, Óscar; Rodríguez-Diéguez, Antonio; Universidad de Sevilla. Departamento de Química orgánica
A new palladium coordination compound based on gliclazide with the chemical formula [Pd(glz)2] (where glz = gliclazide) has been synthesized and characterised. The structural characterization reveals that this material consists of mononuclear units formed by a Pd2+ ion coordinated to two molecules of the glz ligand, in which palladium ions exhibit a distorted plane-square coordination sphere. This novel material behaves like a good and selective inhibitor of butyrylcholinesterase, one of the most relevant therapeutic targets against Alzheimer’s disease. Analysis of the enzyme kinetics showed a mixed mode of inhibition, the title compound being capable of interacting with both the free enzyme and the enzyme–substrate complex. Finally, the palladium compound shows promising protective activity against Ab-induced toxicity in the Caenorhabditis elegans model, which has never been reported.
A hybrid of 1-deoxynojirimycin and benzotriazole induces preferential inhibition of butyrylcholinesterase (BuChE) over acetylcholinesterase (AChE).
(Taylor and Francis Group, 2022) Evangelista, Tereza Cristina Santos; López López, Óscar; Puerta, Adrián; Fernandes, Miguel X.; Ferreira, Sabrina Baptista; Fernández-Bolaños Guzmán, José María; Lindback, Emil; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Junta de Andalucía; Universidad de Sevilla. FQM134: Química Fina de Carbohidratos
The synthesis of four heterodimers in which the copper(I)-catalysed azide-alkyne cycloaddition wasemployed to connect a 1-deoxynojirimycin moiety with a benzotriazole scaffold is reported. The hetero-dimers were investigated as inhibitors against acetylcholinesterase (AChE) and butyrylcholinesterase(BuChE). The heterodimers displayed preferential inhibition (>9) of BuChE over AChE in the micromolarconcentration range (IC50¼7–50mM). For the most potent inhibitor of BuChE, Cornish-Bowden plots wereused, which demonstrated that it behaves as a mixed inhibitor. Modelling studies of the same inhibitordemonstrated that the benzotriazole and 1-deoxynojirimycin moiety is accommodated in the peripheralanionic site and catalytic anionic site, respectively, of AChE. The binding mode to BuChE was different asthe benzotriazole moiety is accommodated in the catalytic anionic site.
A Multitarget Approach against Neuroinflammation: Alkyl Substituted Coumarins as Inhibitors of Enzymes Involved in Neurodegeneration
(MDPI, 2023-11-25) Berrino, Emanuela; Carradori, Simone; Carta, Fabrizio; Melfi, Francesco; Gallorini, Marialucia; Poli, Giulio; Fernández-Bolaños Guzmán, José María; López López, Óscar; Supuran, Claudiu T.; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Junta de Andalucía; Universidad de Sevilla. FQM134: Química Fina de Carbohidratos
Neurodegenerative disorders (NDs) include a large range of diseases characterized by neural dysfunction with a multifactorial etiology. The most common NDs are Alzheimer’s disease and Parkinson’s disease, in which cholinergic and dopaminergic systems are impaired, respectively. Despite different brain regions being affected, oxidative stress and inflammation were found to be common triggers in the pathogenesis and progression of both diseases. By taking advantage of a multi-target approach, in this work we explored alkyl substituted coumarins as neuroprotective agents, capable to reduce oxidative stress and inflammation by inhibiting enzymes involved in neurodegeneration, among which are Carbonic Anhydrases (CAs), Monoamine Oxidases (MAOs), and Cholinesterases (ChEs). The compounds were synthesized and profiled against the three targeted enzymes. The binding mode of the most promising compounds (7 and 9) within MAO-A and -B was analyzed through molecular modeling studies, providing and explanation for the different selectivities observed for the MAO isoforms. In vitro biological studies using LPS-stimulated rat astrocytes showed that some compounds were able to counteract the oxidative stress-induced neuroinflammation and hamper interleukin-6 secretion, confirming the success of this multitarget approach.
A novel approach to the synthesis of N-substituted 1-C-aminomethyl glycofuranosides
(2006) Vera-Ayoso, Yolanda; Borrachero Moya, Pastora; Cabrera Escribano, Francisca; Gómez Guillén, Manuel; Vogel, Pierre; Universidad de Sevilla. Departamento de Química Orgánica; European Union (UE). FP6; Junta de Andalucía
Reductive amination of formyl C-glycofuranosides, easily available from hexose-derived equatorial-2-OH-glycopyranosides by DAST-promoted ring contraction, afforded N-substituted 1-C-aminomethyl glycofuranosides in most cases in high yield.
