Lasalocid Anion Research Articles

Spectroscopic, crystallographic and theoretical studies of lasalocid complex with ammonia and benzylamine

A natural antibiotic – Lasalocid is able to form stable complexes with ammonia and organic amines. New complexes of lasalocid with benzylamine and ammonia were obtained in the crystal forms and studied using X-ray, FT-IR, 1H NMR, 13C NMR and DFT methods. These studies have shown that in both complexes the proton is transferred from the carboxylic group to the amine group with the formation of a pseudo-cyclic structure of lasalocid anion complexing the protonated amine or NH4+ cation. The spectroscopic and DFT studies demonstrated that the structure of the complex formed between Lasalocid and benzylamine in the solid is also conserved in the solution and gas phase. In contrast, the structure of the complex formed between lasalocid and ammonium cation found in the solid state undergoes dissociation in chloroform solution accompanied with a change in the coordination form of the NH4+ cation.

Bulk liquid membrane transport of ferrioxamine B by neutral and ionizable carriers

Bulk liquid membrane (BLM) transport of ferrioxamine B (FeHDFB+) across an artificial hydrophobic membrane facilitated by neutral and ionizable carriers was studied. Under controlled conditions, ferrioxamine B transport by neutral ionophores follows a simple theoretical model for a diffusion controlled process which predicts a linear dependence of flux upon aqueous-to-chloroform extraction constants. Unsubstituted 18C6 crown ether exhibits the best transport properties among the neutral carriers investigated with a flux of 1.4 × 10–10 mol s–1 cm–2. When transport of FeHDFB+, metal-free desferrioxamine B, H4DFB+, and AlHDFB+ mediated by DC18C6 crown ether was followed, a selectivity was observed with a ratio of measured relative fluxes of 5∶3∶1, respectively. An ionizable carrier lasalocid {6-[7-[5-ethyl-5-(5-ethyltetrahydro-5-hydroxy-6-methyl-2H-pyran-2-yl)tetrahydro-3-methyl-2-furanyl]-4-hydroxy-3,5-dimethyl-6-oxonoyl]-2-hydroxy-3-methylbenzoic acid}, negatively charged at neutral pH, outperformed the crown ethers as a ferrioxamine B transporting agent. However, transport by ionizable carriers follows a different mechanism and occurs only when an electrolyte is present in the receiving phase. This requirement was exploited by designing a BLM experiment in which H4DFB+ acts as a counter cation at the receiving interface, whereby FeHDFB+ and H4DFB+ were transported in opposite directions in a synergistic fashion. When the ionizable salicylic acid moiety of lasalocid is transformed into an ester, lasalocid almost entirely loses its transporting properties. This suggests a co-operative mode of binding in which electrostatic recognition of the FeHDFB+ cation by lasalocid anion is a prerequisite for a subsequent encapsulation of the amine site in a host–guest fashion.

Two Lasalocid Sodium Salts

The structures of two new forms of lasalocid sodium salt, sodium 6-[7R-{5S-ethyl-5-(5R-ethyltetrahydro-5-hydroxy-6S-methyl-2H-pyran-2R-yl)tetrahydro-3S-methyl-2S-furanyl}-4S-hydroxy-3R,5S-dimethyl-6-oxononyl]-2-hydroxy-3-methylbenzoate (A), Na + .C 34 H 53 O 8 − , and sodium 6-[7R-{5S-ethyl-5-(5R-ethyltetrahydro-5-hydroxy-6S-methyl-2H-pyran-2R-yl)tetrahydro-3S-methyl-2S-furanyl}-4S-hydroxy-3R,5S-dimethyl-6-oxononyl]-2-hydroxy-3-methylbenzoate diethyl ether solvate (B), Na + .C 34 H 53 O 8 − .C 4 H 10 O, are reported. Form A exist as a «head-to-head» dimer, while form B is a «head-to-tail» dimer. Sodium is coordinated to six O atoms from the lasalocid anion in both forms, but the coordination spheres differ. Form A contains a bridging carbonyl O atom, but, remarkably, the carboxylate group does not coordinate to the sodium ion. In form B, the carbonyl O atom does not bridge but there is a direct carboxylate-sodium interaction

Interactions between metal cations and the ionophore lasalocid. Part 13. Structure of 1:1 and 2:1 lasalocid anion–divalent cation complexes in methanol

The successive formation of complexes MA+ and MA2 of alkaline-earth cations M2+ with lasalocid HA is observable in methanol. Knowing the corresponding formation constants, it was possible to access NMR parameters specific to these two types of species for the four alkaline-earth cations. 13C and 1H chemical shifts are reported for MA+ and MA2; 1H–1H coupling constants for MA+ only. Experiments at low temperature and experiments using the paramagnetic cation Mn2+ determined the coordination sites. All these data show an appreciable variability of coordination in the series of alkaline-earth cations. Computations using the semi-empirical quantum methods AM1 and PM3 and Monte-Carlo simulations in methanol according to BOSS, mainly on MgA+ and BaA+ fully confirmed these findings.

