Search results for "iOS"
showing 10 items of 8115 documents
A Combination of Visible-Light Organophotoredox Catalysis and Asymmetric Organocatalysis for the Enantioselective Mannich Reaction of Dihydroquinoxal…
2019
[EN] An enantioselective photooxidative Mannich reaction of dihydroquinoxalinones with ketones by the merger of organophotoredox and asymmetric organocatalysis is described. This protocol features very mild reaction conditions using simple and cheap catalysts (Eosin Y and (S)-Proline) for the synthesis of chiral quinoxaline derivatives with good to high yields (up to 94%) and excellent enantioselectivities (up to 99% ee).
dIvergEnt: How IgE Axis Contributes to the Continuum of Allergic Asthma and Anti-IgE Therapies
2017
[EN] Asthma is an airway disease characterised by chronic inflammation with intermittent or permanent symptoms including wheezing, shortness of breath, chest tightness, and cough, which vary in terms of their occurrence, frequency, and intensity. The most common associated feature in the airways of patients with asthma is airway inflammation. In recent decades, efforts have been made to characterise the heterogeneous clinical nature of asthma. The interest in improving the definitions of asthma phenotypes and endotypes is growing, although these classifications do not always correlate with prognosis nor are always appropriate therapeutic approaches. Attempts have been made to identify the m…
Higher serum levels of periostin and the risk of exacerbations in moderate asthmatics
2016
BACKGROUND: In asthma, exacerbations and poor disease control are linked to airway allergic inflammation. Serum periostin has been proposed as a systemic biomarker of eosinophilic inflammation. This pilot study aims at evaluating whether in patients with moderate asthma, higher baseline levels of serum periostin are associated with a greater risk of exacerbation. METHODS: Fifteen outpatients with moderate allergic asthma were recruited. Serum concentrations of periostin were assessed (ELISA) at baseline, and the frequency of asthma exacerbations was recorded during a one-year follow-up. RESULTS: Patients (M/F: 10/5, mean age of 47.6 ± 11.0 years) had mean ACQ score of 5.5 ± 4.2 and FEV1%pre…
Allium makrianum (Alliaceae), a new autumnal species from Greece
2010
Allium makrianum is described as a new species growing on the limestone of the Chios, north-eastern Aegean island (Greece). It is a very rare autumnal geophyte, showing some relationship with A. archeotrichon from Rhodos. Its iconography, morphology, chromosome number (2n=16), leaf anatomy, ecology and taxonomy are examined.
Stereoselective synthesis of the naturally occurring 2-pyranone dodoneine
2008
The first total synthesis of the naturally occurring dihydropyranone dodoneine is reported. Asymmetric allylation reactions were used for the stereoselective generation of the two stereogenic centers. The pyranone ring was created by ring-closing metathesis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Recent advances in the synthesis of functionalised monofluorinated compounds.
2018
Over the past few years, we have tackled the synthesis of interesting monofluorinated organic molecules, such as: dihydronaphthalene derivatives, β-fluoro sulfones and related carbonyl compounds, fluorohydrins and allylic alcohols. Overall, a wide range of modern synthetic techniques are covered in this feature article including transition-metal, photo- and organocatalysis, nucleophilic and electrophilic fluorinations, chiral auxiliaries and enantioselective catalysis.
New approaches to the synthesis of organofluorine nitrogenated derivatives
2004
Fluorinated carboxylic acids are valuable building blocks for several types of organofluorine nitrogenated derivatives. In this review paper, several strategies that use these compounds as starting materials are described. First, fluorinated seven-membered cyclic β-amino esters can be diastereoselectively synthesized from these compounds with a ring-closing metathesis (RCM) reaction as the key step. The use of the RCM reaction in a different approach enables the preparation of fluorinated cyclic α-amino acid derivatives. Fluorinated carboxylic acids also constitute the starting material for the asymmetric synthesis of fluorinated allylic amines. Finally, a solution and solid-phase synthesis…
Diastereoselective synthesis of antiquorin and related polyoxygenated atisene-type diterpenes
2007
Abstract A diastereoselective approach to polyoxygenated atisene-type diterpenes starting from (S)-(+)-carvone is described. The key steps used in the preparation of the atisene framework are an intramolecular Diels–Alder reaction, an intramolecular diazoketone cyclopropanation, an endocyclic cyclopropane ring cleavage and the regioselective reduction of an allylic bromide by a low-valent chromium species. The synthesis of natural atisanes antiquorin (1), atis-16-ene-3,14-dione (3), atis-16-ene-2,3,14-trione (8) and 3β-hydroxy-atis-16-ene-2,14-dione (9) following this approach is presented. Also described is the synthesis of 18-hydroxy-atis-16-ene-3,14-dione (5), the structure erroneously a…
Novel Approach for Asymmetric Synthesis of Fluorinated β-Amino Sulfones and Allylic Amines
2003
[reaction: see text] Enantiomerically pure gamma-fluoroalkyl beta-amino sulfones are readily synthesized in three steps starting from fluorinated imidoyl chlorides and arylmethyl sulfones. A complementary two-step sequence starting from chiral fluorinated beta-amino sulfoxides has also been developed. To illustrate the application of this procedure, a new method for the synthesis of alpha-fluoroalkyl allylic amines in optically pure form involving a Julia methylenation-desulfonylation reaction is presented.
Investigation of the aqueous transmetalation of π-allylpalladium with indium salt: the use of the Pd(OAc)2–TPPTS catalyst
2005
pi-Allylpalladium complexes could be generated in water by the palladium(0) water soluble catalyst prepared in situ from palladium acetate and TPPTS. These complexes were transmetalated with indium to react with benzaldehyde. The aqueous solution of Pd(0)(TPPTS)(n) could be reused without deterioration of the catalyst in the first and second recycling. The system proved to be efficient with primary and secondary allylic substrates. The stereochemical outcome of the allylation through umpolung of allylpalladium, was also studied using models with a restraint conformation.