Syntheses, structure, and a Mossbauer and magnetic study of Ba4Fe2I5S4

in Inorganic Chemistry (2008), 47(1), 94-100

The compound Ba4Fe2I5S4 has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, and U with BaI2 as a flux. A more rational synthesis was also found; however, the presence of U ... [more ▼]

The compound Ba4Fe2I5S4 has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, and U with BaI2 as a flux. A more rational synthesis was also found; however, the presence of U appears to be essential for the formation of single crystals suitable for X-ray diffraction studies. Ba4Fe2I5S4 crystallizes in a new structure type with two formula units in space group 14/m of the tetragonal system. The structure consists of a Ba-I network penetrated by (1)(infinity) [Fe2S4] chains. Each Fe atom, which is located on a site with 4 symmetry, is tetrahedrally coordinated to four S atoms. The FeS4 tetrahedra edge-share to form linear (1)(infinity)[Fe2S4] chains in the [001] direction. The Fe-Fe interatomic distance in these chains is 2.5630(4) angstrom, only about 3 % longer than the shortest Fe-Fe distance in alpha-Fe metal. Charge balance dictates that the average formal oxidation state of Fe in these chains is +2.5. The Mossbauer spectra obtained at 85 and 270 K comprise a single quadrupole doublet that has hyperfine parameters consistent with an average Fe oxidation state of +2.5. The Mossbauer spectrum obtained at 4.2 K consists of a single magnetic sextet with a small hyperfine field of -15.5 T. This spectrum is also consistent with rapid electron delocalization and an average Fe oxidation state of +2.5. The molar magnetic susceptibility of Ba4Fe2I5S4, obtained between 3.4 and 300 K, qualitatively indicates the presence of weak pseudo-one-dimensional ferromagnetic exchange within a linear chain above 100 K and weak three-dimensional ordering between the chains at lower temperatures. [less ▲]

Synthesis and activity of another seleniated auxin: 2,4-dichlorophenylselenoacetic acid

in Plant Growth Regulation (2003), 40(3), 197-200

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt ... [more ▼]

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt with potassium selenocyanate. 2,4-D-Se has been tested as an auxin in several bioassays including the regeneration of somatic embryos, adventitious root formation and the associated temporary increase of endogenous auxins at the induction phase, and callus formation, and compared with the natural auxin indoleacetic acid (IAA), the classical synthetic auxin(s) naphthaleneacetic acid (NAA) and/or 2,4-dichlorophenoxyacetic acid (2,4-D), and with the synthetic seleniated IAA, 3-(benzo[b] selenienyl) acetic acid, BSAA. These biological assays classified 2,4-D-Se together with BSAA among the most powerful synthetic auxins. The role of selenium is briefly discussed. [less ▲]

Synthesis And Antimicrobial And Toxicological Studies Of Amino-Acid And Peptide Derivatives Of Kanamycin-A And Netilmicin

in Journal of Medicinal Chemistry (1995), 38(23), 4710-9

Amino acid and peptide derivatives of aminoglycosides have been obtained by substitution of the 1-N or 6'-N amino functions of kanamycin A and netilmicin via the temporary complexation of vicinal and ... [more ▼]

Amino acid and peptide derivatives of aminoglycosides have been obtained by substitution of the 1-N or 6'-N amino functions of kanamycin A and netilmicin via the temporary complexation of vicinal and nonvicinal amino and hydroxy functions by copper ion [1-N kanamycin A derivatives: L-Ala (6a), D-Ala (6b), Gly (6c), L-Asp (6d), L-Ala-L-Ala (6e). 6'-N kanamycin A derivatives: L-Ala (3a), D-Ala (3b), Gly (3c), L-Ala-L-Ala (3e), L-Leu (3f). 6'-N netilmicin derivatives: L-Ala (9a), D-Ala (9b), Gly (9c), L-Asp (9d), L-Ala-L-Ala (9e)]. Characterization was made by FAB-MS, IR, 1H-NMR, and 13C-NMR. All derivatives were essentially inactive. The nephrotoxic potential of the derivatives obtained in sufficient quantities (3b,e and 9a-e) was assessed by measuring their inhibitory potential toward the activity of lysosomal phospholipase A1 acting on phosphatidylcholine embedded in negatively-charged membranes. One compound, 6'-N-L-Ala-netilmicin (9a), showed a 2-fold decrease of inhibitory potency compared to its parent drug. A conformational analysis revealed that it adopts two equally probable conformations and orientations when interacting with phosphatidylinositol. The first in which the drug lies parallel to the hydrophobic-hydrophilic interface, is similar to that of netilmicin. The second, in which the drug inserts itself in the bilayer across the hydrophilic/hydrophobic interface, is similar to that described for streptomycin, an almost non-nephrotoxic aminoglycoside. [less ▲]

Synthesis and application of new N-heterocyclic carbene ruthenium complexes in catalysis: A case study

in Current Organic Chemistry (2006), 10(2), 203-215

New imidazolium and imidazolinium salts were synthesized and their ability to act as stable N-heterocyclic carbene (NHC) ligand precursors was investigated in various ruthenium-catalyzed processes. Thus ... [more ▼]