Evidence for self-aggregation of the ionophore lasalocid free anion in aqueous solution

Surface tension, conductivity and NMR data for tetraaikylammonium salts of lasalocid in water show that they behave as surfactants; their high solubility thus involves lasalocid anion self-aggregation.

Interactions between metal cations and the ionophore lasalocid. Part 8.—Enthalpies and entropies of formation of 1 : 1 and 2 : 1 complexes of lasalocid anion and salicylate with some divalent transition-metal cations in methanol

Complexation in methanol of Mn2+, Fe2+, Co2+, Ni2+ and Zn2+ cations by lasalocid and salicylic acid has been studied using reaction calorimetry. Formation of the two successive complexes AM+ and A2M of the acid ligand, AH, with cations M2+ has previously been shown to occur, and was confirmed here. Enthalpies of formation of the complexes AM+ and A2M were simultaneously determined using a novel calorimetric method. The corresponding entropies could then be obtained from the previously recorded Gibbs functions. Compared with the other cations, Fe2+ shows very specific behaviour corresponding to stronger interactions and more rigid structures. For a given cation there is no large difference between analogous thermodynamic functions obtained for lasalocid and for the model species salicylic acid. It is suggested that in the lasalocid anion the salicylate group is the main coordination site in methanol for the cations studied here.

Interactions between metal cations and the ionophore lasalocid. Part 6.—Potentiometric and electron spin resonance study of the complexation of Gd3+ in methanol by lasalocid and simpler carboxylic acids

Complexes formed in methanol between the ionophore lasalocid and the Gd3+ ion have been studied using pHmetric, e.s.r. and u.v.–visible titration against tetrabutylammonium methoxide solution. The same has been done for salicylic and benzoic acids. In all cases the formation of the successive complexes AGd2+, A2Gd+ and A3Gd between the acid AH and the Gd3+ion has been observed and the corresponding formation constants were determined. More or less strong variation of the height, width and intensity of the e.s.r. line has been observed with the formation of the complexes; individual e.s.r. parameters could be had for most of the complexes. Comparison of data obtained for lasalocid and salicylic or benzoic acid suggests that in lasalocid anion–gadolinium cation complexes in methanol, the carboxylate group is the main and possibly the sole binding site of the gadolinium ion. Other complexes are formed in more basic media in methanol; these may involve the salicylate dianion, as shown for salicylic acid–gadolinium complexes, or, more probably, result from successive substitution of a methoxide ion for a lasalocid anion in A3Gd.

Interactions between metal cations and the ionophore lasalocid. Part 7.—Heat capacities and volumes of complexation of lasalocid with alkali-metal and alkaline-earth-metal cations in methanol

Volume changes and heat-capacity changes for the formation in methanol of the 1–1 complexes of the ionophore lasalocid anion with either the alkali-metal cations or the alkaline-earth-metal cations have been obtained from density and calorimetric measurements. The data obtained are discussed in relation to what is known about the structure of these various complexes in solution. The peculiar behaviour of lithium and magnesium ions with respect to the other cations in each series is stressed, heat capacity–entropy correlations being particularly significant. In agreement with the structural features, this could be due to the fact that in these particular complexes, the ligand has more degrees of freedom and that the cation and possibly the carboxylate group of the ligand remain more solvated. Complexation volumes and heat capacities of the other cations vary more or less regularly depending on the size and charge of the cation.

ChemInform Abstract: Interactions Between Metal Cations and the Ionophore Lasalocid (I). Part 4. δH‐ and δS‐ for Formation of 1:1 and 2:1 Complexes of the Lasalocid Anion and Salicylate with Alkaline‐Earth Metal Cations in Methanol.

