Search results for "Acetal"
showing 10 items of 154 documents
Enantioselective synthesis of 2-substituted-1,4-diketones from (S)-mandelic acid enolate and α,β-enones
2006
[EN] An approach for the synthesis of chiral non-racemic 2-substituted-1,4-diketones from (S)-mandelic acid and ¿,ß-enones has been developed. The reaction of lithium enolate of the 1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with ¿,ß-unsaturated carbonyl compounds proceeds readily to give the corresponding Michael adducts in good yields and with high diastereoselectivities. The addition of HMPA (3 equiv) reverses and strongly enhances the diastereoselectivity of the reaction. A change in the reaction mechanism from a lithium catalyzed to the one where catalysis has been suppressed by coordination of HMPA to lithium is proposed to explain these resul…
Effects of ethanol and acetaldehyde on phagocytic functions
1985
Although a number of skin diseases are characterized by the presence of an increased number of phagocytes in their lesions, the effects of alcohol on phagocytic functions are not clearly understood. Therefore, we measured the influence of ethanol and acetaldehyde on the generation of oxygen radicals, chemotaxis and the release of lysosomal enzymes from human phagocytes. We added 0.03%-3% ethanol and 0.005%-0.25% acetaldehyde to cell cultures. We found that both ethanol and acetaldehyde suppressed the generation of oxygen radicals from granulocytes and monocytes; the ID50 was achieved at concentrations of approximately 0.25% for ethanol and 0.03% for acetaldehyde. A significant inhibition of…
"Only Spinal Fixation" as Surgical Treatment of Cervical Myelopathy Related to Ossified Posterior Longitudinal Ligament: Review of 52 Cases.
2020
Background Ossification of the posterior longitudinal ligament (OPLL) is a hyperostotic condition resulting in a progressive narrowing of the spinal canal and subsequent neurologic deficits. Although systemic and local factors in combination with genetic abnormality have been considered in its etiopathogenesis, OPLL remains a poorly understood pathology. Surgical management of OPLL and the choice of the most appropriate treatment are still controversial issues. Here the authors report a series of OPLL-affected patients treated by “only-fixation” technique. Methods Between June 2012 and June 2019, 52 patients having OPLL were treated by a surgical strategy involving only spinal fixation with…
Metabolism of [3-14C]coumarin to polar and covalently bound products by hepatic microsomes from the rat, Syrian hamster, gerbil and humans.
1992
The metabolism of 0.19 and 2.0 mM-[3-14C]coumarin to polar products and covalently bound metabolites has been studied with hepatic microsomes from the rat, Syrian hamster, Mongolian gerbil and humans. [3-14C]Coumarin was metabolized by liver microsomes from all species to a number of polar products and to metabolite(s) that became covalently bound to microsomal proteins. The polar products included 3-, 5- and 7-hydroxycoumarins, o-hydroxyphenylacetaldehyde and o-hydroxyphenylacetic acid. Coumarin 7-hydroxylation was observed in all species except the rat. With 0.19 mM-[3-14C]coumarin, 7-hydroxycoumarin was the major metabolite in human liver microsomes, whereas in the other species with 0.1…
Airway Responsiveness to Inhaled Acetaldehyde in Subjects with Allergic Rhinitis: Relationship to Methacholine Responsiveness
2002
<i>Background:</i> Asthmatic subjects have an exaggerated airway response to inhaled acetaldehyde, but no information is available on airway responsiveness to this bronchoconstrictor agent in subjects with allergic rhinitis. <i>Objective:</i> The aim of this study was to determine the effect of inhaled acetaldehyde on lung function in nonasthmatic subjects with allergic rhinitis. <i>Methods:</i> A total of 78 adults (43 subjects with allergic rhinitis, 16 asthmatics and 19 healthy subjects) were challenged with increased concentrations of acetaldehyde and methacholine. The response to each bronchoconstrictor agent was measured by the provocative concentra…
Systemic administration of D-penicillamine prevents the locomotor activation after intra-VTA ethanol administration in rats.
2010
Although recently published studies seem to confirm the important role displayed by acetaldehyde (ACH), the main metabolite of ethanol, in the behavioral effects of ethanol, the origin of ACH is still a matter of debate. While some authors confer more importance to the central (brain metabolism) origin of ACH, others indicate that the hepatic origin could be more relevant. In this study we have addressed this topic using an experimental approach that combines local microinjections of ethanol into the ventral tegmental area (VTA) (which guarantees the brain origin of the ACH) to induce motor activation in rats together with systemic administration (i.p.) of several doses (0, 12.5, 25 and 50 …
Alcohol addiction: a role for acetaldehyde
2009
Alcoholism is a chronically relapsing disorder characterized by cycles of repeated high alcohol intake and negative emotional consequences of withdrawal thought to contribute to excessive drinking and susceptibility to relapse. In the past years, the pharmacological and behavioural effects of alcohol, such us sedation, memory and learning impairment, were assigned to the main component of alcoholic drinks, ethanol. Recently acetaldehyde, the first metabolite of ethanol, seems to exert biological activity, besides its adverse effects. The aim of the present review is to elucidate the putative role of acetaldehyde in mediating the neuronal and behavioural features induced by ethanol intake.
Secondary brown carbon formation via the dicarbonyl imine pathway: nitrogen heterocycle formation and synergistic effects.
2016
Dicarbonyls are known to be important precursors of so-called atmospheric brown carbon, significantly affecting aerosol optical properties and radiative forcing. In this systematic study we report the formation of light-absorbing nitrogen containing compounds from simple 1,2-, 1,3-, 1,4-, and 1,5-dicarbonyl + amine reactions. A combination of spectrophotometric and mass spectrometric techniques was used to characterize reaction products in solutions mimicking atmospheric particulates. Experiments with individual dicarbonyls and dicarbonyl mixtures in ammonium sulfate and glycine solutions demonstrate that nitrogen heterocycles are common structural motifs of brown carbon chromophores formed…
Synthesis, characterization and X-ray structure of glycosyl-1,2-isoxazoles and glycosyl-1,2-isoxazolines prepared via 1,3-dipolar cycloaddition
2013
Abstract A convenient preparative method of a series of glycosyl-1,2-isoxazoles ( 6–11 ) and glycosyl-1,2-isoxazolines ( 15–20 ) by a simple and efficient 1,3-dipolar cycloaddition of a series of aryl nitrile oxide, generated in situ from aryl oximes ( 4–5 ), with a variety of O -propargyl glycosyles ( 1 – 3 ) or O -allyl glycosyles ( 12–14 ) respectively, is reported. The carbohydrate-containing 1,2-isoxazoles and 1,2-isoxazolines compounds were isolated in excellent yields (81–91%) and they were fully characterized by 1 H, 13 C NMR and mass spectrometry. The relative stereochemistry of the glycosyl-1,2-isoxazole 10 was confirmed by single crystal X-ray analysis. The molecular structure of…
Wine Consumption and Oral Cavity Cancer: Friend or Foe, Two Faces of Janus
2020
The health benefits of moderate wine consumption have been extensively studied during the last few decades. Some studies have demonstrated protective associations between moderate drinking and several diseases including oral cavity cancer (OCC). However, due to the various adverse effects related to ethanol content, the recommendation of moderate wine consumption has been controversial. The polyphenolic components of wine contribute to its beneficial effects with different biological pathways, including antioxidant, lipid regulating and anti-inflammatory effects. On the other hand, in the oral cavity, ethanol is oxidized to form acetaldehyde, a metabolite with genotoxic properties. This rev…