Filiation biochimique des acides phénoliques produits parPenicillium brevi-compactum

Résumé LeP. brevi-compactum produit onze substances phénoliques différentes: l'acide mycophénolique, les acides phénoliques C₁₀H₁₀O₅, C₁₀H₁₀O₆, C₁₀H₁₀O₇ et C₈H₆O₆ et les substances phénoliques non identifiées désignées par les chiffres VI, VII, VIII, IX, X et XI. L'acide mycophénolique et les substances X et XI qui en dérivent, sont synthétisés par la moisissure suivant un processus plus complexe que les autres substances phénoliques et sans rapport direct avec lui. Ces dernières dérivent les unes des autres par une série de transformations dont certaines sont réversibles. Il semble que les substances VI et VII soient des intermédiaires entre C₁₀H₁₀O₇ et C₈H₆O₆, tandis que les substances VIII et IX seraient des produits de réduction de C₁₀H₁₀O₅.

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Summary P. brevi-compactum produces eleven phenolic different substances, mycophenolic acid, phenolic acids C₁₀H₁₀O₅, C₁₀H₁₀O₆, C₁₀H₁₀O₇ and C₈H₆O₆, and the non-identified substances designed by the numbers VI, VII, VIII, IX, X and XI. Mycophenolic acid and its derivates X and XI are synthesized by the mould according to a process more complex than the other phenolic substances and have no direct connection with them. The latter derive the one from the other, in a succession of transformations some of which are reversible. It seems that the substances VI and III are intermediaries between C₁₀H₁₀O₇ and C₈H₆O₆, the substances VIII and IX being produced by reduction of C₁₀H₁₀O₅.

     

Synthesis and structure of a lead(II)-citrate: {Na(H2O)3}[Pb5(C6H5O7)3(C6H6O7)(H2O)3]·9.5H2O

The reaction of lead(II) nitrate with trisodium citrate Na₃(C₆H₅O₇) in a 1:22.5 ratio at pH 4.8 provides crystals of {Na(H₂O)₃}[Pb₅(H₂O)₃(C₆H₅O₇)₃(C₆H₆O₇)]·9.5H₂O (1). The structure of 1 is two-dimensional and exhibits five distinct Pb(II) sites and four different modes of citrate bonding. The five lead sites all display hemidirected coordination geometries, that is, irregular distribution of neighboring oxygen atoms resulting in obvious gaps in the coordination spheres. Consequently, the lead coordination geometries exhibit proximal bonding to a number of oxygen donors, as well as distal interactions with nearest neighbors. The coordination numbers vary from 8 to 10, with ‘5+3’, ‘5+4’, ‘6+4’ and ‘7+3’ coordination modes where the first number refers to the proximal ligands and the second to the distal set. The four crystallographically distinct citrate groups include three with deprotonated carboxylate groups (C₆H₅O₇)³⁻ and one with a single protonated carboxyl group (C₆H₆O₇)². The citrate ligands bridge 3, 5, 7 and 7 lead sites. Three of the citrate groups exhibit tridentate chelation coordination to a lead site through two carboxylate oxygen donors and the hydroxyl groups. One citrate group projects an uncoordinated -OH group and a pendant protonated carboxyl group into the interlamellar domain. This latter carboxyl group coordinates to a sodium cation, which exhibits five coordinate geometry defined by three aqua ligands and the carbonyl oxygen of the -CO₂H groups in the basal plane and a citrate -OH donor in the apical position.     

Synthesis, crystal structure and vibrational spectroscopy of a novel mixed ligands Ni(II) pentaborate: [Ni(C4H10N2)(C2H8N2)2][B5O6(OH)4]2

A novel organic-inorganic hybrid pentaborate [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂][B₅O₆(OH)₄]₂ has been synthesized by hydrothermal reaction and characterized by FT-IR, Raman spectroscopy, elemental analyses and DTA-TGA. Its crystal structure was determined from single crystal X-ray diffraction. The structure consists of isolated polyborate anion [B₅O₆(OH)₄]⁻ and nickel complex cation of [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺, in which the two kinds of ligands come from the decomposition of triethylenetriamine material. The [B₅O₆(OH)₄]⁻ units are connected to one another through hydrogen bonds, forming a three-dimensional framework with large channel along the a and c axes, in which the templating [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺ cations are located. The assignments of the record FT-IR absorption frequencies and Raman shifts were given.     

