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PubMed2005

Zirconium complexes having a chiral phosphanylamide in the co-ordination sphere.

The chiral phosphanylamido ligand, (N(CHMePh)(PPh2))-, has been introduced into co-ordination chemistry. As starting material the oily amines HN(R-*CHMePh)(PPh2)(1a) and HN(S-*CHMePh)(PPh2)(1b) were used. To reconfirm their absolute structure, 1b was oxidized with H2O2 in air to obtain HN(S-*CHMePh)(P(O)Ph2)(2) as a solid compound. The solid-state structure of 2 was established by single-crystal X-ray diffraction. The lithium salts of both enantiomers Li(N(R-*CHMePh)(PPh2))(3a) and Li(N(S-*CHMePh)(PPh2))(3b) were prepared by deprotonation reaction of 1a,b. Compounds 3a,b were further reacted with zirconocen dichloride to give the chiral metallocenes [(eta5-C5H5)2Zr(Cl)(eta2-N(R-*CHMePh)(PPh2))](4a) and [(eta5-C5H5)2Zr(Cl)(eta2-N(S-*CHMePh)(PPh2))](4b). In an alternative approach to give chiral zirconium compounds, the neutral amine 1b was reacted with [(PhCH2)4Zr] to give the enantiomeric pure complex [(PhCH2)3Zr(eta2-N(S-*CHMePh)(PPh2))](5). The solid-state structures of all zirconium complexes were determined by single-crystal X-ray diffraction.

Journal Article↗
PubMed1996

Preparation and Characterization of Halogen-Boron-Phosphorus Compounds. X-ray Crystal Structures of X(3)B.P(SiMe(3))(3) and [X(2)BP(SiMe(3))(2)](2) (X = Cl, Br).

The 1:1 mole ratio reactions of boron trihalides (BX(3)) with tris(trimethylsilyl)phosphine [P(SiMe(3))(3)] produced 1:1 Lewis acid/base adducts [X(3)B.P(SiMe(3))(3), X = Cl (1), Br (2), I (5)]. Analogous 1:1 mole ratio reactions of these boron trihalides with lithium bis(trimethylsilyl)phosphide [LiP(SiMe(3))(2)] produced dimeric boron-phosphorus ring compounds {[X(2)BP(SiMe(3))(2)](2), X = Br (3), Cl (4)}. X-ray crystallographic studies were successfully conducted on compounds 1-4. Compound 1 crystallized in the orthorhombic space group Pbca, with a = 13.420(3) Å, b = 17.044(5) Å, c = 21.731(7) Å, V = 4970.6(25) Å(3), and D(calc) = 1.229 g cm(-3) for Z = 8; the B-P bond length was 2.022(9) Å, Compound 2 crystallized in the orthorhombic space group Pbca, with a = 13.581(6) Å, b = 17.106(7) Å, c = 22.021(9) Å, V = 5116(4) Å(3), and D(calc) = 1.540 g cm(-3) for Z = 8; the B-P bond length was 2.00(2) Å. Compound 3 crystallized in the monoclinic space group P2(1)/n, with a = 9.063(5) Å, b = 16.391(8) Å, c = 9.331(4) Å, V = 1379.2(12) Å(3), and D(calc) = 1.676 g cm(-3) for Z = 2; the B-P bond length was 2.023(10) Å. Compound 4 crystallized in the monoclinic space group P2(1)/n, with a = 9.143(5) Å, b = 16.021(8) Å, c = 9.170(4) Å, V = 1342.2(11) Å(3), and D(calc) = 1.282 g cm(-3) for Z = 2; the B-P bond length was 2.025(3) Å. Thermal decomposition studies were performed on compounds 1-4, yielding colored powders with boron:phosphorus ratios greater than 1:1 and significant C and H contamination indicated by elemental analyses.

Journal Article↗
PubMed1999

Synthesis and Structural Characterization of (1,4-Dihydropyrid-1-yl)aluminum Complexes.

