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1.
Xu‐Wen Li Alexandre Ear Lukas Roger Dr. Nassima Riache Alexandre Deville Dr. Bastien Nay 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16389-16393
A bio‐inspired strategy was used to complete the formal synthesis of the antitubercular hirsutellone B and congeners A and C, through construction of its decahydrofluorene core from a linear polyene strand activated at both ends by a silyl enol ether and an allyl acetate. Our synthesis features a key electrophilic cyclization, starting with the remote activation (by [Yb(OTf)3] or BF3 ? OEt2) of the allyl acetate and stereoselectively affording the C ring. This was followed by an intramolecular Diels–Alder reaction to get the tricyclic core of the natural product. The stereoselective reduction of the resulting ketone towards the formal intermediate was critical to the success of this strategy. 相似文献
2.
B. Vincent R. Kremer A. Boudrioua P. Moretti Y.-C. Zhang C.-C. Hsu L.-H. Peng 《Applied physics. B, Lasers and optics》2007,89(2-3):235-239
An optical planar waveguide is investigated in ZnO-doped periodically poled lithium niobate formed by He+ implantation. Optical losses were found to be 2 dB/cm. Second-harmonic generation is used to produce a green laser beam by
quasi-phase matching in the obtained waveguide. The conversion efficiency was found to be 10-2%/W. Photorefractive resistance properties are reported and discussed relating to un-doped periodically poled lithium niobate.
PACS 42.65.-k; 42.65.Wi; 42.82.-m 相似文献
3.
Corrigendum: Cyclooctane Metathesis Catalyzed by Silica‐Supported Tungsten Pentamethyl [(SiO)W(Me)5]: Distribution of Macrocyclic Alkanes 下载免费PDF全文
4.
A planar waveguide composed of the new nonlinear material, Ca(4)GdO(BO(3))(3) (GdCOB), is reported. This crystal belongs to the calcium oxoborate family. It has attractive nonlinear properties that can be of great interest in integrated optics applications. We used a method of He(+) implantation to fabricate waveguides in GdCOB crystals by creating a buried layer of lowered refractive index a few micrometers beneath the surface. Both TE and TM modes were observed. Therefore, according to the Y cut of the crystal, refractive-index values of n(x) , n(y) , and n(z) were obtained. Index profiles were reconstructed by an improved inverse WKB method. The profiles showed a steplike index behavior, indicating that the guiding region obtained was of good optical quality. 相似文献
5.
Vincent B Boudrioua A Loulergue JC Moretti P Tascu S Jacquier B Aka G Vivien D 《Optics letters》2003,28(12):1025-1027
Blue light at 405 nm is generated by frequency doubling of a Ti:sapphire tunable laser in He(+)-implanted channel waveguides in gadolinium calcium oxoborate crystal. A conversion efficiency of approximately 2% W(-1) cm(-2) is achieved between TM00 fundamental and TE01 harmonic modes. 相似文献
6.
Benyoub Nassima Barça Abdelhafid Selâdji Fawzia Benhamou Abdellah Debab Abdelkader 《Research on Chemical Intermediates》2021,47(10):4311-4331
Research on Chemical Intermediates - The single and binary adsorption of two anionic dyes Acid Yellow 17 (AY17) and Naphtol Green B (NGB) onto N–N–Dimethyl-n-octylamine (DMOA) modified... 相似文献
7.
Zahia Houiene Mounia Merabet-Khelassi Nassima Bouzemi Olivier Riant Louisa Aribi-Zouioueche 《Tetrahedron: Asymmetry》2013,24(5-6):290-296
Herein we report results of the chemoenzymatic deracemization of a range of secondary benzylic acetates 1a–9a via a sequence of hydrolysis with CAL-B lipase in non-conventional media, combined with esterification of the recovered alcohol according to the Mitsunobu protocol following an enzymatic kinetic resolution (KR). The KR of racemic acetates 1a–9a via an enzymatic hydrolysis, with CAL-B lipase and Na2CO3, in non-aqueous media was optimized and gave high selectivities (E ? 200) at good conversions (C >49%) for all of the substrates studied. This method competes well with the traditional one performed in a phosphate buffer solution. The deracemization using Mitsunobu inversion gave the (S)-acetates in moderate to excellent enantiomeric excess 75% < ee < 99%, in acceptable isolated yields 70% < yield < 89%, and with some variations according to the acetate structure. 相似文献
8.
Electronic structure and spectroscopic properties of 6‐aminophenanthridine and its derivatives: Insights from density functional theory 下载免费PDF全文
Hakkim Vovusha Debapriya Banerjee Nassima Oumata Biplab Sanyal Suparna Sanyal 《International journal of quantum chemistry》2015,115(13):846-852
6‐Aminophenanthridine (6AP) and its derivatives show important biological activities as antiprion compounds and inhibitors of the protein folding activity of the ribosome. Both of these activities depend on the RNA binding property of these compounds, which has been recently characterized by fluorescence spectroscopy. Hence, fundamental insights into the photophysical properties of 6AP compounds are highly important to understand their biological activities. In this work, we have calculated electronic structures and optical properties of 6AP and its three derivatives 6AP8CF3, 6AP8Cl, and 6APi by density functional theory (DFT) and time‐dependent density functional theory (TDDFT). Our calculated spectra show a good agreement with the experimental absorption and fluorescence spectra, and thus, provide deep insights into the optical properties of the compounds. Furthermore, comparing the results obtained with four different hybrid functionals, we demonstrate that the accuracy of the functionals varies in the order B3LYP > PBE0 > M062X > M06HF. © 2015 Wiley Periodicals, Inc. 相似文献
9.
Mohamed Lazoul Azzedine Boudrioua Lotfy Mokhtar Simohamed Alexis Fischer Lung Han Peng 《Applied physics. B, Lasers and optics》2013,110(4):459-464
We report a detailed study of multiple wavelengths optical parametric generation in a single grating one-dimensional periodically poled lithium tantalate crystal. Simultaneous collinear and non-collinear generations are observed around the pump collinear direction. Similar spectra are found in continuous spatial positions symmetrical to the collinear direction, with decreasing signal and increasing idler wavelengths, associated with decreasing powers when the far-field angle increases. A phase matching scheme is proposed to describe these interactions. Numerical simulations emphasize the agreement of our phase matching scheme with the experimental results. Single-pass gain and high pump power density are very likely at the origin of the simultaneous collinear and non-collinear QPM interactions. 相似文献
10.
Nassima Boudrioua Azzedine Boudrioua Fabrice Monteiro Etienne Losson Abas Dandache Rgis Kremer 《Optics Communications》2008,281(19):4870-4875
We have studied the effect of temperature on the birefringence and polarization mode dispersion PMD in standard single mode fibre (SSMF) with elliptical core cross section by using numerical computations. On the basis of simulation we have concluded that PMD fluctuates more rapidly than the stress-induced birefringence. In addition, DGD is inversely proportional to temperature. 相似文献