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PubMed2002

Diphosphanylketenimines: new reagents for the synthesis of unique phosphorus heterocycles.

Two consecutive [3+2] cycloaddition reactions of the diphosphanylketenimine (PPh(2))(2)C[double bond]C[double bond]NPh (3), involving the phosphanyl groups, with two equivalents of the electron-poor alkynes dimethyl acetylenedicarboxylate or methyl acetylenecarboxylate give rise to the formation of the bicyclic 1 lambda(5),3 lambda(5)-diphospholes 5 a,b, which contain a phosphorane unit with five carbon substituents attached to the phosphorus center. Compound 3 undergoes cyclodimerization by crystallization, affording the unsymmetrical dimer 6, which is converted back to 3 by heating in toluene. Compound 6 can be oxidized stepwise on the three trivalent phosphorus atoms by treatment with H(2)O(2) affording 7, 9, and the transient species 10, which are transformed into their corresponding ketenimine monomers either spontaneously (10) or by heating in toluene (7, 9). In this way, the compound (O[double bond]PPh(2))(PPh(2))C[double bond]C[double bond]NPh (8) is quantitatively obtained. Compound 8 readily reacts with the alkynes MeO(2)CC[triple bond]CCO(2)Me and MeO(2)CC[triple bond]CH, and with phenyl isocyanate and ethyl isothiocyanate through regiospecific [3+2] cycloaddition processes furnishing several lambda(5)-phosphole and lambda(5)-azaphosphole derivatives. Finally, the reaction of 8 with N-methylpropargylamine yields the new 2,3-dihydro-1,4-lambda(5)-azaphosphinine 15 through a cycloaddition process involving two functional groups from each molecule.

Journal Article↗
PubMed2002

Microstructural dependence on relevant physical-mechanical properties on SiO2-Na2O-CaO-P2O5 biological glasses.

Bioactive glasses of the system SiO2-Na2O-CaO-P2O5 have been prepared by the normal melting and annealing technique. The elastic moduli, attenuation, Vickers hardness, fracture toughness and fracture surface energy have been obtained using the known method at room temperature. The temperature dependence of elastic moduli and attenuation measurements have been extended over a wide range of temperature from 150 to 500 K. The SiO2 content dependence of velocities, attenuation, elastic moduli, and other parameters show an interesting observation at 45 wt% of SiO2 by exhibiting an anomalous behaviour. A linear relation is developed for Tg, which explores the influence of Na2O on SiO2-Na2O-CaO-P2O5 bioactive glasses. The measured hardness, fracture toughness and fracture surface energy show a linear relation with Young's modulus. It is also interesting to note that the observed results are functions of polymerisation and the number of non-bridging oxygens (NBO) prevailing in the network with change in SiO2 content. The temperature dependence of velocities, attenuation and elastic moduli show the existence of softening in the glass network structure as temperature increases.

Biocompatible Materials↗
PubMed2006

Trapping of hemiquinone radicals at Mo and P sites by phosphide-bridged dimolybdenum species: chemistry of complexes [Mo2(eta5-C5H5)2(OC6H4OH)(mu-PR2)(CO)4] and [Mo2(eta5-C5H5)2{mu-PR(OC6H4OH)}(CO)4]- (R = Cy, Ph).

