Search results for "Stereoisomerism"
showing 10 items of 453 documents
Cis- and trans molybdenum oxo complexes of a prochiral tetradentate aminophenolate ligand : Synthesis, characterization and oxotransfer activity
2020
Abstract Reaction of [MoO2Cl2(dmso)2] with the tetradentate O2N2 donor ligand papy [H2papy = N-(2-hydroxybenzyl)-N-(2-picolyl)glycine] leads to formation of the dioxomolybdenum(VI) complex [MoO2(papy)] (1) as a mixture of cis and trans isomers. Recrystallization from methanol furnishes solid cis-1, whereas the use of a dichloromethane-hexane mixture allows for the isolation of the trans-1 isomer. Both isomers have been structurally characterized by X-ray crystallography and the energy difference between the isomeric pair has been investigated by electronic structure calculations. Optimization of two configurational isomers in the gas phase predicts the trans isomer to lie 2.5 kcal/mol lower…
Artemisia arborescens essential oil composition, enantiomeric distribution and antimicrobial activity from different wild populations from the Medite…
2016
International audience; Aerial parts of Artemisiaarborescens were collected from different sites of the Mediterranean area (southwestern Algeria and southern Italy) and the chemical composition of their essential oil (EO) extracted by hydrodistillation was studied by both gas chromatography (GC) equipped with an enantioselective capillary column and GC/mass spectrometry (GC/MS). The EOs obtained were tested against several Listeriamonocytogenes strains. Using GC and GC/MS, 41 compounds were identified, accounting for 96.0-98.8% of the total EO. All EOs showed a similar terpene profile, which was rich in chamazulene, -thujone, and camphor. However, the concentration of such compounds varied …
Development of Novel Peptide-Based Michael Acceptors Targeting Rhodesain and Falcipain-2 for the Treatment of Neglected Tropical Diseases (NTDs)
2017
This paper describes the development of a class of peptide-based inhibitors as novel antitrypanosomal and antimalarial agents. The inhibitors are based on a characteristic peptide sequence for the inhibition of the cysteine proteases rhodesain of Trypanosoma brucei rhodesiense and falcipain-2 of Plasmodium falciparum. We exploited the reactivity of novel unsaturated electrophilic functions such as vinyl-sulfones, -ketones, -esters, and -nitriles. The Michael acceptors inhibited both rhodesain and falcipain-2, at nanomolar and micromolar levels, respectively. In particular, the vinyl ketone 3b has emerged as a potent rhodesain inhibitor (k2nd = 67 × 106 M-1 min-1), endowed with a picomolar b…
Highly effective, regiospecific reduction of chalcone by cyanobacteria leads to the formation of dihydrochalcone: two steps towards natural sweetness
2017
Abstract Background Chalcones are the biogenetic precursors of all known flavonoids, which play an essential role in various metabolic processes in photosynthesizing organisms. The use of whole cyanobacteria cells in a two-step, light-catalysed regioselective bio-reduction of chalcone, leading to the formation of the corresponding dihydrochalcone, is reported. The prokaryotic microalgae cyanobacteria are known to produce phenolic compounds, including flavonoids, as natural components of cells. It seems logical that organisms producing such compounds possess a suitable “enzymatic apparatus” to carry out their biotransformation. Therefore, determination of the ability of whole cells of select…
Anti-herpetic and anti-dengue activity of abietane ferruginol analogues synthesized from (+)-dehydroabietylamine
2015
The abietane-type diterpenoid (+)-ferruginol (1), a bioactive compound isolated from several plants, has attracted much attention as consequence of its pharmacological properties, which includes antibacterial, antifungal, antimicrobial, cardioprotective, anti-oxidative, anti-plasmodial, leishmanicidal, anti-ulcerogenic, anti-inflammatory and antitumor actions. In this study, we report on the antiviral evaluation of ferruginol (1) and several analogues synthesized from commercial (+)-dehydroabietylamine. Thus, the activity against Human Herpesvirus type 1, Human Herpesvirus type 2 and Dengue Virus type 2, was studied. Two ferruginol analogues showed high antiviral selectivity index and reduc…
Diastereoselectivity of 5-Methyluridine Osmylation Is Inverted inside an RNA Chain
2016
In this study, we investigated the reaction of the osmium tetroxide-bipyridine complex with pyrimidines in RNA. This reagent, which reacts with the diastereotopic 5-6 double bond, thus leading to the formation of two diastereomers, was used in the past to label thymidine and 5-methylcytosine in DNA. In light of the growing interest in post-transcriptional RNA modifications, we addressed the question of whether this reagent could be used for labeling of the naturally occurring RNA modifications 5-methylcytosine and 5-methyluridine. On nucleoside level, 5-methylcytosine and 5-methyluridine revealed a 5- and 12-fold preference, respectively, over their nonmethylated equivalents. Performing the…
Functional differences between l- and d-carnitine in metabolic regulation evaluated using a low-carnitine Nile tilapia model.
