Article

Furanose vs. Acyclic forms of carbohydrate ligands. A multinuclear NMR spectroscopy study of the molybdate and tungstate complexes of D-glycero-L-manno-heptose

Authors:
  • Slovak Academy of Sciences, Institute of Chemistry, Centre for Glycomics
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The formation of dinuclear tungstate and molybdate complexes of d-glycero-l-manno-heptose was studied in aqueous solution by 13C and 183W NMR spectroscopy. The chelating aldose is always tetradentate and occurs exclusively in furanose or acyclic hydrated forms, the proportions of which depend on the pH and nature of the metal ion. In the tungstate species, two types of major complexes, noted M (O-2,3,5,6) and L (O-1,2,3,5) according to the site of chelation, involve the ligand in furanose form. In one of the minor tungstate complexes, chelation occurs at the galacto (O-3,4,5,6) site of the acyclic heptose. In the molybdate species, the complex of type M does not exist, and besides the complex of type L, the major species involve the acyclic ligand with either the galacto (O-3,4,5,6) or arabino (O-1,2,3,4) sites of chelation. Multinuclear NMR data are provided for the identification of the various types of complexes. Marked differences were noticed with respect to the complexes of d-mannose, in which species of type L prevailed with both molybdate and tungstate.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... However, only few works address computationally their complexes with either homogeneous 29 or heterogeneous tungstate species. 31 In the present work, we aim at unraveling the structure of carbohydrate-metal complexes in the prototypical case of tungstate-mannose interaction in aqueous solution, 32 as it is the required step for the understanding of the reactivity of those complexes. Mannose can be efficiently converted into platform molecules either in aqueous or organic medium. ...
... Bilik and coworkers proposed dimolybdate complexes for mannose epimerization comprising the hydrated sugar chelating the metallic ion by its O1,2,3,4 deprotonated hydroxyl groups in a sickle arrangement. 12,32 Such observation reveals the possibility of tungsten to catalyze the epimerization of sugars the same way molybdenum does. ...
Article
The control of metal-sugar complexes speciation in solution is crucial in an energy transition context. Herein, the formation of tungstate-mannose complexes is unraveled in aqueous solution using a multitechnique experimental and theoretical approach. 13C nuclear magnetic resonance (NMR), as well as 13C-1H and 1H-1H correlation spectra, analyzed in the light of coordination-induced shift method and conformation analysis, were employed to characterize the structure of the sugar involved in the complexes. X-ray absorption near edge structure spectroscopy was performed to provide relevant information about the metal electronic and coordination environment. The calculation of 13C NMR chemical shifts for a series of tungstate-mannose complexes using density functional theory (DFT) is a key to identify the appropriate structure among several candidates. Furthermore, a parametric study based on several relevant parameters, namely, pH and tungstate concentration, was carried out to look over the change of the nature and concentrations of the complexes. Two series of complexes were detected, in which the metallic core is either in a ditungstate or a monotungstate form. With respect to previous proposals, we identify two new species. Dinuclear complexes involve both α- and β-furanose forms chelating the metallic center in a tetradentate fashion. A hydrate form chelating a ditungstate core is also revealed. One monotungstate complex appears at high pH, in which a tetrahedral tungstate center is bound to α-mannofuranose through a monodentate site at the second deprotonated hydroxyl group. This unequalled level of knowledge opens the door to structure-reactivity relationships.
... Amino group of chitosan was protonated at working pH (2.7) so, the coordination capability of this group was blocked. Coordination of molybdate anions with hydroxyl groups of sugar residues was previously reported in literature (Matulová, Verchere, & Chapelle, 1996;Sauvage, Verchere, & Chapelle, 1996) Our results support the coordination of molybdate anions to hydroxyl groups of chitosan. The proposed role of protonated amino group was stabilization of negative charged heptamolybdate anions to the surface. ...
Article
Water pollution by heavy metals represents a serious problem around the world. Among various treatment techniques for water remediation, adsorption is an effective and versatile method due to the low cost, effectiveness and simplicity. Chitosan is a cationic polysaccharide with an excellent adsorption capacity of heavy metal ions. Chitosan has a high molybdate adsorption capacity (265 ± 1 mg g⁻¹) at 20 °C and pH 2.7. Participation of hydroxyl groups in the adsorption of molybdate anions was confirmed by FT-IR analysis. SEM images showed that morphological surface changes happen after MoVI adsorption. Continuous adsorption data were best fitted by Modified Dose- Response model. Scale-up of continuous processes was achieved applying bed depth service time (BDST) model. Application of chitosan in molybdate removal from real groundwater samples suggest that this polysaccharide is a good option to be used for household purposes.