The phosphide-bridged dimolybdenum complexes (H-DBU)[Mo2Cp2(mu-PR2)(CO)4] (R= Cy, Ph; DBU = 1,8-diazabicyclo[5.4.0.]undec-7-ene) react with p-benzoquinone to give the hemiquinone complexes [Mo(2)Cp2(OC6H4OH)(mu-PR2)(CO)4]. The latter experience facile homolytic cleavage of the corresponding Mo-O bonds and react readily at room temperature with HSPh or S2Ph2 to give the thiolate complexes [Mo2Cp2(mu-PCy2)(mu-SPh)(CO)4] or [Mo2Cp2(mu-PR2)(mu-SPh)(CO)2]. In contrast, PRH-bridged substrates experience overall insertion of quinone into the P-H bond to give the anionic compounds (H-DBU)[Mo(2)Cp2{mu-PR(OC6H4OH)}(CO)4], which upon acidification yield the corresponding neutral hydrides. The cyclohexyl anion experiences rapid nucleophilic displacement of the hemiquinone group by different anions ER- (ER = OH, OMe, OC4H5, OPh, SPh) to give novel anionic compounds (H-DBU)[Mo2Cp2{mu-PCy(ER)}(CO)4], which upon acidification yield the corresponding neutral hydrides. The structure of four of these hydride complexes [PPh(OC6H4OH), PCy(OH), PCy(OMe), and PCy(OPh) bridges] was determined by X-ray diffraction methods and confirmed the presence of cis and trans isomers in several of these complexes. In addition, it was found that the hydroxyphosphide anion [Mo2Cp2{mu-PCy(OH)}(CO)4]- displays in solution an unprecedented tautomeric equilibrium with its hydride-oxophosphinidene isomer [Mo2Cp2(mu-H){mu-PCy(O)}(CO)4]-.

Anions↗
PubMed1992

Quisqualic acid analogues: synthesis of beta-heterocyclic 2-aminopropanoic acid derivatives and their activity at a novel quisqualate-sensitized site.

Hippocampal CA1 pyramidal cell neurons are sensitized over 30-fold to depolarization by L-2-amino-4-phosphonobutanoic acid (L-AP4) following exposure to L-quisqualic acid. This phenomenon has been termed the QUIS effect. In the present study several novel L-quisqualic acid analogues have been synthesized and tested for their interaction with the different components of the QUIS-effect system. Replacement of the oxadiazolidinedione ring of L-quisqualic acid with several other types of heterocyclic rings yielded the following quisqualic acid analogues: maleimide 2, N-methylmaleimide 3, N-(carboxymethyl)maleimide 4, succinimides 5A and 5B, and imidazolidinedione 6. None of these analogues were able to mimic the effects of L-quisqualic acid and sensitize hippocampal CA1 neurons to depolarization by L-AP4. Also, unlike L-serine O-sulfate, L-homocysteinesulfinic acid, or L-alpha-aminoadipic acid, none of the analogues were able to preblock or reverse the QUIS effect. However, when the IC50 values for inhibition of the CA1 synaptic field potential of analogues 2-6 were determined both before and after hippocampal slices were exposed to L-quisqualic acid, the IC50 values of analogues 3 and 4 were found to decrease more than 7-fold. Thus, these two compounds behave like L-AP4 rather than L-quisqualic acid in this system in that they exhibit increased potencies in slices that have been pretreated with L-quisqualic acid even though they cannot themselves induce this sensitization. Compounds 3 and 4, therefore, represent the first non-phosphorus-containing compounds to which hippocampal neurons become sensitized following exposure to L-quisqualic acid. No change in the IC50 values was observed for 5A or 5B. Analogues 2 and 6, on the other hand, displayed a high potency for inhibition of the evoked field potential even prior to treatment of the slices with L-quisqualic acid.

Aminobutyrates↗
PubMed1994

[Attempt at evaluation of alfacalcidol administered by an oral pulsatile method to chronically dialysed patients with advanced secondary hyperparathyroidism].

One of the basic complications of chronic renal failure is secondary hyperparathyroidism. The purpose of the work was an attempt at the assessment of the effectiveness of pulsating dosage of alfacalcidol as compared to daily dosage. Ten chronically dialysed patients were given for four months alfacalcidol in the mean dose 1 mcg daily, with simultaneous administration of calcium preparations and phosphorus-binding compounds. Every month the serum concentrations of total calcium and phosphorus were determined together with alkaline phosphatase activity. For another four months the same group of patients received alfacalcidol in pulsating way in dose of 0.1 mcg/kg body weight, once weekly. As compared with the period of treatment with daily doses of alfacalcidol, the change of treatment method to pulsating one caused a significant increase of calcemia as well as an evident decrease of alkaline phosphatase activity with a marked increase of phosphatemia.

Administration, Oral↗
PubMedDate not supplied

Solid-state 29Si, 113Cd, 119Sn, and 31P NMR studies of II-IV-P2 semiconductors.

