PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Lithium Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed2001

Comparison of patient dose from imaging protocols for dental implant planning using conventional radiography and computed tomography.

OBJECTIVES: To compare the radiation doses from imaging protocols for dental implant planning either using conventional radiography only (dental panoramic radiography (DPR), cephalometry and linear cross-sectional tomography) or involving computed tomography (CT). METHODS: Organ absorbed doses were measured using a female Rando anthropomorphic phantom loaded with lithium fluoride thermoluminescent dosemeters (TLD). Standard mandibular protocols for dental implant planning were followed using either a conventional dental radiographic unit (PM 2002 CC Planmeca, Helsinki, Finland) or CT scanner (Excel Twin Elscint, Haifa, Israel). Organ absorbed and effective doses were calculated. Effective dose was calculated using two approaches, one based on the ICRP method which excludes the salivary tissue from the remainder organs (designated E(exc)), and the other with its inclusion (E(inc)). RESULTS: The greatest individual organ doses for any examination were measured in the salivary tissue. E(exc) for panoramic, cephalometric and cross-sectional tomography using DPR was 0.004 mSv, 0.002 mSv and 0.002 mSv, respectively, whereas with CT it was 0.314 mSv. The value of E(inc) calculated using these data was between two and five times E(exc). CONCLUSIONS: E(inc) greatly increases the apparent radiation burden, especially with high dose procedures. CT techniques can provide excellent images, but at the cost of increased radiation detriment. DPR with a cross-sectional tomography facility may give adequate clinical information at a greatly reduced dose.

Absorption↗
PubMed2004

Asymmetric synthesis and applications of beta-amino Weinreb amides: asymmetric synthesis of (S)-coniine.

Conjugate addition of lithium (S)-N-benzyl-N-alpha-methylbenzylamide to a range of alpha, beta-unsaturated Weinreb amides proceeds with high levels of diastereoselectivity (>95% de). The beta-amino Weinreb amide products may be transformed into beta-amino ketones via reactions with Grignard reagents, while treatment with DIBAL-H furnishes beta-amino aldehydes. Trapping of the aldehyde via Wadsworth-Emmons reaction and subsequent manipulation offers an efficient route to homochiral delta-amino acid derivatives and 2-substituted piperidines. The application of this methodology for the synthesis of (S)-coniine is demonstrated.

Aldehydes↗
PubMed2004

Kinetic resolution of tert-butyl (RS)-3-alkylcyclopentene-1-carboxylates for the synthesis of homochiral 3-alkyl-cispentacin and 3-alkyl-transpentacin derivatives.

High levels of stereocontrol are observed in the conjugate addition of lithium dibenzylamide to tert-butyl (RS)-3-alkylcyclopentene-1-carboxylates (alkyl = Et, Bn), with addition occurring exclusively anti- to the 3-alkyl substituent. Treatment of a range of tert-butyl (RS)-3-alkylcyclopentene-1-carboxylates (alkyl = Et, Bn, (i)Pr, (t)Bu) with lithium (RS)-N-benzyl-N-[small alpha]-methylbenzylamide indicates that good enantiorecognition is observed (E > 80) in their mutual kinetic resolution. In these reactions, conjugate addition of the lithium amide occurs exclusively anti- to the 3-alkyl substituent, with subsequent C(1)-protonation occurring preferably anti- to the 2-amino group in the 3-Et, 3-Bn and 3-(i)Pr cases, giving predominantly the corresponding 1,2-syn-2,3-anti-diastereoisomers. Conjugate addition to (RS)-3-tert-butyl cyclopentene-1-carboxylate results in exclusive 2,3-anti -addition and a reversal in C(1)-protonation selectivity, giving predominantly the 1,2-anti-2,3-anti-diastereoisomer. Furthermore, the kinetic resolution of the tert-butyl (RS)-3-alkylcyclopentene-1-carboxylates (alkyl = Et, Bn, (i)Pr, (t)Bu) with lithium (S)-N-benzyl-N-alpha-methylbenzylamide proceeds efficiently, giving, at between 47 and 51% conversion, the resolved 3-alkylcyclopentene-1-carboxylates in >85 to >98% ee and the beta-amino ester products of conjugate addition in high de, consistent with E > 80 in each case. Subsequent deprotection of the 1,2-syn-2,3-anti-3-alkyl-beta-amino esters (alkyl = Et, Bn, (i)Pr) by hydrogenolysis and ester hydrolysis gives the corresponding 1,2-syn-2,3-anti-3-alkylcispentacins in >98% de and 98 +/- 1% ee. Selective epimerisation of the 1,2-syn-2,3-anti-3-alkyl-beta-amino esters (alkyl = Et, Bn, (i)Pr, (t)Bu) by treatment with KO(t)Bu in (t)BuOH gives the corresponding 1,2-anti-2,3-anti-3-alkyl-beta-amino esters in quantitative yield and in >98% de, with subsequent deprotection by hydrogenolysis and ester hydrolysis giving the corresponding 1,2-anti-2,3-anti-3-alkylcispentacin hydrochlorides in >98% de.