A Practical Synthesis of Enantiopure 4,5-Dihydroisoxazole-5-carboxylic Acids
(2005) Ros Lao, Abel; Álvarez González, Eleuterio; Dietrich, Hansjörg; Batarda Fernandes, Rosario; Lassaletta Simón, José María; Universidad de Sevilla. Departamento de Química Orgánica; Ministerio de Ciencia y Tecnología (MCYT). España
The 1,3-dipolar cycloaddition of a variety of aromatic and aliphatic nitrile oxides to 2,5-trans-2,5-diphenylpyrrolidine derived acrylamide and cinnamamide efficiently affords the corresponding 4,5-dihydroisoxazole-5- carboxamides in a highly regio- and stereoselective manner. The cycloaddition of aliphatic nitrile oxides to the analogue methacrylamide proceeds also smoothly to afford the expected cycloadducts in moderate yields and very high regio- and stereoselectivity. In sharp contrast, aromatic nitrile oxides react with the same amide to afford 5-methyl-4,5-dihydroisoxazole-5-carboxamides in higher yields but as near 1:1 mixtures of diastereoisomers. Acid hydrolysis of these products afforded enantiopure 4,5-dihydroisoxazole-5-carboxylic acids. © Georg Thieme Verlag Stuttgart.
A selenoureido-iminoglycolipid transported by zeolitic-imidazolate framework nanoparticles: a novel antioxidant therapeutic approach
(Royal Society of Chemistry, 2023-10-05) Guerrero, Fátima; Carmona, Andrés; Vidal, Victoria; Franco, Ana; Martín-Malo, Alejandro; Carrillo-Carrión, Carolina; Sánchez Fernández, Elena Matilde; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia, Innovación y Universidades de España y Agencia Española de Investigación; Junta de Andalucía
A selenium-containing metal–organic framework with remarkable antioxidant capacity and ROS-scavenging activity was constructed by a controlled de novo encapsulation approach of a glycoconjugate mimetic, specifically a sp2 -iminoglycolipid bearing a selenoureido fragment (DSeU), within a zeolitic-imidazolate framework exoskeleton. Biocompatible and homogeneous nanosized particles of B70 nm (DSeU@ZIF8) were obtained, which could be efficiently internalized in cells, overcoming the poor solubility in biological media and limited bioavailability of glycolipids. The ZIF-particle served as nanocarrier for the intracellular delivery of the selenocompound to cells, promoted by the acidic pH inside endosomes/lysosomes. As demonstrated by in vitro studies, the designed DSeU@ZIF8 nanoparticles displayed a high antioxidant activity at low doses; lower intracellular ROS levels were observed upon the uptake of DSeU@ZIF8 by human endothelial cells. Even more interesting was the finding that these DSeU@ZIF8 particles were able to reverse to a certain level the oxidative stress induced in cells by pre-treatment with an oxidizing agent. This possibility of modulating the oxidative stress in living cells may have important implications in the treatment of diverse pathological complications that are generally accompanied with elevated ROS levels.
A versatile stereocontrolled synthesis of 2-deoxyiminosugarC-glycosides and their evaluation as glycosidase inhibitors
(Royal Society of Chemistry, 2021) Lumbroso, Alexandre; Berthonneau, Clément; Beaudet, Isabelle; Quintard, Jean Paul; Planchat, Aurélien; García Moreno, M. Isabel; Ortiz Mellet, Carmen; Le Grognec, Erwan; Universidad de Sevilla. Departamento de Química orgánica; Institut de Chimie des Substances Naturelles (ICSN). France; Ministère de l'Enseignement Supérieur, de la Recherche et de l’Innovation (MESRI). France; Université de Rennes. France; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
A highly enantioselective synthesis of (R,S) or (S,S)-2,6-disubstituted dehydropiperidines has been previously achieved through Sn/Li transmetalation of the corresponding stannylated dehydropiperidines or of their precursors. Herein, we successively consider their Upjohn’s syn dihydroxylation and their anti-dihydroxylation via an epoxidation reaction followed by epoxide opening reaction. The stereochemical course of these reactions was first reported including the use of appropriate protecting groups before considering the conversion of the obtained compounds into NH or NMe iminosugar hydrochlorides. A primary evaluation of the designed iminosugar C-glycosides as glycosidase inhibitors suggests candidates for the selective inhibition of α-galactosidase, amyloglycosidase and naringinase. Beyond the reported results, the method constitutes a highly modulable route for the synthesis of well stereodefined iminosugar C-glycosides, an advantage which might be used for the design of iminosugars to enhance their biological properties.
