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81.
Pierre Quinodoz Alexandre Lumbroso Mathilde Lachia Claudio Screpanti Stefano Rendine Beyza Horoz Mert Bozoflu Saron Catak Raymonde Fonné-Pfister Katrin Hermann Alain De Mesmaeker 《Helvetica chimica acta》2023,106(1):e202200145
Strigolactones (SLs) are signaling molecules involved in plant development and governing interactions with soil microorganisms in the rhizosphere as well as the germination of parasitic weeds. Developing their use in Crop Protection is a promising approach to a sustainable agriculture by mitigating biotic and abiotic stresses. Recently, a new class of lactam analogues of SL has emerged, namely strigolactams, displaying outstanding potency to induce the germination of parasitic weed O. cumana as well as enhanced chemical and soil stability. Herein, we describe the stereoselective synthesis of GR24 and GR18 lactams harnessing the chemistry of chiral keteniminium (KI) salts, in particular the unprecedented reactivity of chloro-substituted KI, supported by DFT calculations. We disclose subsequently the biological activity on corn of the 32 stereopure strigolactams prepared, highlighting the crucial influence of stereochemistry and lactam substitution, rationalized by docking analyses. Finally, we performed stability studies in soil, which reveal that stereoisomers display very different half-lives, reflecting the significant impact of stereochemistry on degradation kinetics. 相似文献
82.
Marie-Louisa Ramaroson Claude Koutouan Jean-Jacques Helesbeux Valrie Le Clerc Latifa Hamama Emmanuel Geoffriau Mathilde Briard 《Molecules (Basel, Switzerland)》2022,27(23)
Phenylpropanoids and flavonoids are specialized metabolites frequently reported as involved in plant defense to biotic or abiotic stresses. Their biosynthetic accumulation may be constitutive and/or induced in response to external stimuli. They may participate in plant signaling driving plant defense responses, act as a physical or chemical barrier to prevent invasion, or as a direct toxic weapon against microbial or insect targets. Their protective action is described as the combinatory effect of their localization during the host’s interaction with aggressors, their sustained availability, and the predominance of specific compounds or synergy with others. Their biosynthesis and regulation are partly deciphered; however, a lot of gaps in knowledge remain to be filled. Their mode of action on microorganisms and insects probably arises from an interference with important cellular machineries and structures, yet this is not fully understood for all type of pests and pathogens. We present here an overview of advances in the state of the art for both phenylpropanoids and flavonoids with the objective of paving the way for plant breeders looking for natural sources of resistance to improve plant varieties. Examples are provided for all types of microorganisms and insects that are targeted in crop protection. For this purpose, fields of phytopathology, phytochemistry, and human health were explored. 相似文献
83.
Mathilde Laird Carole Carcel Masafumi Unno John R. Bartlett Michel Wong Chi Man 《Molecules (Basel, Switzerland)》2022,27(22)
Herein, we report synthetic strategies for the development of a bifunctional Janus T4 tetrapod (Janus ring), in which the orthogonal silsesquioxane and organic faces are independently functionalized. An all-cis T4 tetrasilanolate was functionalized to introduce thiol moieties on the silsesquioxane face and naphthyl groups on the organic face to introduce luminescent and self-organization properties. The stepwise synthesis conditions required to prepare such perfectly defined oligomers via a suite of well-defined intermediates and to avoid polymerization or reactions over all eight positions of the tetrapod are explored via 29Si, 13C and 1H NMR, FTIR and TOF-ESI mass spectroscopy. To the best of our knowledge, this is one of the few reports of Janus T4 tetrapods, with different functional groups located on both faces of the molecule, thus expanding the potential range of applications for these versatile precursors. 相似文献
84.
G. M. Abakarov M.-Z. V. Vagabov V. A. Pantin I. D. Sadekov V. I. Minkin 《Chemistry of Heterocyclic Compounds》2007,43(8):1076-1080
N-methyl-2-phenylbenzotellurazolinium iodide, like other N-methylbenzochalcogenazolium salts, readily undergoes reduction,
hydrolysis, and recyclization with hydrazine hydrate and o-phenylene diamine. 1-Methyl-2-phenylbenzotelluronioazole perchlorate
is an effective methylating agent in reactions with nucleophiles.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1268–1272, August, 2007. 相似文献
85.
Mathilde Semenkoff 《Optics and Lasers in Engineering》1992,17(3-5):179-186
Curvature of a multimode optical fiber reduces the number of modes propagating through the fiber and thus the light power at the fiber output. In this paper we study this phenomenon and use it to make a new intrinsic temperature sensor, which operates by a local refractive index variation of the constituent material as a function of both temperature and curvature. The sensing effect comes from an organized competition between a predetermined strain obtained by bending the fiber with a known bending radius and a temperature-indiced strain that will modulate the waveguide. This sensor measures to an accuracy of 0°1C. 相似文献
86.