An aluminoborate cluster [AlB12O14(OH)12]: Synthesis and structure of [C5H6N][AlB12O14(OH)12]

A new aluminoborate, [C₅H₆N][AlB₁₂O₁₄(OH)₁₂], has been hydrothermally synthesized at 200 °C. The single-crystal diffraction study reveals that it crystallizes in space group C2/c. It consists of aluminoborate clusters [AlB₁₂O₁₄(OH)₁₂]⁻ and counterions [C₅H₆N]⁺. The aluminoborate cluster contains an Al(OH)₆ octahedron as a core that is capped by two raft-like polyborate units [B₆O₇(OH)₆]. These clusters are further interlinked by extensive hydrogen bonding to form a three-dimensional (3D) network, containing large channels along the b-axis, in which the [C₅H₆N]⁺ cations are located.     

Studies on Polyoxins,Antifungal Antibiotics

Seven additional components, polyoxins C, D, E, F, G, H and I were isolated from polyoxin complex. They have molecular formulae corresponding to C₁₁H₁₅N₃O₈, C₁₇H₂₃N₅O₁₄, C₁₇H₂₃N₅O₁₃, C₂₃H₃₀N₆O₁₅, C₁₇H₂₅N₅O₁₂, C₂₃H₃₂N₆O₁₃ and C₁₉H₂₄N₄O₁₂, respectively. These polyoxins except inactive polyoxins C and I were highly active against various kinds of phytopathogenic fungi. The close structural similarity among them including polyoxins A and B is also discussed.     

Infrared and raman spectra of metal 1,2,4,5-benzenetetracarboxylates: Evidence for very short,strong hydrogen bonds

Salts of 1,2,4,5-benzenetetracarboxylic acid with copper, aluminum, ammonium, cobalt(II), thallium(I), tin(II), uranyl ion, zinc, manganese, iron(II), nickel, potassium and sodium have been prepared and characterized by their IR spectra. The salts of aluminum, ammonium, thallium(I), tin(II), zinc, iron(II), nickel, potassium and sodium had not been reported before with adequate characterization. Raman spectra of selected compounds also aided structural interpretation. The IR spectra of Na₂C₁₀H₄O₈·2H₂O, Fe(C₁₀H₅O₈)₂·12H₂O, Zn(C₁₀H₅O₈)₂·12H₂O, Ni(C₁₀H₅O₈)₂·12H₂O, (NH₄)₃C₁₀H₃O₈·H₂O and CoC₁₀H₄O₈·6H₂O indicate very short, strong hydrogen bonds in these compounds. The IR and Raman spectra can be used to determine the mode of coordination (if any) of the carboxylate groups of 1,2,4,5- benzenetetracarboxylate to metal ions.     

The Effect of Cyclopropane on Ion Uptake and Protoplasmic Streaming in Barley Roots

Increasing concentrations of cyclopropane up to about 95 % C₃H₆—5 % O₂ caused an increasing inhibition of uptake by excised barley roots from KC1 solution, much more so for Cl than K. No inhibition of K uptake from K₂SO₄ occurred under similar conditions. It is suggested that the small decrease in K uptake from KC1 is related to the large decrease in Cl uptake and that C₃H₆ primarily inhibits Cl uptake with little or no effect on K uptake. Time curves of uptake in 80 % C₃H₆ 20 % O₂ revealed no indication of cumulative injury in either KC1 or K₂SO₄ for periods up to 3 hours. The amount of organic acid production associated with K uptake from K₂SO₄ was about the same in 80 % C₃H_g— 20 % O₂ as in air. Oxygen consumption in K₂SO₄ was unaffected by the gas mixture and only slightly affected in KC1. Protoplasmic streaming in epidermal cells was rapidly stopped at C₃H₆ concentrations of 20 % or higher. In 80 % C₃H₆–20 % O₂ the effect on streaming was confined mostly to the outer two or three layers of root cells. A connection between the cessation of streaming and the inhibition of Cl uptake appeared to exist but very little if any relationship between streaming and K uptake was observed.     