Solid-state 29Si, 113Cd, 119Sn, and 31P MAS NMR spectra are reported on a series of II-IV-P2 compounds. In favorable cases (e.g., high degree of crystallinity, low concentration of unpaired electrons), well-defined spectra, with sharp lines for each specific nearest-neighbor configuration, are observed; in such cases, expected J coupling patterns are also seen. High-resolution solid-state NMR studies of this type provide useful information on structure (disorder), doping, and electron-mediated coupling in semiconductor systems.

Cadmium↗
PubMed1994

Influence of colorants on crystallization and mechanical properties of lithia-based glass-ceramics.

OBJECTIVES: The objective of the present study was to test the hypothesis that colorants such as AgNO3 and FeCl3 act as conucleating agents with P2O5 in the Li2O-Al2O3-CaO-SiO2 system and that the addition of either colorant and P2O5 produces a greater effect on crystallization and selected mechanical properties than the use of P2O5 alone. METHODS: Microstructural effects were observed by SEM and optical microscopy. Mechanical properties were determined to monitor the effects of structural changes after crystallization. These include controlled-flaw flexure strength, fracture toughness (KIC), and Vickers hardness (VHN). RESULTS: Based on a glass composition of 27.84 mol% Li2O, 2.45 mol% Al2O3, 5.88 mol% CaO, and 63.84 mol% SiO2 (LACS), the mechanical properties of LACS glass-ceramics were influenced by P2O5, the colorant type, and the colorant concentration. The mean strength of the glass-ceramic disks without P2O5 increased with AgNO3 concentration to a peak value of 188 MPa at a concentration of 0.78 mmol%. The maximum value of controlled-flaw flexure strength increased from 120 MPa for one of the FeCl3 groups to 188 MPa for one of the AgNO3 groups. The maximum fracture toughness of glass-ceramic disks without P2O5 (2.45 MPa.m1/2) was associated with a AgNO3 concentration of 0.58 mmol%. This value was significantly greater (p < 0.05) than that of the corresponding group (1.90 MPa.m1/2) which also contained P2O5. There was no significant change in KIC of glass-ceramic specimens containing P2O5 as the AgNO3 concentration increased. The increase in controlled-flaw flexure strength and fracture toughness of specimen groups containing 0.58 to 0.78 mmol% AgNO3 support its use as a colorant and as a nucleating agent in LACS glass-ceramics. SIGNIFICANCE: The development of tougher, higher strength glass-ceramics can be controlled by the use of colorants that are also effective as nucleating agents. Although certain colorants are believed to act synergistically when used in combination with known nucleating agents to enhance the fracture toughness of glass-ceramics, this effect was not observed in this study for the combined use of AgNO3 and the classical nucleating agent, P2O5. In fact, the colorant used in this study (AgNO3) was more effective than P2O5 as a nucleating agent for lithia-based glass-ceramics.

Ceramics↗
PubMed1984

Phosphonate Utilization by the Glyphosate-Degrading Pseudomonas sp. Strain PG2982.

The glyphosate-degrading Pseudomonas sp. strain PG2982 was found to utilize each of 10 organophosphonate compounds as a sole phosphorus source. Representative compounds tested included alkylphosphonates, 1-amino-substituted alkylphosphonates, amino-terminal phosphonates, and an arylphosphonate. This report demonstrates that PG2982 is capable of utilizing a wider range of structurally different organophosphonate compounds than any organism described to date.

Journal Article↗
PubMed1984

Synthesis and properties of N-, O-, and S-phospho derivatives of amino acids, peptides, and proteins.

The literature on chemical (i.e., nonenzymic) phosphorylation of amino acids, peptides, and proteins is reviewed through 1982. The review covers synthetic methods, chemical reactions, and physical properties, with emphasis on the techniques used for separation and characterization of the products. Synthetic methods are classified by reagent rather than product, and are illustrated by experimental procedures for the most important methods. Chemical reactions are classified into four groups depending on whether the reaction site is the phospho group, the amino group, the carboxyl group, or in the case of serine the hydroxyl group. Physical data are given for all of the known N-, O-, and S-phospho derivatives of the amino acids, peptides, and proteins, within certain limitations, and are discussed in detail in the section on physical properties. Emphasis is given to the techniques used for separation of the products, such as chromatography and electrophoresis, and for characterization of the products, particularly spectroscopy. Medical and other uses of the products are mentioned.