The reaction between LiAlH(4) and pyridine, 4-methylpyridine, or 3,5-dimethylpyridine results in hydride transfer to the pyridine ring to give tetrakis(pyridine)lithium tetrakis(1,4-dihydropyrid-1-yl)aluminate(III), 1, tetrakis(4-methylpyridine)lithium tetrakis(1,4-dihydro-4-methylpyrid-1-yl)aluminate(III), 2, or tetrakis(3,5-dimethylpyridine)lithium tetrakis(3,5-dimethyl-1,4-dihydropyrid-1-yl)aluminate(III), 3, respectively. We claim that 1, instead of lithium tetrakis(1,4-dihydropyrid-1-yl)aluminate(III), is the compound which is known as Lansbury's reagent. Treatment of trimethylamine-alane, AlH(3).NMe(3), with pyridine yields tris(1,4-dihydropyrid-1-yl)(pyridine)aluminum, 4. It could be shown that AlH(3).NMe(3) initially reduces pyridine to 1,2-dihydropyridine, which is subsequently converted into its 1,4-isomer. The X-ray crystal structures of 1-4 were determined. While the differences between Al-N distances within each of the compounds 1-3 are not significant, 4 exhibits two distinctly different types of Al-N bonds, the dative bond between Al and N(pyridine), d(Al-N) = 1.959(2) Å, and the covalent bonds between Al and N(1,4-dihydropyrid-1-yl), d(av)(Al-N) = 1.833 Å.

Journal Article↗
PubMed1999

[3H]Azidodantrolene: synthesis and use in identification of a putative skeletal muscle dantrolene binding site in sarcoplasmic reticulum.

Dantrolene sodium is a medically important hydantoin derivative that interferes with release of Ca2+ from intracellular stores of skeletal muscle by an unknown mechanism. Identification of the molecular target of dantrolene would greatly aid in understanding both the mechanism of action of the drug and the dynamics of intracellular Ca2+ release in muscle. [3H]Azidodantrolene was designed and synthesized as a photoaffinity analogue in order to identify a putative dantrolene receptor in skeletal muscle. Introduction of 1 mole-atom of tritium into aldehyde 5b was required during radioligand synthesis in order to ensure high enough specific activity for detection of photo-cross-linked proteins by fluorographic methods. This was accomplished by reduction of ester 3 with custom synthesized, 100% tritium-labeled lithium triethylborotritide, followed by oxidation to 5b by manganese(IV) oxide. Compound 6b was demonstrated to be >/=95% tritium-labeled at the imine position by NMR spectroscopy, and the specific radioactivity of [3H]azidodantrolene sodium was empirically determined by HPLC and liquid scintillation counting to be 24.4 Ci/mmol, approximately 85% of theoretical maximum. [3H]Azidodantrolene was found to be pharmacologically active in ligand-receptor binding studies with skeletal muscle sarcoplasmic reticulum membranes. Photo-cross-linking experiments analyzed by SDS-PAGE and tritium fluorography have identified a approximately 160-kDa specifically labeled protein as the putative, intracellular, skeletal muscle dantrolene receptor. This photolabeled protein comigrates with a protein in Western blots immunologically cross-reactive to a polyclonal anti-rabbit skeletal muscle ryanodine receptor antibody. Thus, the putative dantrolene receptor may be related to the skeletal muscle ryanodine receptor.

Animals↗
PubMed1999

Synthesis of Succinimido[3,4-b]indane and 1,2,3,4,5,6-Hexahydro-1,5-methano-3-benzazocine-2,4-dione by Sequential Alkylation and Intramolecular Arylation of Enolates Derived from N,N,N'N'-Tetramethylbutanediamides and N,N,N'N'-Tetramethylpentanediamides.

The tricyclic title compounds, 4 and 5, were synthesized by initial alkylation of the lithium monoenolates of N,N,N',N'-tetramethylbutanediamide (6) and N,N,N',N'-tetramethylpentanediamide (19) with 2-iodobenzyl chloride in liquid NH(3) at -60 degrees C to afford 2-(2-iodobenzyl)-N,N,N',N'-tetramethylbutanediamide (9) and 2-(2-iodobenzyl)-N,N,N',N'-tetramethylpentanediamide (20) in yields of 88 and 87%, respectively. Treatment of 9 with KNH(2) in liquid NH(3) resulted in formation and intramolecular arylation of the less-substituted alpha-enolate to produce trans-1,2-bis(N,N-dimethylcarboxamido)indane (10a) in 60% yield. Selective hydrolysis of 10a with aqueous Na(2)O(2) gave trans-1-(N,N-dimethylcarboxamido)indane-2-carboxylic acid (17), which was then converted to bridged succinimide 4 by transformation to trans-1-(N,N-dimethylcarboxamido)indane-2-carboxamide (10c) followed by cyclization of this mixed primary/tertiary amide by means of NaH in refluxing THF. Treatment of 20 with KNH(2) in liquid NH(3) led to intramolecular arylation and accompanying ammonolysis to afford trans-1-(N,N-dimethylcarboxamido)-1,2,3,4-tetrahydronaphthalene-3-carboxamide (21b). Conversion of 21b to 5 was similarly effected by means of NaH. Experiments designed to test the mechanistic aspects of the intramolecular arylations provided evidence for competing aryne and SET pathways.