2019
Abstractl-Carnitine is essential for mitochondrialβ-oxidation and has been used as a lipid-lowering feed additive in humans and farmed animals.d-Carnitine is an optical isomer ofl-carnitine anddl-carnitine has been widely used in animal feeds. However, the functional differences betweenl- andd-carnitine are difficult to study because of the endogenousl-carnitine background. In the present study, we developed a low-carnitine Nile tilapia model by treating fish with a carnitine synthesis inhibitor, and used this model to investigate the functional differences betweenl- andd-carnitine in nutrient metabolism in fish.l- ord-carnitine (0·4 g/kg diet) was fed to the low-carnitine tilapia for 6 wee…
Stereochemical features of the hydrolysis of 9,10-epoxystearic acid catalysed by plant and mammalian epoxide hydrolases
2002
cis-9,10-Epoxystearic acid was used as a tool to probe the active sites of epoxide hydrolases (EHs) of mammalian and plant origin. We have compared the stereochemical features of the hydrolysis of this substrate catalysed by soluble and membrane-bound rat liver EHs, by soluble EH (purified to apparent homogeneity) obtained from maize seedlings or celeriac roots, and by recombinant soybean EH expressed in yeast. Plant EHs were found to differ in their enantioselectivity, i.e. their ability to discriminate between the two enantiomers of 9,10-epoxystearic acid. For example, while the maize enzyme hydrated both enantiomers at the same rate, the EH from soybean exhibited very high enantioselecti…
Chiral Serum Pharmacokinetics of 4-Fluoroamphetamine after Controlled Oral Administration
2021
Abstract Over the last two decades, misuse of 4-fluoroamphetamine (4-FA) became an emerging issue in many European countries. Stimulating effects last for 4–6 hours and can impact psychomotor performance. The metabolism of amphetamine-type stimulants is stereoselective and quantification of (R)- and (S)-enantiomers has been suggested for assessing time of use. To date, no data on enantioselective pharmacokinetics is available for 4-FA in serum samples. An enantioselective liquid chromatography−tandem mass spectrometry (LC–MS-MS) method was developed using a chiral Phenomenex® Lux 3 μm AMP column. Validation of the method showed satisfactory selectivity, sensitivity, linearity (0.5–250 ng/mL…
Reversed phase liquid chromatography for the enantioseparation of local anaesthetics in polysaccharide-based stationary phases. Application to biodeg…
2020
[EN] A comprehensive study on the chiral separation of bupivacaine, mepivacaine, prilocaine and propanocaine with eight commercial polysaccharide-based chiral stationary phases (CSPs) in reversed phase conditions compatible with MS detection is performed. Methanol and acetonitrile are used as organic modifiers. Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared. The polysaccharide-based CSPs tested present different enantioselectivity towards the analytes. From the results, the experimental conditions for determining the enantiomers of bupivacaine, mepivacaine, prilocaine and propanocaine in saline aqueous samples using MS detecti…