Aldehydes↗
PubMedDate not supplied

Determination of iron to phosphorus ratios of iron storage compounds in patients with iron overload: a chemical and electron probe X-ray microanalysis.

The amounts of phosphorus and iron in various isolated ferritin preparations were investigated by: chemical analysis on ferritin samples and electron probe X-ray microanalysis on ferritin particles from the same preparations. A high correlation was found between iron to phosphorus ratios obtained by both methods. Further investigation by electron probe X-ray microanalysis on lysosomes of hepatic cells of patients with idiopathic and secondary hemochromatosis revealed lysosomal iron to phosphorus ratios which were very similar in all parenchymal cells but different from ratios obtained in Kupffer cells. Lysosomal iron to phosphorus ratios in hepatocytes did not change after intensive phlebotomy treatment. It is postulated therefore that, during phlebotomy, iron and phosphorus are concomitantly lost from the hepatic lysosomes.

Bloodletting↗
PubMed1997

Chemical durability of Dicor and lithia-based glass-ceramics.

OBJECTIVES: The aim of this study was to analyze the effect of a nucleation agent (P2O5) and a colorant/nucleation agent (AgNO3) on the chemical durability of Li2O-Al2O3-CaO-SiO2(LACS) glass-ceramics in 4% HAc solution, deionized-distilled water, and in pH buffer solutions of pH 1, pH 9, and pH 11. METHODS: Glass powder [27.8 mol% Li2O, 2.5% Al2O3, 5.9% CaO, and 63.8% SiO2(LACS)] was melted, poured into a cylindrical graphite mold (16 mm diameter), cooled, cut into 2.2 mm thick disks, polished through 1200 grit SiC, nucleated at 510 degrees C for 3 h, and crystallized at 650 degrees C for 6 h. Dynamic corrosion tests of LACS glass-ceramic, LACS glass-ceramic containing 1.0 mol% P2O5 (LACSP), LACS glass-ceramic containing 0.78 mmol% AgNO3(LACSAg), and Dicor control specimens were performed in a shaker-bath unit at 80 degrees C at a shaker speed of 30 cycles/min for periods of up to 15 d. Differences in mean weight loss and ionic concentration were analyzed for statistical significance (p = 0.05) using ANOVA and the Tukey's Studentized Range Test. RESULTS: The mean weight loss over 15 d in 4% HAc increased in the following order: LACS (0.21 +/- 0.02 mg/cm2), LACSAg (0.25 +/- 0.05 mg/ cm2), and Dicor (0.27 +/- 0.05 mg/cm2). The differences in mean values were not statistically significant (p > 0.05). The amounts of Li+ leached in 32 mL of pH1 and pH11 buffer solutions were 3.1 +/- 0.3 microgram/cm2/mL and 243 +/- 49.0 micrograms/cm2/mL, respectively, for the LACS group, and 3.0 +/- 0.6 microgram/cm2/mL and 166 +/- 28.0 micrograms/cm2/mL for the LACSAg group. The differences in mean values are not statistically significant (p > 0.05). The high chemical durability in acidic environments of LACS glass-ceramics without P2O5 and their decreased durability at pH values of 9 and above were confirmed by SEM observations of the exposed surfaces. SIGNIFICANCE: The weight loss for the three glass-ceramic systems was highest in pH 11 buffer solution, which represents an unlikely in vivo environment. From a toxicological viewpoint, the maximum amount of Li+ released from 28 fully dissolved crowns of LACS glass-ceramic at a temperature of 80 degrees C (which is greater than any temperature experienced in the oral cavity) is approximately 1.2 mg; this amount appears to be below the daily limit of 2 mg allowable from food sources.

Aluminum Silicates↗