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81.
Stéphane Laval Wissam Dayoub Leyla Pehlivan Estelle Métay Dominique Delbrayelle Gérard Mignani Marc Lemaire 《Tetrahedron letters》2014
A simple and convenient method for the chemoselective reduction of nitriles into aldehydes using a 1,1,3,3-tetramethyldisiloxane (TMDS)/triisopropoxyvanadium(V) oxide reducing system is described. Aromatic as well as aliphatic nitriles are reduced into the corresponding aldehydes in moderate to good yields. 相似文献
82.
5‐O‐Caffeoylshikimic acid from Solanum somalense leaves: Advantage of centrifugal partition chromatography over conventional column chromatography
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Saïda Chideh Serge Pilard Jacques Attoumbré Robert Saguez Alshaimaa Hassan‐Abdallah Dominique Cailleu Anne Wadouachi Sylvie Baltora‐Rosset 《Journal of separation science》2014,37(17):2331-2339
Solanum somalense leaves, used in Djibouti for their medicinal properties, were extracted by MeOH. Because of the high polyphenol and flavonoid contents of the extract, respectively, determined at 80.80 ± 2.13 mg gallic acid equivalent/g dry weight and 24.4 ± 1.01 mg quercetin equivalent/g dry weight, the isolation and purification of the main polyphenols were carried out by silica gel column chromatography and centrifugal partition chromatography. Column chromatography led to 11 enriched fractions requiring further purification, while centrifugal partition chromatography allowed the easy recovery of the main compound of the extract. In a solvent system composed of CHCl3/MeOH/H2O (9.5:10:5), 21.8 mg of this compound at 97% purity was obtained leading to a yield of 2.63%. Its structure was established as 5‐O‐caffeoylshikimic acid by mass spectrometry and NMR spectroscopy. This work shows that S. somalense leaves contain very high level of 5‐O‐caffeoylshikimic acid (0.74% dry weight), making it a potential source of production of this secondary metabolite that is not commonly found in nature but could be partly responsible of the medicinal properties of S. somalense leaves. 相似文献
83.
84.
Abdirahman Elmi Fatouma Mohamed Abdoul-Latif Rosella Spina Franois Dupire Stphanie Philippot Champy Marie-France Hugues Jacobs Dominique Laurain-Mattar 《Molecules (Basel, Switzerland)》2021,26(10)
For the first time, the study of the antioxidant activity, the characterization of the phytoconstituants, and the evaluation of in vitro and in vivo toxicity of A. djiboutiensis leave and latex are performed. The antioxidant activity of both latex (ADL) and the methanolic extract of leaves (ADM) is determined using 1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging radical methods and ferric reducing/antioxidant power (FRAP) assay. The phytochemical study of latex is done using Liquid Chromatography-Mass Spectrometry (LC-MS/MS) and a molecular networking-based approach. The evaluation of in vivo toxicity is performed on mice by oral gavage with a suspension of ADL. Our results show that weak antioxidant activity of ADL and ADM in opposition to their high polyphenol, 83.01 mg and 46.4 mg expressed in gallic acid equivalent (GAE)/g of dry weight (DW), respectively, and flavonoid contents 13.12 mg and 4.25 mg expressed in quercetin equivalent (QE)/g dry weight (DW), respectively. Using the Global Natural Products Social Molecular Networking (GNPS) website, nine (9) anthraquinones derivatives, ten (10) chromones derivatives, two (2) flavonols/ chromones isomers are annotated in the molecular network. The treated mice do not display abnormalities in their general physical appearance and biochemistry parameters, compared to the controls. Only glucose and calcium levels are slightly higher in male treated mice compared to the vehicles. 相似文献
85.
We present here the first 3D homonuclear/heteronuclear correlation experiment applied to quadrupolar nuclei and making use of the sole scalar J-coupling. This experiment, based on the 2D-Homonuclear-Heteronuclear Single Quantum Correlation (H-HSQC) experiment, uses a relayed transfer from the (27)Al central transition to neighbouring (31)P spins and to the central transition of a second (27)Al. It confirms the correlation map characterizing the two (27)Al and the (31)P NMR signatures of (27)Al-O-(31)P-O-(27)Al chemically bonded molecular motifs. 相似文献
86.
