Iron(III) complexation by Vanchrobactin, a siderophore of the bacterial fish pathogen Vibrio anguillarum

The bacterial fish pathogen Vibrio anguillarum serotype O2 strain RV22 produces the mono catecholate siderophore Vanchrobactin (Vb) under conditions of iron deficiency. Vb contains two potential bidentate coordination sites: catecholate and salicylate groups. The iron(iii) coordination properties of Vb is investigated in aqueous solutions using spectrophotometric and potentiometric methods. The stepwise equilibrium constants (logK) for successive addition of Vb dianion to a ferric ion are 19.9; 13.3, and 9.5, respectively, for an overall association constant of 42.7. Based on the previous results, we estimated the equilibrium concentration of free iron(iii) under physiological conditions for pH 7.4 solution containing 10-6 M total iron and 10-5 M total Vb as pFe = 20 (=-log[Fe3+]). The Vb model compounds catechol (Cat) and 2,4-dihydroxy-N-(2-hydroxyethyl)benzamide (Dhb) have also been examined, and the obtained results show that the interaction of the whole system of Vb that contains the ferric-chelating groups of both Dhb and Cat, is synergically greater than the separate parts; i.e. Vb is the best chelating agent either in acid or basic media. In summary, bacteria employing Vb-mediated iron transport thus are able to compete effectively for iron with other microorganisms within which they live.Ministerio de Educación y Ciencia; CTQ2008-04429Ministerio de Educación y Ciencia; CTQ2005-00793Galicia. Consellería de Economía e Industria; 10PXIB103157P

Ethyl 1-O-tert-butyl­dimethyl­silyl-2,3-O-isopropyl­idene-5-[(2′S)-tetra­hydro­pyran-2-yl­oxy]-d-glycero-α-d-manno-hepto­furonate

The title compound {systematic name: (2S,3R)-ethyl 3-[(3aS,4R,6S,6aS)-6-tert-butyl­dimethyl­silyl­oxy-2,2-dimethyl­per­hydro­furo[3,4-d][1,3]dioxol-4-yl]-2-nitro-3-[(S)-tetra­hydro-2H-pyran-2-yl­oxy]propanoate}, C23H41NO10Si, is the product of the Henry reaction of 1-O-tert-butyl­dimethyl­silyl-2,3-O-isopropyl­idene-α-d-lyxo-penta­dialdo-1,4-furan­ose with ethyl nitro­acetate and the subsequent protection of its C-5 hydr­oxy group as tetra­hydro­pyranyl, in order to avoid the retro-Henry reaction. The tetra­hydro­pyranyl group adopts a chair conformation. The absolute configuration, assumed from the synthesis, was confirmed from the diffraction data

Stereoselective Synthesis of Orthogonally Protected 1,2-Diaminoinositols from D-Mannose

We present herein a promising novel strategy for the transformation of sugar aldehydes into 1,2-diaminoinositols. This process, based on the sequential intermolecular aza-Henry reaction and intermolecular Henry reaction allowed the total synthesis of a 1,2-diaminoinositols with total stereochemical control. The new route constitutes a simpler and more efficient approach than those previously described routes to 1,2-diaminoinositols and it has the additional advantage of offering the possibility of orthogonal protection of the amino groups

Gold(III) Complexes Activity Against Multidrug-Resistant Bacteria Of Veterinary Significance

The emergence and spread of multidrug-resistant bacteria are a global concern. The lack of new antibiotics in the pipeline points to the need for developing new strategies. In this sense, gold(III) complexes (G3Cs) could be a promising alternative due to their recently described antibacterial activity. The aim of this study was to evaluate the antimicrobial activity of G3Cs alone and in combination with colistin against pathogenic bacteria from veterinary sources. Minimal inhibitory concentration (MIC) values were determined by broth microdilution and compared with clinically relevant antibiotics. Antibiofilm activity was determined by crystal violet staining. Combinations of selected G3Cs with colistin and cytotoxicity in commercial human cell lines were evaluated. Four and seven G3Cs showed antibacterial effect against Gram-negative and Gram-positive strains, respectively, with this activity being higher among Gram-positive strains. The G3Cs showed antibiofilm activity against Gram-negative species at concentrations similar or one to four folds higher than the corresponding MICs. Combination of G3Cs with colistin showed a potential synergistic antibacterial effect reducing concentrations and toxicity of both agents. The antimicrobial and antibiofilm activity, the synergistic effect when combined with colistin and the in vitro toxicity suggest that G3Cs would provide a new therapeutic alternative against multidrug-resistant bacteria from veterinary origin