Amides↗
PubMed2004

Parallel kinetic resolution of tert-butyl (RS)-3-alkyl-cyclopentene-1-carboxylates for the asymmetric synthesis of 3-alkyl-cispentacin derivatives.

The double mutual kinetic resolution of tert-butyl (RS)-3-benzyl-cyclopentene-1-carboxylate with a 50 : 50 mixture of lithium (RS)-N-benzyl-N-alpha-methylbenzylamide and lithium (RS)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide gives, after protonation with 2,6-di-tert-butylphenol, a 50 : 50 mixture of the readily separable N-benzyl-(1SR,2RS,3RS,alphaRS)- and N-3,4-dimethoxybenzyl-(1SR,2RS,3RS,alphaRS)-beta-amino esters in >98% de in each case. This product distribution indicates that these amides react at very similar rates and with no mutual interference to furnish readily separable products, and are thus ideal for parallel kinetic resolution. The efficient parallel kinetic resolution (E > 65) of a range of tert-butyl (RS)-3-alkyl-cyclopentene-1-carboxylates with a pseudoenantiomeric mixture of homochiral lithium (S)-N-benzyl-N-alpha-methylbenzylamide and lithium (R)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide gives, after separation and N-deprotection, a range of carboxylate protected 3-alkyl-cispentacin derivatives in >98% de and >95% ee.

Amides↗
PubMed2005

Experimental study and Monte-Carlo simulation of the nucleation and growth processes during the dehydration of Li2SO4.H2O single crystals.

A kinetic model for the dehydration of lithium sulfate monohydrate is proposed in order to account for experimental data obtained on single crystals by thermogravimetry at 80 degrees C under fixed water vapour pressure, and by optical microscopy. This model is based on the assumptions of Mampel's model, the nucleation takes place randomly at the surface of the solid and is followed by isotropic growth toward the centre of the crystal. Calculated rates dalpha/dt are obtained by means of Monte-Carlo simulations and compared to the experimental ones, which leads to the determination of two kinetic constants: the areic frequency of nucleation (in number of nuclei m(-2) s(-1)) and the areic reactivity of growth (in mol m(-2) s(-1)).

Computer Simulation↗
PubMed2005

Unusual reactions of [{micro-(phthalazine-N2:N3)}Fe2(micro-CO)(CO)6] with organolithium reagents. A novel coordination mode of 1,2-diazane diiron carbonyl compounds.

[{Micro-(phthalazine-N2:N3)}Fe2(micro-CO)(CO)6](1) reacts with organolithium reagents, RLi (R = CH3, C6H5, p-CH3C6H4, p-CH3OC6H4, p-CF3C6H4, p-C6H5C6H4), followed by treatment with Me3SiCl to give the novel diiron carbonyl complexes with a saturated N-N six-membered diazane ring ligand, [{C6H4CH(R)NNCH2}Fe2(C=O)(CO)6](2, R = CH3; 3, R = C6H5; 4, R =p-CH3C6H4; 5, R =p-CH3OC6H4; 6, R =p-CF3C6H4; 7, R =p-C6H5C6H4). Compounds 4 and 5 were treated with [(NH4)2Ce(NO3)6] to afford the aryl-substituted phthalazine-coordinated diiron carbonyl compounds [(micro-{1-(p-CH3C6H4)-phthalazine-N2:N3})Fe2(micro-CO)(CO)6](8) and [(micro-{1-(p-CH3OC6H4)-phthalazine-N2:N3})Fe2(micro-CO)(CO)6](9), respectively. The structures of complexes 4 and 9 have been established by X-ray diffraction studies.

Diazonium Compounds↗
PubMed2006

Ligand-mediated enantioselective addition of lithium carbazolates to aldehydes.