... Although the known heptitols are currently without assigned function, characterization of a perseitol-K ? complex from Scurrula fusca leaves Phytochem Rev (2017) 16:137-157 147 123 (Ishizu et al. 2001) coupled with the ability of perseitol, volemitol and other heptitols and heptoses to form complexes with tungstate and molybdate Verchère 1991, 1995;Matulová et al. 1996;Chapelle et al. 1998) suggests a role for 7-C sugars and sugar alcohols in metal ion chelation and translocation. ...
Article
Integrated algal pond systems (IAPSs) combine anaerobic and aerobic bioprocesses to affect sewage treatment. The present work describes the isolation and partial characterisation of soluble extracellular polymeric substances (EPSs) associated with microalgal bacterial flocs (MaB-flocs) generated in high rate algal oxidation ponds (HRAOPs) of an IAPS treating domestic sewage. Productivity and change in MaB-flocs concentration, measured as mixed liquor suspended solids (MLSS) between morning (MLSSAM) and evening (MLSSPM) were monitored and the substructure of the MaB-flocs matrix examined by biochemical analysis and Fourier transform infrared spectroscopy (FT-IR). Results show that MaB-flocs from HRAOPs are assemblages of microorganisms produced as discrete aggregates as a result of microbial EPS production. Formation and accumulation of the EPS was stimulated by light. Analysis by FT-IR revealed characteristic carbohydrate enrichment of these polymeric substances. In contrast, FT-IR spectra of EPSs from dark-incubated MaB-flocs confirmed that these polymers contained increased aliphatic and aromatic functionalities relative to carbohydrates. These differences, it was concluded, were due to dark-induced transition from phototrophic to heterotrophic metabolism. The results negate microalgal cell death as a contributor to elevated chemical oxygen demand of IAPS treated water.
... Although the known heptitols are currently without assigned function, characterization of a perseitol-K ? complex from Scurrula fusca leaves (Ishizu et al. 2001) coupled with the ability of perseitol, volemitol and other heptitols and heptoses to form complexes with tungstate and molybdate Verchère 1991, 1995;Matulová et al. 1996;Chapelle et al. 1998) suggests a role for 7-C sugars and sugar alcohols in metal ion chelation and translocation. ...
Article
Full-text available
Seven-carbon (7-C) sugars and sugar alcohols are common in higher plants, algae, fungi and bacteria. The biochemical origin and physiological function of these monosaccharides in plants and algae however is not well understood and has not been fully investigated. Here the occurrence, metabolism, and transport of heptuloses, heptitols, and heptoses are integrated in accordance with function to emphasise the importance of these apparently neglected sugars. This therefore is the first comprehensive synthesis of knowledge about 7-C sugar biochemistry, a relatively underexplored area of carbohydrate biology that needs to be integrated into mainstream sugar research. Available information on the metabolism of heptuloses, heptitols, and heptoses in Medicago sativa (alfalfa), Persea americana (avocado), Primula sp., Kalanchoë pinnata, and the red alga Porphyridium sp. was thoroughly investigated and evaluated. Results indicate that 7-C sugars share a common precursor and are products of a TKT-dependent heptulose shunt in which Suc-derived Fru 6-P is converted either to Sed 7-P or mannoheptulose 7-P or both in competent tissues and species. In plants, free heptuloses probably arise as a consequence of phosphatase activity, whereas heptoses appear to be formed by isomerisation of the corresponding phloem translocated heptuloses following import into non-photosynthetic tissue. It is proposed that the major physiological function of 7-C sugars and heptitols, in addition to serving as a carbon sink, involves metal ion chelation, translocation and remobilisation to fulfil nutrient requirements essential for growth and development.