Pieroni O Plaza P Mahet M Angelini N Checcucci G Malatesta M Martin MM Lenci F 《Photochemistry and photobiology》2005,81(6):1343-1346
Circular dichroism (CD) was used to study the structure of oxyblepharismin (OxyBP), the photoreceptor chromophore for the photophobic response of the blue form of Blepharisma japonicum. Both the chromophore associated to its native protein and the free chromophore in ethanol solution were investigated. CD spectra in the far-UV range indicate that OxyBP induces a slight increase in the alpha-helix content of the protein matrix. CD spectra in the near-UV and visible region of the spectrum show that OxyBP adopts a chiral conformation with a preferential geometry not only when associated to its protein matrix, but also when isolated and dissolved in ethanol. This experimental result is related to the existence of a high-energy interconversion barrier between two enantiomeric structures of the molecule and discussed on the basis of an asymmetric biosynthesis of its precursor, blepharismin. 相似文献
87.
Dr. Andrea Capozzi M. Sc. Saket Patel M. Sc. Christine Pepke Gunnarsson Dr. Irene Marco‐Rius Dr. Arnaud Comment Dr. Magnus Karlsson Dr. Mathilde H. Lerche Dr. Olivier Ouari Prof. Jan Henrik Ardenkjær‐Larsen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1348-1353
Free radicals generated by UV‐light irradiation of a frozen solution containing a fraction of pyruvic acid (PA) have demonstrated their dissolution dynamic nuclear polarization (dDNP) potential, providing up to 30 % [1‐13C]PA liquid‐state polarization. Moreover, their labile nature has proven to pave a way to nuclear polarization storage and transport. Herein, differently from the case of PA, the issue of providing dDNP UV‐radical precursors (trimethylpyruvic acid and its methyl‐deuterated form) not involved in any metabolic pathway was investigated. The 13C dDNP performance was evaluated for hyperpolarization of [U‐13C6,1,2,3,4,5,6,6‐d7]‐d ‐glucose. The generated UV‐radicals proved to be versatile and highly efficient polarizing agents, providing, after dissolution and transfer (10 s), a 13C liquid‐state polarization of up to 32 %. 相似文献
88.
Charles Audet Andrew R. Conn Sébastien Le Digabel Mathilde Peyrega 《Computational Optimization and Applications》2018,71(2):307-329
We study derivative-free constrained optimization problems and propose a trust-region method that builds linear or quadratic models around the best feasible and around the best infeasible solutions found so far. These models are optimized within a trust region, and the progressive barrier methodology handles the constraints by progressively pushing the infeasible solutions toward the feasible domain. Computational experiments on 40 smooth constrained problems indicate that the proposed method is competitive with COBYLA, and experiments on two nonsmooth multidisciplinary optimization problems from mechanical engineering show that it can be competitive with the NOMAD software. 相似文献
89.
Mathilde Fournire Gilles Bedoux Djouhar Souak Nathalie Bourgougnon Marc G. J. Feuilloley Thomas Latire 《Molecules (Basel, Switzerland)》2021,26(16)
Ulva sp. is known to be a source of bioactive compounds such as ulvans, but to date, their biological activity on skin commensal and/or opportunistic pathogen bacteria has not been reported. In this study, the effects of poly- and oligosaccharide fractions produced by enzyme-assisted extraction and depolymerization were investigated, for the first time in vitro, on cutaneous bacteria: Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes. At 1000 μg/mL, poly- and oligosaccharide fractions did not affect the growth of the bacteria regarding their generation time. Polysaccharide Ulva sp. fractions at 1000 μg/mL did not alter the bacterial biofilm formation, while oligosaccharide fractions modified S. epidermidis and C. acnes biofilm structures. None of the fractions at 1000 μg/mL significantly modified the cytotoxic potential of S. epidermidis and S. aureus towards keratinocytes. However, poly- and oligosaccharide fractions at 1000 μg/mL induced a decrease in the inflammatory potential of both acneic and non-acneic C. acnes strains on keratinocytes of up to 39.8%; the strongest and most significant effect occurred when the bacteria were grown in the presence of polysaccharide fractions. Our research shows that poly- and oligosaccharide Ulva sp. fractions present notable biological activities on cutaneous bacteria, especially towards C. acnes acneic and non-acneic strains, which supports their potential use for dermo-cosmetic applications. 相似文献
90.
Nathalie Pinto Mathilde Neel Armen Panossian Dr. Pascal Retailleau Dr. Gilles Frison Dr. Arnaud Voituriez Dr. Angela Marinetti Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):1033-1045
The planar chiral 2‐phospha[3]ferrocenophane I has been shown to be the first efficient nucleophilic organocatalyst for the enantioselective synthesis of cyclopentenylphosphonates, through [3+2] cyclizations between diethyl allenylphosphonate and α,β‐unsaturated ketones. The same catalyst has also been applied to the highly enantioselective [3+2] cyclizations of allenic esters with dibenzylideneacetone and analogous bis‐enones, leading to functionalised cyclopentenes with either monocyclic or spirocyclic structures (ee 84–95 %). It has been shown that the residual enone functions in the resulting cyclopentenes can be involved in subsequent cyclization steps to afford unprecedented C2‐symmetric bis‐cyclopentenylketones. In order to provide insight into the behaviour of FerroPHANE I as a chiral catalyst in [3+2] cyclisations, the energetically most favoured isomers of the key phosphine‐allene adduct have been calculated by DFT methods. Factors likely to control the chiral induction process are highlighted. 相似文献