Search results for "iOS"

Enantiomeric Resolution of Asymmetric-Carbon-Free Binuclear Double-Stranded Cobalt(III) Helicates and Their Application as Catalysts in Asymmetric Re…

2018

A series of double-stranded binuclear helicates [Co2(H1)2]4+, [Co2(H2)2]4+, and [Co2(H3)2]4+, derived from monodeprotonated bis-pyridyl hydrazine-based ligands of H21, H22, and H23 with one, two, and three -CH2 spacers, were obtained. These asymmetric-carbon-free racemic helicates were separated into their ΔΔ and ΛΛ enantiomers. The resolved helicates were examined for the first time as enantioselective catalysts in asymmetric benzoylation and nitroaldol reactions.

Efficient and simple synthesis of novel 1,2,3-triazolyl-linked benzimidazolone, molecular docking and evaluation of their antimicrobial activity

2020

In this study, a novel series of 1,2,3-triazolyl-benzimidazolone derivatives have been synthesized by click reaction of azides with benzimidazolones 2a–b. The latter compounds were prepared with excellent yields (85–97%), the structures of products were determined by spectral analysis. Then, the X-rays crystallographic analysis of compound 7a revealed the self-assembling properties. The new heterocycles were evaluated for their in vitro antimicrobial activities against Gram-positive and Gram-negative bacteria and against fungi strains. The most tested synthesized compounds showed potent antibacterial and antifungal activities against all tested strains. The compound 6c was found to be the m…

Thiourea-Catalyzed Domino Michael–Mannich [3+2] Cycloadditions: A Strategy for the Asymmetric Synthesis of 3,3′-Pyrrolidinyl-dispirooxindoles

2017

The asymmetric synthesis of trifluoromethylated 3,3′-pyrrolidinyl-dispirooxindole derivatives with four contiguous stereogenic centers, including two vicinal spiro-stereocenters, is described. Employing a bifunctional thiourea catalyst, a domino Michael–Mannich [3+2] cycloaddition occurs readily between isatin ketimines and isatin-derived enoates with good yields and very high stereoselectivities, providing a direct entry to the title compounds of potential medical value.

Organocatalytic Asymmetric Synthesis of 2,3′-Connected Bis-Indolinones by Mannich Reactions of N-Acetylindolin-3-ones with Isatin N-Boc Ketimines

2017

A highly diastereo- and enantioselective Mannich reaction of N-acetylindolin-3-ones with isatin N-Boc ketimines to form 2,3′-connected bis-indolinones is developed employing a low loading of a readily available bifunctional thiourea catalyst. The asymmetric synthesis connects two indolinones via a vic-diamine unit and generates two neighboring stereocenters.

Catalytic enantioselective aza-Reformatsky reaction with seven-membered cyclic imines dibenzo[b,f][1,4]oxazepines

2017

A catalytic enantioselective aza-Reformatsky reaction is reported with cyclic dibenzo[b,f][1,4]oxazepines and ethyl iodoacetate leading to the synthesis of chiral ethyl 2-(10,11-dihydrodibenzo[b,f][1,4]oxazepin-11-yl)acetate derivatives with excellent yields and high enantioselectivities (up to 98% yield and 97 : 3 er) using a readily available diaryl prolinol L4 as the chiral ligand and Me2Zn as the zinc source under an air atmosphere. Furthermore, different transformations were carried out with the corresponding chiral β-amino esters, preserving in all cases the optical purity.

Catalytic Asymmetric Reactions Involving the Seven-Membered Cyclic Imine Moieties Present in Dibenzo[b,f][1,4]oxazepines

2017

The dibenzo[b,f][1,4]oxazepine scaffold is a privileged structure in medicinal chemistry that displays a wide variety of biological and pharmacological activities. However, catalytic asymmetric methodologies for the synthesis of chiral dibenzo[b,f][1,4]oxazepine derivatives are scarce in the literature. This microreview presents an overview of enantioselective reactions in which these cyclic seven-membered imines are used as electrophiles, including their substrate scope, limitations and application to the synthesis of related compounds.

2019

Abstract. This study uses the synergy of multi-resolution soil moisture (SM) satellite estimates from the Soil Moisture Ocean Salinity (SMOS) mission, a dense network of ground-based SM measurements, and a soil–vegetation–atmosphere transfer (SVAT) model, SURFEX (externalized surface), module ISBA (interactions between soil, biosphere and atmosphere), to examine the benefits of the SMOS level 4 (SMOS-L4) version 3.0, or “all weather” high-resolution soil moisture disaggregated product (SMOS-L43.0; ∼1 km). The added value compared to SMOS level 3 (SMOS-L3; ∼25 km) and SMOS level 2 (SMOS-L2; ∼15 km) is investigated. In situ SM observations over the Valencia anchor station (VAS; SMOS calibrati…

Cosmic-Ray Anisotropies in Right Ascension Measured by the Pierre Auger Observatory

2020

We present measurements of the large-scale cosmic-ray anisotropies in right ascension, using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 years. We determine the equatorial dipole component, ~d⊥, through a Fourier analysis in right ascension that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the “East-West” method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser sub-array of detectors with 750 m separation, which allows us to extend …

A Search for Ultra-high-energy Neutrinos from TXS 0506+056 Using the Pierre Auger Observatory

2020

Results of a search for ultra-high-energy neutrinos with the Pierre Auger Observatory from the direction of the blazar TXS 0506+056 are presented. They were obtained as part of the follow-up that stemmed from the detection of high-energy neutrinos and gamma rays with IceCube, Fermi-LAT, MAGIC, and other detectors of electromagnetic radiation in several bands. The Pierre Auger Observatory is sensitive to neutrinos in the energy range from 100 PeV to 100 EeV and in the zenith-angle range from θ = 60° to θ = 95°, where the zenith angle is measured from the vertical direction. No neutrinos from the direction of TXS 0506+056 have been found. The results were analyzed in three periods: One of 6 m…

Changements environnementaux survenant à la limite Oligocène/Miocène du bassin des Limagnes (Massif central, France).

2018

16 pages; International audience; Continental environments are very sensitive to climatic variations. A unique opportunity to study the climate changes around the Oligocene/Miocene boundary is offered by the Limagne graben Basin (France) where this stage boundary is well constrained by fossils. Indeed, some localities of the Limagne Graben Basin are so rich in mammal remains that they have become a European reference for mammal biostratigraphy. The dominant sedimentary facies of the lacustrine deposits in the northern part of the Limagne Graben Basin are composed of poorly cemented marls and calcarenites containing various plants and animals remains (e.g. algae, fish bones and teeth, gastro…