Dominique Fellah 《Letters in Mathematical Physics》2007,80(2):101-113
87.
Titanium‐Catalyzed Hydroalumination of Conjugated Dienes: Access to Fulvene‐Derived Allylaluminium Reagents and Their Diastereoselective Reactions with Carbonyl Compounds
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Dr. Jomy Joseph Dr. Florian Jaroschik Dr. Dominique Harakat Dr. K. V. Radhakrishnan Dr. Jean‐Luc Vasse Prof. Jan Szymoniak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5433-5438
The described titanium‐catalyzed hydroalumination of conjugated dienes opens up a new way to allylaluminium reagents. The reaction is carried out by using diisobutylaluminium hydride (DIBAL‐H) and a catalytic amount of [Cp2TiCl2] (Cp=cyclopentadienyl). When applied to mono‐ and disubstitued pentafulvenes, this reaction proceeds in a highly endocyclic manner. The formed allylaluminium compounds react regio‐ and stereoselectively with both aldehydes and ketones to afford homoallylic alcohols that are suitable synthons for functionalized cyclopentanones. An extension of this methodology to simple dienes was also investigated. In the proposed mechanism, the initially formed bimetallic species (Ti/Al) are involved in the two possible catalytic cycles with a direct hydroalumination or/and a hydrotitanation followed by a titanium to aluminium transmetallation. 相似文献
88.
Karol Kulasinski Sinan Keten Sergey V. Churakov Dominique Derome Jan Carmeliet 《Cellulose (London, England)》2014,21(3):1103-1116
The quintessential form of cellulose in wood consists of microfibrils that have high aspect ratio crystalline domains embedded within an amorphous cellulose domain. In this study, we apply united-atom molecular dynamics simulations to quantify changes in different morphologies of cellulose. We compare the structure of crystalline cellulose with paracrystalline and amorphous phases that are both obtained by high temperature equilibration followed by quenching at room temperature. Our study reveals that the paracrystalline phase may be an intermediate, kinetically arrested phase formed upon amorphisation of crystalline cellulose. The quenched structures yield isotropic amorphous polymer domains consistent with experimental results, thereby validating a new computational protocol for achieving amorphous cellulose structure. The non-crystalline cellulose compared to crystalline structure is characterized by a dramatic decrease in elastic modulus, thermal expansion coefficient, bond energies, and number of hydrogen bonds. Analysis of the lattice parameters shows that Iβ cellulose undergoes a phase transition into high-temperature phase in the range of 450–550 K. The mechanisms of the phase transition elucidated here present an atomistic view of the temperature dependent dynamic structure and mechanical properties of cellulose. The paracrystalline state of cellulose exhibits intermediate mechanical properties, between crystalline and amorphous phases, that can be assigned to the physical properties of the interphase regions between crystalline and amorphous cellulose in wood microfibrils. Our results suggest an atomistic structural view of amorphous cellulose which is consistent with experimental data available up to date and provide a basis for future multi-scale models for wood microfibrils and all-cellulose nanocomposites. 相似文献
89.
90.
Shengdong Wang Rgis Guillot Jean‐Franois Carpentier Yann Sarazin Christophe Bour Vincent Gandon David Lebuf 《Angewandte Chemie (International ed. in English)》2020,59(3):1134-1138
Herein, we report the preparation of bridged tetrahydrobenzo[b]azepines, which was accomplished through an aza‐Piancatelli cyclization/Michael addition sequence in a one‐pot fashion from readily available precursors. It is noteworthy that a general method to access these scaffolds was hitherto unprecedented. Additionally, the multifaceted aspects of this process have been exemplified through its application to the synthesis of 2‐azabicyclo[3.2.1]octanes and bridged tetrahydrobenzo[b]oxepines, along with post‐derivatizations. 相似文献