A new mixed-ligand copper pentaborate with square-like, rectangle-like and ellipse-like channels formed via hydrogen bonds

A new mixed-ligand copper pentaborate, [Cu(en)₂(C₅H₉NO)][B₅O₆(OH)₄]₂·C₅H₉NO (en is ethylenediamine) (1), with novel framework has been synthesized under mild solvothermal condition and characterized by FT-IR, elemental analyses, powder X-ray diffraction and TG-DTA. The structure consists of isolated polyborate anion [B₅O₆(OH)₄]⁻, copper complex cation [Cu(en)₂(C₅H₉NO)]⁺ and one C₅H₉NO molecule. The [B₅O₆(OH)₄]⁻ units are connected to one another through hydrogen bonds to form an interesting three-dimensional (3D) supramolecular framework with alternate square-like channels and rectangle-like channels along the c-axis as well as ellipse-like channels with 16-membered boron rings along the a-axis which are the largest channels in the pentaborate reported so far. The copper complex cation contains two kinds of ligands, en and C₅H₉NO, forming a square pyramid with an O atom as the vertex.     

Hatch opening and closing on oxygenation and deoxygenation of C60 bathysphere

The structures and stabilities of C₆₀O_n, where n=1-6, 9, have been calculated using the AM1 Hamiltonian and the program mopac 6.0, and by the density functional technique B3LYP/6-31G* at the AM1 geometry using Gaussian 98. Modes of oxygen addition considered were ethers, epoxides, ketones and ketenes. It is confirmed that in C₆₀O a carbon-carbon bond on a pent-hex edge is replaced by an ether linkage. For higher levels of oxygen addition the replacement of a carbon-carbon bond by two ketone groups becomes important. Particularly stable structures are formed if the additions are on the same, or adjacent, C₆ rings of the C₆₀ structure where the oxygen atoms cooperate in opening up large holes in the molecule. Molecules of greatest stability have a mixture of ether oxygen atoms on pent-hex edges and diketone additions on hex-hex edges. A particularly important stable structure is the mixed ether/ketone isomer of C₆₀O₆ in which a hinged C₅O₂ hatch lid containing two ketone oxygen atoms is opened revealing a hatch 4-5 Å in diameter. An even larger hole of approximately 6 Å in diameter is opened up in a particularly stable isomer of C₆₀O₉ which contains three ether and six ketone groups. Removal of the oxygen atoms from these structures and reoptimisation leads to hatch closing and C₆₀ is reformed.     

95Mo NMR studies of complexes containing the Mo2O52+ core and crystal structure of Mo2O5[SC6H4NHCH2C5H4N]2(C3H7NO)3

The crystal structure of Mo₂O₅[SC₆H₄NHCH₂C₅H₄N]₂(C₃N₇NO)₃ is reported and seen to consist of a single oxo-bridged species with each Mo atom bonded to cis dioxo groups and the nitrogen atoms and thiolate group of the tridentate ligand. ⁹⁵Mo NMR spectra of this and three related complexes are presented and attempts made to interpret them in terms of their crystal structures.     

Studies on Mitomycins,Carcinostatic Antibiotics

Mitomycin A (C₁₆H₁₉O₆N₃) and mitomycin C (C₁₅H₁₈O₅N₄) are pigments which have the quinoid structure. When treated with aqueous ammonia, mitomycin A is converted to mitomycin C. Acid hydrolysis of mitomycin C gave three degradation products, namely, C₁₄H₁₅O₅N₄, C₁₄H₁₅O₆N₃ and C₁₃H₁₄O₅N₂. Acetylation with acetic anhydride and pyridine and methylation with methyl iodide gave monoacetyl and monomethyl derivatives of mitomycin C respectively, though diacetate of demethyl derivatives were obtained when boiled with acetic anhydride.     