Article
Chapter
IntroductionComplexes of Metals Studied as Groups of the Periodic TableOccurrence of Metal Complexes in Synthesis ReactionsConclusion
Article
Molybdate ion uptake both by raw chitosan and by glutaraldehyde cross-linked chitosan beads was investigated. This study focused on the identification of sorption mechanisms by means of several analytical procedures such as infra-red and reflectance spectrophotometries and CP-MAS 13C NMR analyses. Although the amine functions of glucosamine residues remain the major sites of interaction with the metal species, other functional groups can also be involved. It is certainly the case with carbonyl functions provided by the glutaraldehyde structure in cross-linked sorbents. Due to the large size of the polynuclear hydrolysed molybdate species, the sorption may involve several monomer units, resulting in additional linkages between the polymer chains. This behaviour can be confirmed by the chemical shifts of the carbon atoms observed by CP-MAS 13C NMR on raw chitosan beads, showing that the carbon atoms supporting the amino sites are not the only atoms affected by molybdate ion sorption. Moreover, cross-linking promotes a partial reduction of molybdenum species in the presence of some unreacted aldehyde groups.
Article
Analysis of ¹³ C-NMR spectra has shown that ribose, talose and allose behave as trident donors in their molybdate complexes using hydroxyl groups at C (2) , C (3) and C (4) , whereas lyxose and mannose use hydroxyl groups at C (1) , C (2) and C (3) .
Article
This chapter analyzes the composition of reducing sugars in solution. It elaborates the concepts of relative stabilities of various forms of sugars and elaborates the composition of aldoses, ketoses, and substituted and derived sugars in aqueous solution. Neuclear Magnetic Resonance (NMR) spectrometers have considerably improved over the past few years, and important advances now allow the detection and measurement of components that occur in the range of 0.01 -0.1%. Gas-liquid chromatography (GLC) of trimethylsilyl derivatives has been used to determine the composition of some dozen sugars in water and in pyridine. In the latter solvent, the results agree well with previous determinations; in aqueous solution, however, some of the values for furanoses prove to be too high and the values for idose (presumably mutarotating) rapidly differ considerably from those obtained by NMR spectroscopy. GLC of the trimethylsilyl derivatives is also used for studying the mutarotation of D-fructose. The composition data obtained for the major components agree well with those given by NMR spectroscopy.
Article
Dinuclear molybdate complexes of alditols have been studied in aqueous acidic solution by 95Mo and 13C NMR. Their formation constants were determined by potentiometry. In all complexes, the dimolybdate group was chelated by four vicinal hydroxyls. Two types of complexes were characterized by NMR, depending on the erythro or threo configuration of the central diol group. Their structures were precised using literature crystal data. A single asymmetrical complex of the first type was formed by symmetrical erythro ligands (erythritol, galactitol), while the asymmetrical d-arabinitol and D-mannitol formed pairs of isomeric species of this type. Ligands with complexing sites involving a central threo group (DL-threitol, xylitol) were complexed in a symmetrical manner. D-Glucitol formed four complexes as pairs of each type. Rules relating the stabilities of the complexes to the structures of the ligands are presented.
Article
A potentiometric study showed that aldoses of the lyxo-series: d-lyxose, d-mannose and l-rhamnose, form dinuclear anionic complexes with tungstate or molybdate ions in acidic solutions. 95Mo NMR confirmed this result by revealing the presence of two non-equivalent metal atoms in the molybdate complexes. The corresponding formation constants were determined. The d-lyxose complexes had the higher stabilities, and the WVI complexes were more stable than their MoVI homologues. The 13C NMR spectra were reassigned by means of a 2-D experiment and showed that all three carbohydrates were complexed in pyranose form. The chelating hydroxyl groups were strongly deshielded and displayed increased direct coupling constants 1JCH. It can be concluded that the prevailing species in aqueous acidic solution cannot be furanose complexes similar to that characterized in solid state from molybdate—d-lyxose mixtures.
Article
The structure of a molybdenum(VI) complex of the sugar, lyzose, has been established by the X-ray method.
Article
The formation of dimolybdate complexes of ketoses of the ribo and lyxo series and of aldoses of the lyxo series was investigated by 13C and 1H NMR spectroscopy. All these sugars possess two cis hydroxyl groups adjacent to the anomeric centre and form two different series of complexes involving the furanose forms. The tridentate complexes of 2-ketoses involve the ring HO-3,4 and the cis exocyclic HO-1 of the β (ribo series) or of the α (lyxo series) anomer, whereas the trans anomeric HO-2 is not bound to molybdenum. In the lyxo series, the β anomers form tetradentate complexes involving HO-1,2,3,5 (aldoses) or HO-2,3,4,6 (ketoses), that appear similar to a β-d-lyxofuranose complex already characterized in the solid state. A mixture of tridentate and tetradentate species was obtained in the case of d-tagatose. The relative stabilities of the complexes are discussed.
