排序方式: 共有19条查询结果,搜索用时 31 毫秒
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The synthesis of 5- to 8-memebered cyclic thioethers 4 has been achieved through a simple two-step sequence. The present methodology utilizes the facile Friedel-Crafts acylation of terminal alkynes 1 with acid chlorides 2 followed by tandem C(sp(3))-S and C(sp(2))-S bond formations with NaSH.xH(2)O. 相似文献
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Scott WL Martynow JG Huffman JC O'Donnell MJ 《Journal of the American Chemical Society》2007,129(22):7077-7088
A wide variety of highly substituted lactam containing peptidomimetic scaffolds are prepared by solid-phase synthesis from a single, versatile class of resin-bound aldehyde intermediates (1). These include monocyclics 3, bicyclics 4, tricyclics 5, and tetracyclics 6. The key intermediate 1 is readily synthesized from resin-bound natural or unnatural alpha-amino acids. The synthetic procedures permit the construction of a large diversity of substitution patterns for ready use in combinatorial chemistry. In every case, the release of final products from resin is by a cyclitive cleavage process. Since this depends on successful completion of multiple intermediate synthetic steps, the products are often quite pure, even though previous steps involve only a filtration workup. The mild conditions for many of these synthetic procedures offer the promise of using this chemistry in peptide fragment condensations to produce modified peptides, at either the N-terminus or C-terminus, or as individually assembled peptide segments with a wide variety of conformationally restricted peptidomimetic linkers at the point of juncture. 相似文献
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The stereospecific synthesis of 3β-acetoxycholest-5-en-7β-ol from cholesterol is described. 相似文献
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B Salimbahrami B Lohmann T Bechtold JG Korvink 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(1):79-93
In this paper we introduce a two-sided Arnoldi method for the reduction of high order linear systems and we propose useful extensions, first of all a stopping criterion to find a suitable order for the reduced model and secondly, a selection procedure to significantly improve the performance in the multi-input multi-output (MIMO) case. One application is in micro-electro-mechanical systems (MEMS). We consider a thermo-electric micro thruster model, and a comparison between the commonly used Arnoldi algorithm and the two-sided Arnoldi is performed. 相似文献
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Miłosz Martynow Dr. Damian Głowienka Dr. Jędrzej Szmytkowski Dr. Yulia Galagan Dr. Julien Guthmuller 《Chemphyschem》2019,20(23):3228-3237
An experimental and theoretical investigation is reported to analyze the relation between the structural and absorption properties of CH3NH3PbI3 in the tetragonal phase. More than 3000 geometry optimizations were performed to reveal the structural disorder and identify structures with the lowest energies. The electronic structure calculations provide an averaged band gap of 1.674 eV, which is in excellent agreement with the experimental value of about 1.6 eV. The simulations of the absorption spectrum for three representative structures with lowest energy reproduced the absorption shoulders observed in the experimental spectra. These shoulders are assigned to excitations having similar orbital characters and involving transitions between hybridized 6s(Pb)/5p(I) orbitals and 6p(Pb) orbitals. The geometries of the three structures were analyzed and the effects of the inorganic frame and the CH3NH3+ cations on the absorption properties were estimated. It was found that both changes in the inorganic frame and the CH3NH3+ cations orientations impact the absorption spectra, by modifying the transitions energies and intensities. This highlights the role of CH3NH3+ cation in influencing the absorption properties of CH3NH3PbI3 and demonstrates that CH3NH3+ cation is one of the key elements explaining the broad and nearly constant absorption spectrum in the visible range. 相似文献
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Munshi G Mustafa Sudhir Raniwala T Awes B Rai RS Bhalerao JG Contreras RV Gavai SK Ghosh P Jaikumar GC Mishra AP Mishra H Mishra B Mohanty J Nayak J-Y Ollitrault SC Phatak L Ramello R Ray PK Sahu AM Srivastava DK Srivastava VK Tiwari 《Pramana》2006,67(5):961-981
This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and
work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported. 相似文献