SEARCH · PubMed Health
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.
[reaction: see text] A formal total synthesis of racemic spatol is presented. The key steps involved a 4 + 3 cycloaddition of a halogenated cyclopentenyl cation to cyclopentadiene and a quasi-Favorskii rearrangement.
[formula: see text] Pd-catalyzed reaction of iododienes and iodoarylalkenes represented by 1, 8, and 10 under 1 atm of CO and a small amount of O2 in the presence of a base, e.g., NEt3, as well as MeOH and H2O in DMF can undergo a highly diastereoselective cyclic carbopalladation-carbonylative esterification tandem process (Type II C-Pd process) to give in high yields the corresponding ester-containing cyclization products, e.g., 2, 9, and 11, in as high as 98% diastereoselectivity.
Explore the source record for details and available documents.
The practical and convenient synthesis of hotrienol, which is an excellent fruity smelling compound, has been performed by the ene-type chlorination of linalyl acetate and then dehydrochlorinated by lithium bromide and lithium carbonate in DMF, followed by hydrolysis in three steps with an overall yield of 55%.
Explore the source record for details and available documents.
The creep of microspecimens of posterior dental composites was studied using a torsional creep apparatus. Shear stresses were maintained for 3 h and recovery was followed for 50 h. Creep curves were obtained at 21, 37, and 50 degrees C and four torque levels. The effect of conditioning the specimens in water up to 8 weeks was studied. The posterior composites exhibited linear viscoelastic behavior at low deformations. They had higher shear moduli and greater resistance to creep than conventional and microfilled composites. In aging experiments, maximum shear moduli occurred when specimens were 48 h to 1 week old. Subsequent softening was attributed to water absorption. Residual strain was highest when the composites were stressed within 24 h of initiating polymerization. Residual strain was very low in specimens 48 h to 8 weeks of age.
Planar structures of tripropeptins (TPPs) were elucidated by spectroscopic studies including various NMR measurements. Stereochemistry of constituent amino acids of tripropeptin C (TPPC) (3) was identified by marfey's method except hydroxyproline which was determined by studies of NMR and CD spectra. The absolute structure of 3 was determined by analyses of the fragments obtained by Birch reduction and LiBH4 reduction of 3. The configuration of the fatty acid, isolated from acid hydrolysate of 3, was determined to be (3R)-hydroxy-13-methyltetradecanoic acid from MS, NMR spectra and negative sign of the optical rotation.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
n-Propyl-delta-8-tetrahydrocannabinol (n-propyl-delta-8-THC and n-propyl-delta-9-THC were synthesized by condensation of (1S)-cis-verbenol with 5-n-propyl-1,3-dihydroxybenzene and administered to male Charles River CD-1 mice. Hepatic metabolites were isolated by solvent extraction and chromatography on Sephadex LH-20 and identified by gas chromatography/mass spectrometry. Seven metabolites were identified from each cannabinoid. Metabolism was similar to that previously observed from the penyl homologues, with the major biotransformation pathway being the production of 11-hydroxy-propyl-THCs and their oxidation to carboxylic acid metabolites. Other metabolites were mainly hydroxylated derivatives of these compounds and the corresponding 11-alcohol. Less hydroxylation at C(8) was found with n-propyl-delta-9-THC than with the pentyl homologue, and the monohydroxy metabolite, 8-alpha-hydroxy-n-propyl-delta-9-THC, was not observed, even though it was a prominent metabolite from delta-9-THC itself. Hydroxylation occurred in the side-chain at C(2').
STATEMENT OF PROBLEM: There is little information regarding bond strengths of resin cements to cast titanium surfaces contaminated by investment material. PURPOSE: This study examined the effect of surface contamination on the shear bond strength of resin cements to cast titanium and Ti-6Al-4V alloy. MATERIAL AND METHODS: Two types of disks were cast from commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy ingots using an argon-arc pressure casting unit and a phosphate-bonded Al2 O3 /LiAlSiO6 investment. After casting, disks were subjected to 3 surface treatments: (1) cast surface sandblasted (50 microm-sized Al2 O3 ) for 30 seconds; (2) metal surface sanded with silicon-carbide paper (600 grit) after grinding the contaminated cast surface (approximately 200 microm in thickness); and (3) metal surface sandblasted for 30 seconds after treatment 2. Surface structures were examined after each treatment with SEM and optical microscopy. Each type of disk was then bonded with 2 types of luting materials. Bonded specimens were subjected to thermocycling for up to 50,000 cycles, and shear bond strengths were determined after 0 (baseline) and 50,000 thermocycles. Results were statistically analyzed with 3-way ANOVA (P <.05). RESULTS: Microscopic observation of cast CP-Ti and Ti-6Al-4V exhibited noticeable structures on the cast surfaces apparently contaminated with investment material. However, there were no statistical differences (P >.05) in the bond strengths of both cements between contaminated (treatment 1) and uncontaminated surfaces (treatment 3) for both metals at baseline and after 50,000 thermocycles. The bond strength of specimens sanded with silicon-carbide paper (treatment 2) deteriorated dramatically after 50,000 thermocycles. CONCLUSIONS: Contamination of the cast metal surfaces by elements of the investment during casting did not affect bond strengths of the luting materials to CP-Ti and Ti-6Al-4V.