A β-Cyclodextrin-Based Nanoparticle with Very High Transfection Efficiency Unveils siRNA-Activated TLR3 Responses in Human Prostate Cancer Cells
(Multidisciplinary Digital Publishing Institute (MDPI), 2022) de la Torre, Cristina; Játiva, Pablo; Posadas, Inmaculada; Manzanares, Darío; Jiménez Blanco, José Luis; Ortiz Mellet, Carmen; García Fernández, José Manuel; Ceña, Valentín; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Agencia Estatal de Investigación. España; Instituto de Salud Carlos III; Euronanomed Program; Junta de Castilla-La Mancha; Junta de Andalucía; European Cooperation in Science and Technology (COST); European Regional Development Fund
Synthetic double-stranded small interfering RNAs (siRNAs) mimic interference RNAs (RNAi) and can bind target mRNAs with a high degree of specificity, leading to selective knockdown of the proteins they encode. However, siRNAs are very labile and must be both protected and transported by nanoparticles to be efficiently delivered into cells. In this work, we used a Janus-type polycationic amphiphilic β-cyclodextrin derivative to efficiently transfect siRNAs targeting mRNAs encoding mitogen-activated protein kinase (p42-MAPK) or Ras homolog enriched in brain (Rheb) into different cancer cell lines as well as astrocytes. We took advantage of this high transfection efficiency to simultaneously knock down p42-MAPK and Rheb to boost docetaxel (DTX)-mediated toxicity in two human prostate cancer cell lines (LNCaP and PC3). We found that double knockdown of p42-MAPK and Rheb increased DTX-toxicity in LNCaP but not in PC3 cells. However, we also observed the same effect when scramble siRNA was used, therefore pointing to an off-target effect. Indeed, we found that the siRNA we used in this work induced toll-like receptor 3 activation, leading to β-interferon production and caspase activation. We believe that this mechanism could be very useful as a general strategy to elicit an immune response against prostate cancer cells.
Alkoxyamine-cyanoborane adducts: Efficient cyanoborane transfer agents
(Royal Society of Chemistry, 2011) Márquez, José M.; Martínez Castro, Elisa; Gabrielli, Serena; López López, Óscar; Maya Castilla, Inés; Angulo, Manuel; Álvarez, Eleuterio; Fernández-Bolaños Guzmán, José María; Universidad de Sevilla. Departamento de Química orgánica; Dirección General de Investigación (DGI). España; Junta de Andalucía
We report the synthesis of the hitherto unknown zwitterionic alkoxyamino cyanoboranes by reduction of O-alkyloximes with sodium cyanoborohydride; unprecedented cyanoboronated N-alkoxyformamidines were also isolated as by-products. Boronated alkoxyamines were found to be efficient cyanoborane transfer agents towards more basic amines, including aminosugars; they were also successfully transformed into neoglycoconjugates by the neoglycorandomization reaction with reducing sugars.
Ambiphilic boryl groups in a neutral Ni(ii) complex: a new activation mode of H2
(Royal Society of Chemistry, 2021) Ríos Moreno, Pablo; Borge, Javier; Fernández de Córdova Martín, Francisco José; Sciortino, Giuseppe; Lledós, Agustí; Rodríguez, Amor; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Economia, Industria y Competitividad (MINECO). España
The concept of metal–ligand cooperation opens new avenues for the design of catalytic systems that may offer alternative reactivity patterns to the existing ones. Investigations of this concept with ligands bearing a boron center in their skeleton established mechanistic pathways for the activation of small molecules in which the boron atom usually performs as an electrophile. Here, we show how this electrophilic behavior can be modified by the ligand trans to the boron center, evincing its ambiphilic nature. Treatment of diphosphinoboryl (PBP) nickel–methyl complex 1 with bis(catecholato)diboron (B2Cat2) allows for the synthesis of nickel(II) bis-boryl complex 3 that promotes the clean and reversible heterolytic cleavage of dihydrogen leading to the formation of dihydroborate nickel complex 4. Density functional theory analysis of this reaction revealed that the heterolytic activation of H2 is facilitated by the cooperation of both boryl moieties and the metal atom in a concerted mechanism that involves a Ni(II)/Ni(0)/Ni(II) process. Contrary to 1, the boron atom from the PBP ligand in 3 behaves as a nucleophile, accepting a formally protic hydrogen, whereas the catecholboryl moiety acts as an electrophile, receiving the attack from the hydride-like fragment. This manifests the dramatic change in the electronic properties of a ligand by tuning the substituent trans to it and constitutes an unprecedented cooperative mechanism that involves two boryl ligands in the same molecule operating differently, one as a Lewis acid and the other one as a Lewis base, in cooperation with the metal. In addition, reactivity towards different nucleophiles such as amines or ammonia confirmed the electrophilic nature of the Bcat moiety, allowing the formation of aminoboranes.
Amine-linked diglycosides: synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays
(2011) Moreno Clavijo, Elena; Cumpstey, Ian; Frigell, Jens; Pershagen, Elias; Akhtar, Tashfeen; Alonzi, Dominic S.; Butters, Terry D.; Robina Ramírez, Inmaculada; Universidad de Sevilla. Departamento de Química Orgánica

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