The enantioselective synthesis of acyclic pyrrole, indole and other N-carbazole carbinols via ligand-mediated addition of lithium carbazolates to aldehydes, together with studies into their catalytic enantioselective synthesis using substoichiometric base and ligand, are reported. The subsequent exploitation of the resulting stereocentre as a controlling element in 1,3-syn- and anti-selective reduction of beta-ketones and elaboration to homoallylic alcohols is also described.

Alcohols↗
PubMed2006

Infrared spectroscopy of the Li+(H2O)Ar complex: the role of internal energy and its dependence on ion preparation.

The internal energy or effective temperature of cluster ions has become an important issue in characterizing the structures observed in these species. This report considers the role played by the method of ion preparation (laser vaporization-supersonic expansion versus ion impact-evaporative cooling) in governing the internal energy of a specific species, Li(+)(H(2)O)Ar. Vibrational predissociation spectroscopy of the O-H stretch modes revealed rotational features, which were used to characterize the structure and effective rotational temperature of the cluster ion. In addition, the impact of the lithium ion on the H(2)O molecule was analyzed in terms of the vibrational frequency shifts, relative IR intensities, and H(2)O geometry.

Argon↗
PubMed2006

Extension of molecular electronic structure methods to the solid state: computation of the cohesive energy of lithium hydride.

We describe a simple strategy for calculating the cohesive energy of certain kinds of crystal using readily available quantum chemistry techniques. The strategy involves the calculation of the electron correlation energies of a hierarchy of free clusters, and the cohesive energy E(coh) is extracted from the constant of proportionality between these correlation energies and the number of atoms in the limit of large clusters. We apply the strategy to the LiH crystal, using the MP2 and CCSD(T) schemes for the correlation energy, and show that for this material E(coh) can be obtained to an accuracy of approximately 30 meV per ion pair. Comparison with the experimental value, after correction for zero-point energy, confirms this accuracy.

Algorithms↗
PubMed1998

Effect of lithium gamma-linolenate on the growth of experimental human pancreatic carcinoma.

BACKGROUND: The lithium salt of gamma-linolenic acid (Li-GLA) is growth inhibitory to pancreatic cancer cells in vitro and is reported to prolong the survival of patients with pancreatic cancer. The effect of Li-GLA on the growth of human pancreatic carcinoma in vivo is not known. In this study the effect of parenterally administered Li-GLA on the growth of human pancreatic carcinoma in nude mice was tested. METHODS: Pancreatic tumours were produced in nude mice by subcutaneous implantation of MIA PaCa-2 cells. This cell line is sensitive to Li-GLA in vitro. Mice were randomly treated with intraperitoneal, intravenous or intratumoral Li-GLA. Each group also had controls. RESULTS: Both intravenous and intraperitoneal administration of Li-GLA had no significant effect on tumour growth or tumour phospholipid fatty acid composition. Intratumoral administration of Li-GLA was, however, associated with a significant antitumour effect. CONCLUSION: Within the limitations of this tumour model, the benefit seen with intravenous Li-GLA in patients with pancreatic carcinoma cannot be explained by tumour growth inhibition. Local administration appears to be more effective than intravenous or intraperitoneal therapy.

Animals↗
PubMed1999

Pathology and outcome of surgical treatment for lithium-associated hyperparathyroidism.

BACKGROUND: Hyperparathyroidism associated with long-term lithium therapy is well described. However, few studies have clearly defined the pathological findings or looked at the outcome of surgical treatment. METHODS: The study was a retrospective review of 11 patients with bipolar affective disorder who had surgery for lithium-associated hyperparathyroidism. RESULTS: Twelve patients were identified who had received lithium therapy, of whom 11 (nine women and two men, aged 46-84 (mean 65) years) had prolonged treatment from 2 to 30 (mean 15.3) years. At operation a single adenoma was identified in six patients, whereas multigland disease was seen in five patients. All patients resumed lithium treatment after operation. One patient had recurrent hyperparathyroidism at 3 years, while another had an increased serum level of parathyroid hormone in the presence of a normal serum calcium level after 1 year. CONCLUSION: Hyperparathyroidism associated with lithium may be due to either parathyroid hyperplasia or adenoma. Observations in the present study supported a true cause and effect relationship. Routine bilateral neck exploration should be performed because of a relatively high frequency of multigland involvement. However, parathyroid resection should be limited to evident disease.

Aged↗