AIMS AND BACKGROUND: Since interleukin-8 (IL-8) has a suppressive effect on hematopoiesis, lithium induces leukocytosis and granulocytosis and mononuclear cells are defective in patients affected by neoplastic disease, we analyzed IL-8 production by monocytes obtained from patients with nonmetastatic breast cancer (BCaM0) and metastatic breast cancer (BCaM1) and the effect of lithium chloride (LiCl) on these cells. Lithium salt compounds are used to limit the degree and duration of neutropenia in patients receiving chemotherapy for cancer and acute leukemia. Lithium influences the hematopoietic system, which is known to be regulated by numerous cytokines including IL-8. METHODS: We selected three groups of subjects (15 per group): patients affected by BCaM0, BCaM1 and healthy donors (HD) matched for sex and age. IL-8 release was assessed in supernatants of lipopolysaccharide (LPS) and/or LiCl-treated monocyte cultures. RESULTS: Monocytes from BCaM1 released higher IL-8 levels than monocytes from BCaM0 (P <0.0001); the IL-8 levels of both groups were significantly higher (P <0.0001) than those of HD. In vitro LiCl treatment reduced IL-8 production by monocytes obtained from all subjects compared to the same cells when untreated or LPS treated. The suppressive effect of LiCl on IL-8 production by monocytes from breast cancer patients was particularly marked in monocytes from BCaM0 with respect to those from BCaM1. LPS treatment increased the IL-8 production more in BCaM1 monocytes than in BCaM0 monocytes. Moreover, combined LPS/LiCl treatment of monocytes significantly (p <0.0001) downregulated the release of IL-8 compared to treatment with LPS alone. CONCLUSIONS: Our data demonstrate that monocytes from BCaM0 release larger amounts of IL-8 than monocytes from BCaM0 and from HD. Lithium was able to downregulate IL-8 production by monocytes from different subgroups. Further studies are needed to clarify if the improvement of the hematopoietic system in vivo observed following lithium therapy could reside, at least in part, in the ability of lithium to downregulate this chemokine.
Lithium specifically and potentially inhibits membrane transport of choline. However, the effect of lithium on human neuronal choline content is unknown. This study was performed to determine if lithium alters the human brain choline concentration in vivo. In vivo proton magnetic resonance spectroscopy was used to compare the relative brain concentration of choline-containing compounds in seven lithium-treated patients and six lithium-free controls. No significant difference was observed in the mean relative choline resonance between the patient and control groups. Lithium treatment did not appear to alter the overall brain content of choline-containing compounds. It remains possible that a component of these compounds, particularly free choline, is elevated during lithium treatment.
A novel and facile synthesis of 5-hydroxy-4-hydroxymethyl-2-cyclohexenylguanine 1 is described. The key steps involve a Diels-Alder reaction of ethyl (2E)-3-acetyloxy-2-propenoate 2 as dienophile with Danishefsky's diene 3 to build up the six-membered ring skeleton, a Fraser-Reid reductive rearrangement of the adduct using LiAlH(4), and base-moiety introduction using a Mitsunobu reaction. Optically pure D- and L-1 were obtained via resolution of intermediate 7 with (R)-(-)-methylmandelic acid. The synthetic procedure toward racemic 1 consists of only five steps and has proven to be highly efficient toward the synthesis of cyclohexenyl nucleosides.
Four triene monoepoxides of arachidonic acid have been identified as endogenous components of human plasma, the epoxy groups being in the 5,6-, 8,9-, 11,12- and 14,15-positions. Prior to trimethylsilylation and gas chromatographic-mass spectrometric analysis, both the expoxy and ester functions were reduced to hydroxy groups and the double bonds were hydrogenated catalytically. Saturation of the double bonds gave diagnostic spectra that were suitable for elucidating the position of the epoxy group. The shift in the fragmentation of a deuteriated sample verified the presence of the intact epoxides prior to chemical reduction. The presence of the double bonds in the epoxy molecules was demonstrated by reduction using homogeneous catalysis with tris(triphenylphosphine)rhodium(I) chloride and deuterium.
Explore the source record for details and available documents.
High chemoselectivity can be achieved in the addition of lithium dithiane anions to vinyl epoxides exploiting the steric nature of the dithiane substituent. Unencumbered dithiane anions afford SN2 adducts, whereas sterically encumbered anions lead primarily to SN2' adducts. Furthermore, the SN2' addition occurs syn to the vinyl epoxide.
Given the putative role of inositol monophosphatase (IMPase) as the molecular target for the therapeutic effects of lithium, inhibitors of this enzyme have been proposed to be lithium-mimetics. Although cation and natural product inhibitors of IMPase have been described, these have not proved suitable for cell culture studies due to a lack of specificity. On the other hand, substrate (inositol 1-phosphate)-based inhibitors have proved useful for showing that this class of compounds mimic lithium with respect to effects on the phosphatidylinositol (PI) cell-signaling pathway. However, since these compounds are highly charged, their polarity means they are not suitable for in vivo use. Finally, the recent elucidation of the structure and mechanism of IMPase may provide the opportunity to develop compounds which specifically interact with key structural and mechanistic features of the enzyme and would represent novel structure- or mechanism-based inhibitors.