Journal Article↗
PubMed2006

Syntheses and characterization of lithium alkyl mono- and dicarbonates as components of surface films in Li-ion batteries.

A homologous series of lithium alkyl mono- and dicarbonate salts was synthesized as model reference compounds for the frequently proposed components constituting the electrolyte/electrode interface in Li-ion batteries. The physicochemical characterization of these reference compounds in the bulk state using thermal analyses and X-ray photoelectron, nuclear magnetic resonance, and Fourier transform infrared spectroscopies establishes a reliable database of comparison for the studies on the surface chemistry of electrodes harvested from Li-ion cells.

Journal Article↗
PubMed1996

The effect of the potassium channel activator, cromakalim, on antidepressant drugs in the forced swimming test in mice.

The forced swimming test (FST) is a widely used behavioural model to predict potential antidepressant (AD) action of compounds in humans. It has been previously shown that pretreatment with lithium, quinine and clonidine had additive effects on AD drugs in the FST, an effect proposed to be a result of potassium channel blockade. It is possible that pretreatment with potassium channel openers may induce opposite effects to those seen following pretreatment with potassium channel blockers in the FST. Pretreatment with cromakalim (CROM) (1 mg/kg, intraperitoneally [i.p.]) antagonized the anti-immobility effect of the mixed noradrenaline (NA)/5-hydroxytryptamine (5-HT) reuptake inhibitors imipramine and amitriptyline (P < 0.05). CROM administration (0.06 and 1 mg/kg, i.p.) also blocked the AD-like effects of the specific NA reuptake inhibitor, desipramine, and the selective serotonin reuptake inhibitor, paroxetine (P < 0.05 and P < 0.01, respectively). Pretreatment with CROM via gavage (1 mg/kg) antagonized the AD-like effects of imipramine, amitiptyline, desipramine and paroxetine. CROM treatment (via i.p. route or gavage) did not have any significant effect on the anti-immobility activity of the atypical AD mianserin at any of the doses employed. Another potassium channel opener, minoxidil (MINOX), which does not cross the blood-brain barrier, was also tested to eliminate the possibility that CROM may be acting via peripheral/local mechanisms. MINOX (32 mg/kg) failed to antagonize anti-immobility effects of any of the AD tested. In conclusion, the results of the present study suggest that CROM is only acting on drugs involved with neurotransmitter uptake inhibition.

Amitriptyline↗
PubMed1994

High-yield production of oxalic acid for metal leaching processes by Aspergillus niger.

The complex-forming compound oxalic acid can effectively solubilise metals such as aluminium, iron, lithium and manganese. In order to produce high amounts of oxalic acid for biohydrometallurgical processes, it was the aim of this work to optimise oxalic acid production by Aspergillus niger, a fungus well known for its ability to produce oxalic acid. A. niger excreted 427 mmol oxalic acid l-1 if it was cultivated in a pH-controlled (pH 6.0) fed-batch run in a 2-l stirred tank reactor. Sucrose and lactose permeate were suitable carbon sources for oxalic acid production. In sucrose medium, A. niger produced high amounts of gluconic and oxalic acids, whereas in lactose permeate medium only oxalic acid was produced. Cultivation in green syrup and molasses media lead to high yields of biomass, but low oxalic acid production (< 20 mmol l-1).

Aspergillus niger↗
PubMed1968

Active sugar transport by the small intestine. The effects of sugars, amino acids, hexosamines, sulfhydryl-reacting compounds, and cations on the preferential binding of D-glucose to tris-disrupted brush borders.

Tris-disrupted and intact brush border membrane preparations from mucosa of hamster jejunum were capable of preferentially binding actively transported D-glucose in a similar manner. Density gradient centrifugation of the Tris-disrupted brush borders indicated that D-glucose was bound to a fraction containing the cores or inner material of the microvilli. The properties of this binding were examined with the Tris-disrupted brush border preparation. Actively transported sugars competitively inhibited preferential D-glucose binding, whereas no effect was observed with nonactively transported sugars. Neither actively nor nonactively transported amino acids affected D-glucose binding. D-Glucosamine, which is not actively transported, was inhibitory to preferential D-glucose binding as well as to the active transport of D-glucose by everted sacs of hamster jejunum. No inhibitory effect was observed with the same concentration of D-galactosamine. Preferential D-glucose binding was also inhibited by sulfhydryl-reacting compounds, Ca(2+), and Li(+) ions. On the other hand, Mg(2+) was shown to be stimulatory and Na(+), NH(4) (+), and K(+) had no effect on this phenomenon. The results of these experiments suggest that preferential D-glucose binding to brush borders is related to the initial step in active sugar transport by the small intestine.