Article
Aldoses of the arabino and xylo series with molybdate ions in aqueous acidic medium, form tetradentate acyclic complexes which are much weaker than those of the related alditols. The formation constants (Kf) of these complexes were obtained by two independent methods, potentiometry and UV spectrophotometry, which gave values in good agreement. The structures of the complexes with aldoses were shown by 13C NMR spectroscopy to involve the ligand in its acyclic form. A study of the complexes of carbohydrate derivatives proved that the magnitude of Kf was mainly dependent on the configuration of the site of chelation. The lower stabilities of the aldose complexes were due to the endergonic opening of the pyranose heterocycle in the first step of the complex formation. An application to the determination of the equilibrium constant for the ring-opening reaction of aldopyranoses is described. It ultimately allowed the calculation of the proportion of acyclic forms (aldehyde and hydrate) in aqueous solutions of the aldoses in the arabino and xylo series.
Article
Aqueous molybdate complexes of d-allose, d-altrose, d-gulose, and d-idose were studied by 1H and 13C NMR spectroscopy. Different amounts of binuclear tetradentate molybdate complexes. involving the hydrated aldehyde group and the three adjacent hydroxyl groups of the hydrate, i.e., HO-2,3,4, were detected for all the aldoses investigated. In addition, d-altrose and d-idose hydrates preferentially adopt another binuclear tetradentate complex with donor hydroxyl groups HO-2,3,4,5. Both types of binuclear tetradentate molybdate complexes are present in two forms due to a different linkage mode of the asymmetric binuclear molybdate core to the aldose hydrate molecule. Cyclic forms of d-allose and d-gulose predominate in their complexes.
Article
A simple excitation sequence allows fast recognition of carbon multiplicity in 13C n.m.r. spectra of large molecules, with high precision and sensitivity.
Article
Dinuclear tungstate complexes of alditols have been studied in aqueous solution by C-13 and W-183 NMR spectroscopies. Ligands possessing hydroxyl groups in erythro configuration (erythritol, galactitol) formed a series of tetradentate complexes homologous to the known corresponding molybdate erythro compounds. In contrast, ligands with threo hydroxyl groups (threitol, xylitol) formed tridentate complexes different from the tetradentate molybdate threo species. For all alditols, the W-183 NMR spectra showed two sharp tungsten signals separated by 3-7 ppm (erthro series) or congruent-to 60 ppm (threo series). In the erythro complexes, large 3J(W,H) coupling constants (8-10 Hz) were measured and allowed the estimation of the corresponding dihedral angles. A structure that accounts for the asymmetry of the chelating site is proposed for the tridentate threo complexes. The structural difference between the molybdate and tungstate complexes of threo-alditols is discussed in connection with their stabilities and reactivities.
Article
The formation of tungstate complexes of aldoses and ketoses with lyxo configuration was studied in aqueous solution by 13C and 183W NMR spectroscopy. Two series of complexes were structurally characterized, in which the sugars adopt the furanose form and chelate a ditungstate group at a tetradentate site. All sugars form a major complex (type L for lyxo) similar to the molybdate species, in which the sites of chelation, O-1,2,3,5 for aldoses or O-2,3,4,6 for ketoses, involve the anomeric oxygen atom and the side chain atom O-5 or O-6. A second type of complex was identified (type M for manno), in which the sites of chelation are O-2,3,5,6 for d-mannose (tungstate species only) and O-3,4,6,7 for d-manno-heptulose (tungstate and molybdate complexes). The overall equilibrium constants for the formation of the complexes are reported and show that ketoses form stronger complexes than aldoses.
Article
The molybdate-catalyzed C-2 epimerization of aldoses has been investigated by using 13C- and 2H-enriched compounds and 75-MHz 13C NMR spectroscopy. The epimerization product of D-[1-13C]mannose was exclusively D-[2-13C]glucose, demonstrating that the reaction involves a 1,2 shift of the carbon skeleton resulting in inversion of configuration at C-2. All of the aldotetroses, aldopentoses, and aldohexoses examined reacted similarly, producing equilibrium mixtures of the starting [1-13C]aldose and the 2-epimeric 2-13C product. Reaction of D-[1-13C,2H]mannose and D-[1,3-13C,3-2H]mannose in H2O and D-mannose in 2H2O demonstrated that the epimerization occurs without C-3 transposition or C-H bond breaking. Studies with aldose analogues including mannitol, 3-deoxy-D-arabino-hexose, 4-deoxy-D-lyxo-hexose, lactose, and 4,6-O-ethylidene-D-glucose suggest that the reactive molybdate complex involves the carbonyl oxygen and three hydroxylic oxygens of the aldehyde form of aldoses. The rates of reaction are influenced by the ability of the ring forms of the starting aldose to form stable unreactive molybdate complexes. Slower secondary reactions involving the simultaneous inversion of configuration of C-2 and C-3 occur without carbon skeletal rearrangement.