Novel gold(III)-dithiocarbamate complex targeting bacterial thioredoxin reductase: antimicrobial activity, synergy, toxicity, and mechanistic insights

IntroductionAntimicrobial resistance is a pressing global concern that has led to the search for new antibacterial agents with novel targets or non-traditional approaches. Recently, organogold compounds have emerged as a promising class of antibacterial agents. In this study, we present and characterize a (C^S)-cyclometallated Au(III) dithiocarbamate complex as a potential drug candidate.Methods and resultsThe Au(III) complex was found to be stable in the presence of effective biological reductants, and showed potent antibacterial and antibiofilm activity against a wide range of multidrug-resistant strains, particularly gram-positive strains, and gram-negative strains when used in combination with a permeabilizing antibiotic. No resistant mutants were detected after exposing bacterial cultures to strong selective pressure, indicating that the complex may have a low propensity for resistance development. Mechanistic studies indicate that the Au(III) complex exerts its antibacterial activity through a multimodal mechanism of action. Ultrastructural membrane damage and rapid bacterial uptake suggest direct interactions with the bacterial membrane, while transcriptomic analysis identified altered pathways related to energy metabolism and membrane stability including enzymes of the TCA cycle and fatty acid biosynthesis. Enzymatic studies further revealed a strong reversible inhibition of the bacterial thioredoxin reductase. Importantly, the Au(III) complex demonstrated low cytotoxicity at therapeutic concentrations in mammalian cell lines, and showed no acute in vivo toxicity in mice at the doses tested, with no signs of organ toxicity.DiscussionOverall, these findings highlight the potential of the Au(III)-dithiocarbamate scaffold as a basis for developing novel antimicrobial agents, given its potent antibacterial activity, synergy, redox stability, inability to produce resistant mutants, low toxicity to mammalian cells both in vitro and in vivo, and non-conventional mechanism of action

Modern Synthetic Methods for the Stereoselective Construction of 1,3-Dienes

The 1,3-butadiene motif is widely found in many natural products and drug candidates with relevant biological activities. Moreover, dienes are important targets for synthetic chemists, due to their ability to give access to a wide range of functional group transformations, including a broad range of C-C bond-forming processes. Therefore, the stereoselective preparation of dienes have attracted much attention over the past decades, and the search for new synthetic protocols continues unabated. The aim of this review is to give an overview of the diverse methodologies that have emerged in the last decade, with a focus on the synthetic processes that meet the requirements of efficiency and sustainability of modern organic chemistry

Synthesis of Spironucleosides: Past and Future Perspectives

Spironucleosides are a type of conformationally restricted nucleoside analogs in which the anomeric carbon belongs simultaneously to the sugar moiety and to the base unit. This locks the nucleic base in a specific orientation around the N-glycosidic bond, imposing restrictions on the flexibility of the sugar moiety. Anomeric spiro-functionalized nucleosides have gained considerable importance with the discovery of hydantocidin, a natural spironucleoside isolated from fermentation broths of Streptomyces hygroscopicus which exhibits potent herbicidal activity. The biological activity of hydantocidin has prompted considerable synthetic interest in this nucleoside and also in a variety of analogues, since important pharmaceutical leads can be found among modified nucleoside analogues. We present here an overview of the most important advances in the synthesis of spironucleosides

Imidazol(in)ium-2-Thiocarboxylate Zwitterion Ligands: Structural Aspects in Coordination Complexes

Azolium-2-thiocarboxylate zwitterion ligands have emerged as a promising class of compounds in the field of coordination chemistry due to their unique structural features and versatile applications. These ligands are characterized by a positively charged azolium ring and a negatively charged thiocarboxylate moiety, making them capable of forming stable coordination complexes with various metal ions. One of the key structural aspects that make these ligands attractive for coordination chemistry is their ability to adopt diverse coordination modes with metal centers. The nature of these ligands enables them to engage in both monodentate and bidentate coordination, resulting in the formation of chelated complexes with enhanced stability and controlled geometry or the formation of polynuclear structures. This versatility in coordination behavior allows for the design of tailored ligands with specific metal-binding preferences, enabling the creation of unique and finely tuned coordination architectures. The azolium-2-thiocarboxylate zwitterionic ligands offer a promising platform for the design of coordination complexes with diverse structural architectures