Amino Acids↗
PubMed2005

Synthesis and structure of diamido ether uranium(IV) and thorium(IV) halide "ate" complexes and their conversion to salt-free bis(alkyl) complexes.

The high-yield synthesis, spectroscopic and structural determination of three new uranium(IV) and thorium(IV)ate complexes supported by three different diamido ether ligands are reported. The reaction of Li2[2,6-iPr2PhN(CH2CH2)]2O (Li2[DIPPNCOCN]) with 1 equiv. of UCl4 in THF generates [DIPPNCOCN]UCl3Li(THF)2(1), while reaction in toluene/ether gives salt-free [DIPPNCOCN]UCl2.1/2C7H8(2), which was identified by paramagnetically shifted 1H NMR. Reaction of 0.5 equiv. of {[tBuNON]UCl2}2([tBuNON]=[(CH3)3CN(Si(CH3)2)]2O2-) with 3.5 equiv. LiI in toluene and a minimal amount of THF results in [tBuNON]UI3Li(THF)2(3) and is very similar in structure to 1. {[MesNON]ThCl3Li(THF)}2(4), a dimeric complex with a Th2Li2Cl6 core, is prepared by reaction of Li2[2,4,6-Me3PhN(Si(CH3)2)]2O (Li2[MesNON]) with ThCl4 in THF. The analogous reaction in toluene did not yield the salt-free complex but rather a sterically crowded diligated compound, [MesNON]2Th (5), which was also structurally characterized. Complex 5 was prepared rationally by reacting 2 equiv. Li2[MesNON] with ThCl4 in toluene. The reaction of 1 and 3 with 2 equiv. of LiCH2Si(CH3)3 generates the stable, salt-free organoactinides [DIPPNCOCN]U(CH2Si(CH3)3)2(6) and [tBuNON]U(CH2Si(CH3)3)2(7). Complex 6 was structurally characterized. These reactions illustrate the viability of ate complexes as useful synthetic precursors.

Chlorides↗
PubMed2005

Cyclization of lithiated pyridine and quinoline carboxamides: synthesis of partially saturated pyrrolopyridines and spirocyclic beta-lactams.

Lithiation of N-benzyl pyridine and quinoline carboxamides alpha to nitrogen gives anions that undergo intramolecular attack on the pyridine or quinoline ring, either directly or on activation of the ring by N-acylation. The resulting four-, five-, or six-membered-ring-containing compound may be oxidized, protonated, alkylated, or acylated to give a range of polycyclic heterocycles, including pyrrolopyridines, pyrroloquinolines, benzonaphthyridines, and azaspirocyclic beta-lactams. [reaction: see text]

Cyclization↗
PubMed1997

Efficient and beta-stereoselective synthesis of 4(5)-methyl-5(4)-(5-amino-5-deoxy-beta-D-ribofuranosyl)imidazole and related compounds exhibiting antiulcer activity.

The reaction of 2,3,5-tri-O-benzyl-D-ribose with the lithium salt of an imidazole derivative gave an adduct 17RS. Treatment of 17RS with 1.5N HCl in refluxing tetrahydrofuran gave the beta-4(5)-ribofuranosylimidazole 19 (35%) and the ribosylimidazole 18 (51%). The latter was converted into beta-19 in 86% yield by the Mitsunobu cyclization. This synthetic method produced only the desired beta-anomer. Protection of the imidazole nitrogen of 19 with an ethoxycarbonyl group followed by debenzylation gave 21, which was successively derived to the 5'-amino derivative 1 via the 5'-substituted phthalimide 23, followed by hydrazine degradation in excellent yield. Compound 1 was then converted into the 5'-cyanoguanidine 2 in 79% yield. The 5'-amino derivatives 3-9 lacking a methyl group were efficiently synthesized. Among them, the cyanoguanidine 5 and phenylthiourea 8 exhibited antiulcer activities with half the efficacy of cimetidine. The molecular conformation of 5 was determined by X-ray structure analysis.

Animals↗
PubMed2006

Structure and reaction pathway of TMP-Zincate: amido base or alkyl base?

The novel directed ortho metalation (DoM) reagents for functionalized aromatic rings, TMP-Zn-ates (R2Zn(TMP)Li (R = Me, 1; tBu, 2)), have been reported to be synthetically useful for the chemo- and regioselective construction of multi-functionalized aromatic compounds. Here, we present the first comprehensive structural and mechanistic investigation by means of X-ray, NMR, and DFT studies on the DoM reaction employing our original TMP-Zn-ate base. The structures of TMP-Zn-ates in solution and in the solid state were determined. The DFT study strongly suggested that the deprotonation involving the TMP ligand on the TMP-Zn-ate is kinetically more favorable than that involving the alkyl ligand, and this view was supported by monitoring of the 13C NMR spectrum of the reaction mixture.