ChemInformVolume 19, Issue 36 Article ChemInform Abstract: Interactions Between Metal Cations and the Ionophore Lasalocid (I). Part 4. δH- and δS- for Formation of 1:1 and 2:1 Complexes of the Lasalocid Anion and Salicylate with Alkaline-Earth Metal Cations in Methanol. Y. POINTUD, Y. POINTUD Lab. Etud. Interact. Solutes-Solvants, CNRS, Univ. Blaise Pascal, 63170-Aubiere, Fr.Search for more papers by this authorE. PASSELAIGUE, E. PASSELAIGUE Lab. Etud. Interact. Solutes-Solvants, CNRS, Univ. Blaise Pascal, 63170-Aubiere, Fr.Search for more papers by this authorJ. JUILLARD, J. JUILLARD Lab. Etud. Interact. Solutes-Solvants, CNRS, Univ. Blaise Pascal, 63170-Aubiere, Fr.Search for more papers by this author Y. POINTUD, Y. POINTUD Lab. Etud. Interact. Solutes-Solvants, CNRS, Univ. Blaise Pascal, 63170-Aubiere, Fr.Search for more papers by this authorE. PASSELAIGUE, E. PASSELAIGUE Lab. Etud. Interact. Solutes-Solvants, CNRS, Univ. Blaise Pascal, 63170-Aubiere, Fr.Search for more papers by this authorJ. JUILLARD, J. JUILLARD Lab. Etud. Interact. Solutes-Solvants, CNRS, Univ. Blaise Pascal, 63170-Aubiere, Fr.Search for more papers by this author First published: September 6, 1988 https://doi.org/10.1002/chin.198836075AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue36September 6, 1988 RelatedInformation

Interactions between metal cations and the ionophore lasalocid. Part 4.—ΔH⊖ and ΔS⊖ for formation of 1–1 and 2–1 complexes of the lasalocid anion and salicylate with alkaline-earth metal cations in methanol

Enthalpies of formation of 1–1 and 2–1 complexes of the lasalocid anion and salicylate with alkaline-earth metal cations in methanol have been obtained from calorimetric measurements. The corresponding entropies were obtained from previously determined stability constants. Involvement in the complexation of the salicylate part of the lasalocid anion was thereby assessed. For 1–1 complexes, the results point to a transition from an extended conformation for the lasalocid anion in the magnesium complex to a folded one in the barium complex. For 2–1 complexes bonding of the second lasalocid anion may not be solely due to the salicylate moiety. Finally, the ionophoric power of lasalocid with respect to alkaline-earth metal cations is discussed.

Free acid, anion, alkali, and alkaline earth complexes of lasalocid a (X537A) in methanol: structural and kinetic studies at the monomer level.

We report below on nuclear magnetic resonance investigations of the structure and exchange kinetics for the free acid, anion, sodium complex, and barium complex of the ionophore lasalocid A (X537A) in methanol solution. A comparison between the proton and carbon longitudinal relaxation times of lasalocid in nonpolar and polar solvents demonstrates that the free acid (HX) is a monomer in methanol solution. Parallel proton and carbon relaxation measurements demonstrate that the anion (X-), sodium complex (NaX), and barium complex (BaX+) are also monomeric in methanol solution. These results are in contrast to the Na2X2 dimer and the BaX2-H20 dimer observed in crystals and in nonpolar (cyclohexane and methylene chloride) solutions. Large downfield shifts on complex formation (X- to NaX and BaX+) are detected for protons located on the polar face of the ionophore with their C-H bonds directed towards and proximal to the metal ion. The exchange of lasalocid anion between free (X-) and complexed (BaX+) states in methanol can be monitored from the temperature-dependent line shapes of the proton resonances at superconducting fields. The exchange rates are independent of the reactant concentrations and are characteristic of a rate-determining dissociation of BaX+ in methanol solution with activation parameters delta H++ = 6.5 kcal mol-1 (25 degrees) and delta S++ = -20.0 cal mol-1 degree -1 (1 cal = 4.184 J). The rate constants for dissociation and formation of BaX+ complex in methanol, 25 degrees, are 5.2 X 10(3) sec-1 and 1.5 X 10(10) M-1 sec-1, respectively. These studies were extended to derive the activation parameters for the exchange of lasalocid anion between BaX+ and NaX and between BaX+ and HX in methanol, while the exchange among HX, X-, and NaX is too rapid to be monitored on the time scale of nuclear magnetic resonance.