Article
Tungstate complexes of all-three alditols HOCH2(CHOH)(n-2)CH2OH (DL-threitol, xylitol, L-iditol, meso-glyceroido-heptitol) have been studied by multinuclear C-13 and W-183 NMR. Contrary to the corresponding molybdate species in which the ligands are always tetradentate, the tungstate species exhibit structural variety, depending on the pH of formation. Only the tungstate complexes (type M) formed at pH 7 are homologous to the molybdate species. At pH 7-9, the ligands are tridentate and chelate a ditungstate group in an asymmetrical way (type T). The corresponding tungstate complex of glycerol is reported for the first time. At pH 9-12, dinuclear species of a previously unknown type P are slowly formed by the pentadentate xylitol and iditol. The heptitol affords two complexes of type P, in which the sites of chelation are HO-2,3,3,5,6 (major complex) and HO-1,2,3,4,5. A possible structure, in agreement with C-13 and W-183 NMR data, is proposed for complexes of type P in which the presence of two WO6 octahedra linked by an edge is reminiscent of structures of ditungstate subunits of polytungstate ions.
Article
Tungstate complexes of alditols have been studied in aqueous solution by W-183 and C-13 NMR spectroscopies. The ligands used in this work may chelate a ditungstate group through several different sites having erythro or threo configurations and therefore yield mixtures of complexes. The structural type of each complex was defined by the characteristic pattern of its W-183 NMR spectrum, and the sites of chelation were identified by C-13 NMR spectroscopy. Alditols which possess an asymmetrical site of erythro configuration (D-arabinitol, D-mannitol, D-glucitol) form two isomeric complexes, as this tetradentate site can be occupied in two reversed orientations. Ribitol forms a single complex of the same type. A single additional complex is formed when another tridentate site of chelation of threo configuration is available (D-arabinitol, D-glucitol). Perseitol (D-glycero-D-galacto-heptitol) affords a pair of erythro complexes involving the tetradentate HO-2,3,4,5 galacto site, together with a third complex of a novel ''mixed'' bis-dinuclear type. For the latter species, four sharp signals in the W-183 NMR spectrum characterized two ditungstate groups bound respectively to an erythro site (delta-74.2 and -81.4) and a threo site (delta-55.4 and -117.6). These sites were assigned from the C-13 NMR spectrum respectively to the HO-4,5,6,7 and the HO-1,2,3 systems, indicating that the ligand was heptadentate.
Article
1H, 13C, and 183W NMR spectroscopic methods were used for the structural characterization of the tungstate and molybdate complexes of volemitol (d-glycero-d-manno-hepitol) in aqueous solution. The major species (type E) are a pair of isomeric complexes formed at the arabino site in reversed orientation, i.e., HO-1,2,3,4 and HO-4,3,2,1. A single, minor complex is formed at the HO-3,4,5,6 altro site and is shown to be isostructural with the known single complexes of ribitol and d-altritol (type E′). The present NMR results support the hypothesis that complexes of type E′ are weaker than those of type E because they are destabilized by a steric strain due to the interaction of the side chain of the ligand with the site of chelation.
Article
Aqueous solutions of molybdate at 90 degrees bring about the inversion of the C-1-C-2 fragment of aldoses having four or more carbon atoms, generating thermodynamically equilibrated mixtures of the starting aldose and its 2-epimer. In some cases, notably with the aldopentoses, substantial proportions of the 3-epimers are produced, as well as 2-epimers that have not undergone inversion of the C-1-C-2 fragment. These side-reactions can be controlled by using the paramolybdate form of an anion-exchange resin (AG MP-1) together with the formate form of the same resin. The latter acts to scavenge unbound molybdate and paramolybdate anions that appear to be responsible for the side reactions.
  • Alföldi