Crystallography, X-Ray↗
PubMed2003

Amine- and ether-chelated aryllithium reagents-structure and dynamics.

Chelation and aggregation in phenyllithium reagents with potential 6- and 7-ring chelating amine (2, 3) and 5-, 6-, and 7-ring chelating ether (4, 5, 6) ortho substituents have been examined utilizing variable temperature (6)Li and (13)C NMR spectroscopy, (6)Li and (15)N isotope labeling, and the effects of solvent additives. The 5- and 6-ring ether chelates (4, 5) compete well with THF, but the 6-ring amine chelate (2) barely does, and 7-ring amine chelate (3) does not. Compared to model compounds (e.g., 2-ethylphenyllithium 7), which are largely monomeric in THF, the chelated compounds all show enhanced dimerization (as measured by K = [D]/[M](2)) by factors ranging from 40 (for 6) to more than 200 000 (for 4 and 5). Chelation isomers are seen for the dimers of 5 and 6, but a chelate structure could be assigned only for 2-(2-dimethylaminoethyl)phenyllithium (2), which has an A-type structure (both amino groups chelated to the same lithium in the dimer) based on NMR coupling in the (15)N, (6)Li labeled compound. Unlike the dimer, the monomer of 2 is not detectably chelated. With the exception of 2-(methoxymethyl)phenyllithium (4), which forms an open dimer (12) and a pentacoordinate monomer (13), the lithium reagents all form monomeric nonchelated adducts with PMDTA.

Journal Article↗
PubMed2005

Transport mechanism and substrate specificity of human organic anion transporter 2 (hOat2 [SLC22A7]).

Human organic anion transporter 2 (hOat2[SLC22A7]) is highly expressed in the human liver. Although localization, gene expression, substrate specificity and transport mechanisms of other human Oat isoforms such as human Oat1 (hOat1), human Oat3 (hOat3) and human Oat4 (hOat4) have been elucidated, information concerning human Oat2 (hOat2) is less defined. The objective of this study was to provide further information on the transport mechanism and substrate specificity of hOat2. When expressed in Xenopus laevis oocytes, the transport of organic compounds mediated by hOat2 was not affected by the replacement of extracellular sodium with lithium, choline and mannitol. The uptake of estrone sulfate (ES) in hOat2-expressing oocytes was significantly trans-stimulated by preloading the oocytes with fumarate and succinate, but not glutarate. Moreover, we observed that hOat2 mediates the transport of bumetanide, ES, glutarate, dehydroepiandrosterone sulfate, allopurinol, prostaglandin E2, 5-fluorouracil, paclitaxel and L-ascorbic acid. These compounds are identified for the first time as hOat2 substrates. A wide range of structurally unrelated organic compounds inhibited the hOat2-mediated uptake of tetracycline, except for sulfobromophthalein. All of these findings indicate that hOat2 is a sodium-independent multi-specific organic anion/dimethyldicarboxylate exchanger. Our present findings thus provide further insights into the role of hOat2 in hepatic drug transport.

Animals↗
PubMed1983

Influence of lithium on biochemical manifestations of striatal dopamine target cell supersensitivity induced by prolonged haloperidol treatment.

The effects of prolonged treatment with dietary lithium and/or haloperidol (infused by means of osmotic minipumps) on biochemical parameters indicative of striatal dopamine target cell supersensitivity have been investigated in the rat. When given concomitantly with haloperidol, lithium failed to prevent the fall of striatal dopamine metabolites observed 2 days following withdrawal and the tolerance to the elevation of dopamine metabolites in response to challenge with the neuroleptic during withdrawal. Prolonged treatment with lithium also failed to modify the changes in nigral dihydroxyphenylacetic acid levels and in striatal acetylcholine levels which occur under chronic neuroleptic treatment. Chronic dietary lithium alone consistently elevated substance P levels in substantia nigra. The usual decrease in nigral levels of the peptide that occurs in response to chronic treatment with haloperidol was prevented in animals treated concomitantly with lithium. These data suggest that the mechanism whereby lithium stabilizes dopaminergic supersensitivity does not seem to involve an action of the compound on the neuronal mechanisms regulating the activity of the nigro-striatal dopaminergic system or on striatal cholinergic neurons but may be related to the restoration of normal striato-nigral substance P ergic transmission.

3,4-Dihydroxyphenylacetic Acid↗