Search results for "ketone"
showing 10 items of 337 documents
Biological Profiling of Semisynthetic C19-Functionalized Ferruginol and Sugiol Analogues
2021
[EN] The abietane-type diterpenoids are significant bioactive compounds exhibiting a varied range of pharmacological properties. In this study, the first synthesis and biological investigation of the new abietane-diterpenoid (+)-4-epi-liquiditerpenoid acid (8a) together with several of its analogs are reported. The compounds were generated from the readily available methyl callitrisate (7), which was obtained from callitrisic acid present in Moroccan Sandarac resin. A biological evaluation was conducted to determine the effects of the different functional groups present in these molecules, providing basic structure-activity relationship (SAR) elements. In particular, the ferruginol and sugi…
Modelling Photoionisation in Isocytosine: Potential Formation of Longer‐Lived Excited State Cations in its Keto Form
2021
Abstract Studying the effects of UV and VUV radiation on non‐canonical DNA/RNA nucleobases allows us to compare how they release excess energy following absorption with respect to their canonical counterparts. This has attracted much research attention in recent years because of its likely influence on the origin of our genetic lexicon in prebiotic times. Here we present a CASSCF and XMS‐CASPT2 theoretical study of the photoionisation of non‐canonical pyrimidine nucleobase isocytosine in both its keto and enol tautomeric forms. We analyse their lowest energy cationic excited states including 2π+ , 2nO+ and 2nN+ and compare these to the corresponding electronic states in cytosine. Investigat…
Stereoelectronic Requirements for Optimal Hydrogen-Bond-Catalyzed Enolization
2011
Protein crystallographic analysis of the active sites of enolizing enzymes and structural analysis of hydrogen-bonded carbonyl compounds in small molecule crystal structures, complemented by quantum chemical calculations on related model enolization reactions, suggest a new stereoelectronic model that accounts for the observed out-of-plane orientation of hydrogen-bond donors (HBDs) in the oxyanion holes of enolizing enzymes. The computational results reveal that the lone-pair directionality of HBDs characteristic for hydrogen-bonded carbonyls is reduced upon enolization, and the enolate displays almost no directional preference for hydrogen bonding. Positioning the HBDs perpendicular to the…
Nuclear magnetic resonance spectroscopic study of beta-lactoglobulin interactions with two flavor compounds, gamma-decalactone and beta-ionone.
2002
Interactions between a well-characterized protein, beta-lactoglobulin, and two flavor compounds, beta-ionone and gamma-decalactone, were studied by 2D NMR spectroscopy. NMR spectra were recorded in aqueous solution (pH 2.0, 12 mM NaCl, 10% D(2)O) under conditions such that beta-lactoglobulin is present in a monomeric state. TOCSY and NOESY spectra were recorded on the protein and the complexes between protein and ligands. The spectra of the NH-CH(alpha) region showed the cross-signals due to the coupling between N- and C-bonded protons in the polypeptide backbone. The observed chemical shift variations in the presence of ligands can be assigned to changes in the protein conformation. It app…
Modelling Photoionisation in Isocytosine: Potential Formation of Longer‐Lived Excited State Cations in its Keto Form
2021
The front cover artwork is provided by Dr. Javier Segarra-Martí (University of Valencia, Spain) and Prof. Michael J. Bearpark (Imperial College London, UK). The image shows the ultrafast photoionisation of DNA canonical nucleobase cytosine and the slower ionization process in non-canonical base isocytosine embedded within a DNA backbone. Read the full text of the Article at 10.1002/cphc.202100402.
Photoreaction Between Benzoylthiophenes and N-BOC-Tryptophan Methyl Ester‡
2005
Drug-induced photoallergy requires as the first step formation of covalent drug-protein photoadducts. One of the key amino acids involved in this process is tryptophan (Trp). In this context, several diaryl ketones, including 2-benzoylthiophene (BT), [2-(5-benzoyl-5-thienyl)]-2-methylpropanoic methyl ester (TPA methyl ester) and 4-(2-thienylcarbonyl)phenyl]-2-methylpropanoic methyl ester (SUP methyl ester) have been irradiated in the presence of N-BOC-(L)-tryptophan methyl ester. Laser flash photolysis has allowed to detect three neutral radicals (ketyl, indolyl and skatolyl radicals) resulting from formal hydrogen-atom abstraction. This correlates well with the isolation of homodimers, as …
Enantioselective Mannich reaction of β-keto esters with aromatic and aliphatic imines using a cooperatively assisted bifunctional catalyst
2014
An efficient urea-enhanced thiourea catalyst enables the enantioselective Mannich reaction between β-keto esters and N-Boc-protected imines under mild conditions and minimal catalyst loading (1–3 mol %). Aliphatic and aromatic substituents are tolerated on both reaction partners, affording the products in good enantiomeric purity. The corresponding β-amino ketones can readily be accessed via decarboxylation without loss of enantiomeric purity.
Origin and correction of the deviations in retention times at increasing flow rate with Chromolith columns.
2010
Chromoliths can be used at flow rates beyond those feasible for conventional microparticulate packed columns. Ideally, the plots of the retention time versus the inverse of delivered flow rate should exhibit y-intercept of zero. However, significant positive deviations correlating with the solute polarity were observed for several compounds chromatographed with a Chromolith column, owing to the increased system pressure. Consequently, the dead time marker exhibits a smaller deviation, making the retention factors depend on the flow rate. Chromoliths are made of a silica-based monolith encapsulated within a PEEK tube, and should suffer larger stress with pressure than stainless steel columns…
Medium-chain triglycerides may improve memory in non-demented older adults: a systematic review of randomized controlled trials
2022
Abstract Background Ketosis has been exploited for its neuroprotective impact and treatment of neurological conditions via ketone production. Exogenous medium-chain triglyceride (MCT) supplementation may induce nutritional ketosis. The aim of this systematic review is to explore the effects of MCTs on memory function in older adults without cognitive impairment. Methods A systematic literature search of PubMed, Cochrane Library, Scopus, and Web of Science was employed from inception until April 2022 for randomized controlled trials (RCTs) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, investigating the impact of MCT oils on com…
Resource or waste? A perspective of plastics degradation in soil with a focus on end-of-life options.
2018
‘Capable-of-being-shaped’ synthetic compounds are prevailing today over horn, bone, leather, wood, stone, metal, glass, or ceramic in products that were previously left to natural materials. Plastic is, in fact, economical, simple, adaptable, and waterproof. Also, it is durable and resilient to natural degradation (although microbial species capable of degrading plastics do exist). In becoming a waste, plastic accumulation adversely affects ecosystems. The majority of plastic debris pollutes waters, accumulating in oceans. And, the behaviour and the quantity of plastic, which has become waste, are rather well documented in the water, in fact. This review collects existing information on pla…