Hybrid materials composed of tetravanadate motifs: Synthesis, structure and magnetic properties of the open framework structure solids [{M(C5H5N)4}2]V4O12 (M = Cu, Co)

Two new inorganic-organic hybrid materials - [{M(C₅H₅N)₄}₂]V₄O₁₂ (M = Cu, 1; M = Co, 2) have been synthesized and characterized by spectroscopic methods, X-ray powder diffraction, thermogravimetry, magnetometry and complete single crystal structure analysis. The structures of 1-2 are comprised of layers containing centrosymmetric {V₄O₁₂} rings connected to {M(C₅H₅N)₄} units by V-O-M bridges (M = Cu, 1; M = Co, 2). The layers are parallel to the (1 0 1) crystal planes and there are pyridine stacking interactions between layers. The effective magnetic moment, μ_eff, values for 1 and 2 are 1.9 μ_B and 3.9 μ_B, respectively, indicating some orbital contributions in each case. Both compounds exhibit Curie-Weiss magnetic behavior over the entire range above the critical temperature.     

MOLECULAR STRUCTURE OF PLANT FIBERS DETERMINED BY X-RAYS

It has been shown that the wall of the plant fiber is probably built up of unit groups of atoms which have assumed the form of a space lattice. The elementary cell of the lattice is an orthorhombic structure with the dimensions 6.10 x 5.40 x 10.30 Å.u., and contains two unit groups equal in size to two C₆H₁₀O₅ groups. The crystallographic unit cell would contain 4 of these elementary cells and would be represented by Fig. 9 rather than by Fig. 3. The groups of atoms, C₆H₁₀O₅, are arranged in parallel chains running lengthwise of the fiber. In each chain the odd numbered groups have a different orientation from the even numbered. The chains, parallel to one another are spaced 6.10 Å.u. in one direction and 5.40 Å.u. at right angles to that. In these two directions the odd numbered chains also would have a different orientation from the even numbered. On account of the cylindrical shape of the fiber, the elementary cells are arranged in the form of concentric cylinders or layers. The dimensions of the fibers are such that the fiber wall is about 40,000 elementary cells in thickness, or in other words, the fiber is composed of that many concentric layers. If it could be magnified sufficiently, a cross-section of a fiber would show the end view of each cylinder as a dotted circle. The dots, representing the unit groups of atoms, would have considerable uniformity of spacing in both the tangential and the radial directions, 6.10 Å.u. in one and 5.40 Å.u. in the other. The structure could not be as rigidly exact as might be inferred, since the wall is deposited more or less rhythmically during a period of several days or weeks* in which adjustments in the arrangement of the unit groups undoubtedly occur. It is common knowledge that the fibers, under the microscope, rarely appear as true circles on cross-section; usually they appear as irregular, many-sided polygons and the wall thickness is normally uneven. For our purpose it is simpler to think of the fiber as composed of concentric cylinders with diameters so large in proportion to the size of the unit groups that in relatively large segments they closely approach the parallelism of the planes of a rectangular lattice, sufficiently close to be capable of producing diffraction patterns. Although these conclusions seem to be in agreement with the diffraction patterns obtained from various positions of a bundle of approximately parallel fibers, the fact must not be overlooked that the structure cannot be proved with as great certainty as can the structure of a well formed crystal. The very nature of the fiber, its cylindrical shape, and the many internal adjustments which must take place, militate against a clean-cut demonstration. Models, made more or less to scale, were used in working out this structure. The unit group was constructed according to Irvine''s suggestion that all the groups are glucose residues. An intensive study is now under way in which an attempt is being made to bring the models into agreement with the chemical and physical properties of the cellulose fibers and with the diffraction patterns. A report on that part of the work will soon be submitted for publication.     

Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

Results are presented from experimental studies of decomposition of toluene (C₆H₅CH₃) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C₆H₅CH₃ removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N₂: O₂: H₂O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C₆H₅CH₃ decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C₆H₅CH₃ is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.     

Crystal structure at 87 K of sodium α-l-guluronate dihydrate

X-Ray data collected at 87 K showed crystals of sodium α-l-guluronate dihydrate (C₆H₉O₇Na · 2 H₂O) to be orthorhombic, P2₁2₁2₁ with a = 7.591(2), b = 18.884(5), c = 6.842(2) Å, and Z = 4. The structure was solved by direct methods, and full-matrix least-squares refinement based on 1587 F_o yielded R = 0.043 and R_w = 0.033. The structure analysis indicates partial anomeric disorder with α:β ～90:10. The guluronate ring has the ¹C₄(l) conformation. Sodium binds two translation-equivalent guluronate units and one water molecule in a primary five-fold coordination. The complexing oxygen functions, which include all axial hydroxyl groups and one carboxylate oxygen atom in the guluronate ring, describe a distorted trigonal bipyramid. A prominent feature of the crystal structure is the stacks of sodium atoms and guluronate residues in alternating sequence along the c axis. The stacks are held together by an intricate system of hydrogen bonds involving all oxygen atoms in the structure. The water molecules play an important role in this system both as hydrogen donors and acceptors.     

Atomic-scale structure of nanocrystals by the atomic pair distribution function technique

The approach of the atomic pair distribution function (PDF) technique to determine the atomic-scale structure of nanocrystalline materials is introduced and illustrated with results of studies on V₂O₅ nanotubes and clusters of Cs atoms intercalated inside the pores of the zeolite ITQ-4. We find that V₂O₅ nanotubes are built of double layers of V-O₅ and V-O₄ units. Inside the channels in ITQ-4 Cs atoms are found to assemble in short-range ordered zigzag chains.     

Delving into the complex picture of Ti(IV)-citrate speciation in aqueous media: Synthetic, structural, and electrochemical considerations in mononuclear Ti(IV) complexes containing variably deprotonated citrate ligands

The aqueous reaction of TiCl₄ with citric acid at pH ∼ 4 (KOH), led to the surprising isolation of a species assembly K₃[Ti(C₆H₆O₇)₂(C₆H₅O₇)] · K₄[Ti(C₆H₅O₇)₂(C₆H₆O₇)] · 10H₂O (1). The same system at pH ∼ 3 (neocuproine), led to the crystalline material (C₁₄H₁₃N₂)₂[Ti(C₆H₆O₇)₃] · 5H₂O (2), while at pH 5.0 (NaOH), afforded Na₃[Ti(C₆H₆O₇)₂(C₆H₅O₇)] · 9H₂O (3). Analytical, spectroscopic and structural characterization of 1, 2 and 3 revealed their distinct nature exemplified by mononuclear complexes bearing variably deprotonated citrates bound to Ti(IV). Solid-state ¹³C MAS NMR spectroscopy in concert with solution ¹³C and ¹H NMR on 3 provided ample evidence for the existence of bound citrates of distinct coordination mode to the metal ion. Cyclic voltammetry defined the electrochemical signature of complex 2, thereby projecting the physicochemical profile of the species formulated by the aforementioned properties. Comparison of cyclic voltammetric data on available discrete Ti(IV)-citrate species depicts the electrochemical profile and an E_1/2 value trend of the species in that binary system’s aqueous speciation, further substantiating the redox behavior of mononuclear Ti(IV)-citrate species in a pH-sensitive fashion. Collectively, the well-defined discrete species in 1-3 reflect and corroborate a synthetically challenging yet complex pH-specific picture of the aqueous Ti(IV) chemistry with the physiological citric acid, and shed light on the pH-dependent speciation in the binary Ti(IV)-citrate system.     