New imidazolium and imidazolinium salts were synthesized and their ability to act as stable N-heterocyclic carbene (NHC) ligand precursors was investigated in various ruthenium-catalyzed processes. Thus, 1,3-diarylimidazol(in)ium chlorides bearing the phenyl, 1-naphthyl, 4-biphenyl, 3,5-dimethylphenyl, 2-tolyl, 2,6-dimethylphenyl, 2,4,6-trimethylphenyl (mesityl), and 2,6-diisopropylphenyl substituents were prepared. They were combined with the [RuCl2(p-cymene)](2) dimer and potassium tert-butoxide or sodium hydride to generate the corresponding ruthenium-arene complexes [RuCl2(p-cymene)(NHC)] in situ. The catalytic activity of all these species was investigated in the photoinduced ring-opening metathesis polymerization (ROMP) of norbornene and cyclooctene. Results from this study showed that the C4-C5 double bond in the imidazole ring of the NHC ligands was not crucial to achieve high catalytic efficiencies. The presence or the absence of alkyl groups on the ortho positions of the phenyl rings had a more pronounced influence. Blocking all the ortho positions was a requisite for obtaining efficient catalysts. Failure to do so probably resulted in the ortho-metallation of the carbene ligand, thereby altering the coordination sphere of the ruthenium active centers. Catalytic screenings were also carried out with the various imidazol(in)ium salts to evaluate their ability at promoting the cyclopropanation of styrene and cyclooctene with ethyl diazoacetate. Under the experimental conditions adopted, the exact nature of the N,N'-diaryl groups had very little influence on the outcome of these reactions. The imidazolium salts were further probed as catalyst modifiers for the Atom Transfer Radical Addition (ATRA) of carbon tetrachloride to styrene. Some species displayed a dual activity and promoted both olefin metathesis and ATRA. [less ▲]

Synthesis and biodistribution of [5-131I]iodotropapride: a potential D2 dopamine receptor imaging agent.

in Nuclear Medicine & Biology (1994), 21(2), 255-62

[5-131I]Iodotropapride is a benzamidic compound which displays high affinity and selectivity for dopaminergic receptors. It was prepared from the corresponding brominated compound by a nucleophilic ... [more ▼]

[5-131I]Iodotropapride is a benzamidic compound which displays high affinity and selectivity for dopaminergic receptors. It was prepared from the corresponding brominated compound by a nucleophilic substitution with [131I]iodine (t1/2 = 8.02 days, E gamma = 364 keV) based on the use of Cu(I) as catalyst and high specific activity of [131I]NaI. After i.v. injection in rats the tracer crosses the blood-brain barrier (0.42 +/- 0.06% of injected dose in the total brain) and demonstrates a high affinity binding to the striatum. The striatum-to-cerebellum ratio increases with time and reaches values of 9 and 22 at 30 and 120 min after injection, respectively. This specific uptake in the striatum is saturable and can be blocked by pretreatment with different D2 antagonists. When labeled with 123I (t1/2 = 13 h, E1 = 159 keV), the corresponding [123I]iodotropapride may be useful for the investigation of the D2 dopamine receptors in humans with single photon emission computer tomography (SPECT). [less ▲]

Synthesis and biological effects of new 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides on insulin-secreting cells

in Pharmacy and Pharmacology Communications (2000), 6

Synthesis and biological evaluation of 5-aminothiazole and 4-amino- 1,2,4-triazole derivatives, potential inhibitors of bacterial serine enzymes

in Journal de Pharmacie de Belgique (1990, February), 45

Synthesis and biological evaluation of N-methyl-laudanosine iodide analogues as potential SK channel blockers.

in Bioorganic & Medicinal Chemistry (2005), 13(4), 1201-9

Neuronal action potentials are followed by an afterhyperpolarisation (AHP), which is mediated by small conductance Ca2+-activated K+ channels (SK channels or KCa2 channels). This AHP plays an important ... [more ▼]

Neuronal action potentials are followed by an afterhyperpolarisation (AHP), which is mediated by small conductance Ca2+-activated K+ channels (SK channels or KCa2 channels). This AHP plays an important role in regulating neuronal activity and agents modulating AHP amplitude could have a potential therapeutic interest. It was previously shown that N-methyl-bicuculline iodide blocks SK channels but its GABA) activity represents a serious drawback. In view of the structural analogy between bicuculline and laudanosine 14, several N-quaternary analogues of the latter were developed. It was shown that N-methyl-laudanosine 15 (NML) and N-ethyl-laudanosine 16 induce a reversible and relatively specific blockade of the apamin sensitive AHP in dopaminergic neurones with mean IC50s of 15, and 47 microM, respectively. Laudanosine 14, N-butyl-17 and N-benzyl-18 derivatives were less potent. In order to find pharmacophore elements, modifications were performed at different positions such as C-1, C-6 and C-7. Intracellular recordings on rat midbrain dopaminergic neurones were made in order to evaluate the putative blockade of SK channels by these molecules. Simplified structures such as tetrahydroisoquinoline derivatives with H or Me at C-1 1-6 presented no significant activity at 300 microM. The presence of a 1-(3,4-dimethoxybenzyl) moiety seems an important feature. Indeed, compound 8 showed a blockade of the AHP of only 33% at 300 microM while compound 13 blocked it by 67%, respectively, at the same concentration. Binding experiments were also performed. Binding affinities for SK channels are in good agreement with electrophysiological data. These results indicate that the presence of a charged nitrogen group is an essential point for the affinity on SK channels. Finally, because of the similar activity of both enantiomers of NML 19 and 20, the interaction site may present a symmetrical configuration. [less ▲]

Synthesis and biological evaluation of novel 2,3-dihydro-4H-1,2,4-benzothiadiazine 1,1-dioxides acting as AMPA potentiators

Poster (2004, August)

Synthesis and biological evaluation of sulfonylcyanoguanidines and sulfonamidonitroethylenes as bioisosteres of hypoglycemic sulfonylureas

in European Journal of Medicinal Chemistry (1997), 32