Synthesis and magnetic characterization of Ln(III) complexes with 4,4′-bipyridine and crotonato as bridging ligands

The crystal structure and magnetic characterization of an isostructural series of general formula {[Ln(crot)₃(H₂O)(bpy)_1/2]₂}_n (crot, crotonate (C₄H₅O₂); bpy, 4,4′-bipyridine (C₁₀H₈N₂); Ln, Nd, Gd, Ho, Er, Y) is presented. The ninefold Ln coordination polyhedra form dimeric entities that are connected throughout the bpy units into infinite polymeric chains. All (but the yttrium) reported compounds present a weak antiferromagnetic interaction connecting metal centres.     

Coordination properties of α-hydroxy carboxylic acids. Part I. Binuclear niobium (V) complex acids and some salts

The conditions of dissolution of freshly precipitated niobium (V) oxide in α-hydroxy carboxylic acids glycolic, lactic, malic and tartaric were investigated. The dissolution is a function of the molar ratio α-hydroxy carboxylic acid/hydrated niobium(V) oxide, pH of the solution, temperature and time. From solutions of α-hydroxy monocarboxylic acids at 2 < pH < 3 the binuclear complexes H₃O[Nb₂O₄(C₂H₂O₃)(C₂H₃O₃)]·H₂O and H₃O[Nb₂O₄(C₃H₄O₃)(C₃H₅O₃)]·H₂O were isolated. Colourless, poorly-crystalline complexes are 1:1 electrolytes and, according to i.r. spectral evidence, the binuclearity in their structures is achieved through oxygen bridges. With α-hydroxy dicarboxylic acids crystalline M[Nb₂O₃(C₄H₃O₅)(C₄H₄O₅)]·nH₂O and poorly crystalline complexes, M₂[Nb₂O₂(C₄H₂O₆)₂]·nH₂O, M = H₃O⁺, NH₄⁺ were prepared as 1:1 electrolytes for the former and 1:2 electrolytes for the latter. Analytical, spectral, conductometric and potentiometric titration data give evidence for binuclear malatoniobate(V) and tartratoniobate(V) anions with bridging complex-forming agents.     

XRD and DFT-modelized structures of a pteridine-2,4(1H,3H)-dithione/N,N′-dimethylformamide H-bonded cluster (2:2). MO study of the coordination ability

The title compound, C₆H₄N₄S₂·C₃H₇NO, crystallizes in the monoclinic space group C 2/c with a = 26.673(5), b = 5.397(1), c = 16.522(3) Å, β = 95.49(3)°, Z = 8, R = 0.0461 for 1891 reflections with I > 2σ(I) and 174 parameters (4 restraints). Single pteridine-2,4(1 H,3 H)-dithione and dimethylformamide molecules are packed via N-H···O and N-H···N hydrogen bonds into centrosymmetric clusters containing two molecules of each class; these are roughly planar and placed into two different sets of planes -both containing the [−1,0,2] direction- mutually angled by 77.8°. Despite the distance between two neighbor planes in each set is ca. 3.4 Å, the analysis of π,π-stacking interactions shows too large slippage distance between aromatic rings from contiguous planes. Additional σ-π interactions between S2, S4 and O1S atoms and pyrazine or pyrimidine rings from adjacent molecules are present. The structure for the cluster [DTLM-DMF]₂ has been simulated by using the density functionals B1B95 (6-31 G(d) and 6-31+G(d) basis sets) and M06-2X (6-31 G(d) basis set). As a result, the M06-2X/6-31 G(d) approach provides the best agreement with the experimental XRD data. For a better evaluation of the intermolecular interactions, the superposition of two dimeric adducts [DTLM-DMF]₂ has been modelized. The binding capability of DTLM ligand was simulated on systems containing two metal-binding modes to palladium (N5-S4 and N1-S2) with different chelate size. The analysis of the frontier orbitals points out that the link with the metallic centers will take place through the sulfur atoms.