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101.
Kuzma M Jegorov A Hesso A Tornaeus J Sedmera P Havlícek V 《Journal of mass spectrometry : JMS》2002,37(3):292-298
The product ion mass spectra (collisionally induced dissociation mass spectra) of 12 different cyclosporins modified at every N-methylated amino acid residue with respect to cyclosporin A were compared and the effect of N-demethylation on ring opening mechanisms was evaluated. The four preferential protonation sites were identified in [MeBmt(1)]-cyclosporins. Three sites represented the N-methylated nitrogens of Sar(3), MeLeu(6) and MeLeu(9), while the remaining one represented the lactone group formed by the intramolecular N,O-acyl shift. Selective N-demethylation resulted either in the deletion of the entire fragment ion series or its substantial attenuation. The structures of three new natural cyclosporins in the study were supported by NMR data. 相似文献
102.
103.
Albina Y. Ziganshina Sergey V. Kharlamov Dmitry E. Korshin Rezeda K. Mukhitova Ella Kh. Kazakova Shamil K. Latypov Vitaly V. Yanilkin Alexandr I. Konovalov 《Tetrahedron letters》2008,49(36):5312-5315
A new molecular capsule based on viologen-resorcinarene and sulfonatomethylene-resorcinarene is synthesized and its redox-controlled stability is investigated. 相似文献
104.
Ekaterina V. Shevaldina Ksenia A. Opredelennova Olga A. Chichvarina Yury Ya. Spiridonov Alexandr F. Smol'yakov Pavel V. Dorovatovskii Sergey K. Moiseev 《应用有机金属化学》2019,33(11)
α‐Ferrocenylalkylation of azoles or S‐nucleophiles with FcCH(R)OH (Fc = ferrocenyl) can be accomplished under acid‐free conditions as one‐pot process via an intermediate formation of the α‐ferrocenylalkyl carbonates FcCH(R)OC(O)OEt. The reaction allows the alkylation of acid sensitive substrates like imidazole derivatives or sodium N,N‐diethyldithiocarbamate. The reaction with ambident azoles proceeds as the N‐alkylation. Some α‐ferrocenylalkyl azoles were found to exhibit plant growth stimulating or herbicidal effects on corn seeds or act as the herbicide safeners against sulfonylurea herbicides. 相似文献
105.
Dr. Jinhua Sun Artem Iakunkov Dr. Igor A. Baburin Boby Joseph Prof. Vincenzo Palermo Dr. Alexandr V. Talyzin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1103-1108
COF-1 has a structure with rigid 2D layers composed of benzene and B3O3 rings and weak van der Waals bonding between the layers. The as-synthesized COF-1 structure contains pores occupied by solvent molecules. A high surface area empty-pore structure is obtained after vacuum annealing. High-pressure XRD and Raman experiments with mesitylene-filled (COF-1-M) and empty-pore COF-1 demonstrate partial amorphization and collapse of the framework structure above 12–15 GPa. The ambient pressure structure of COF-1-M can be reversibly recovered after compression up to 10–15 GPa. Remarkable stability of highly porous COF-1 structure at pressures at least up to 10 GPa is found even for the empty-pore structure. The bulk modulus of the COF-1 structure (11.2(5) GPa) and linear incompressibilities (k[100]=111(5) GPa, k[001]=15.0(5) GPa) were evaluated from the analysis of XRD data and cross-checked against first-principles calculations. 相似文献
106.
We present a generalization of the concept of semiholonomic jets within the framework of higher order prolongations of a fibred manifold. In this respect, a compilation of our 2-fibred manifold approach with the methods of natural operators theory is used. 相似文献
107.
108.
Water‐Soluble Gold Nanoparticles: From Catalytic Selective Nitroarene Reduction in Water to Refractive Index Sensing 下载免费PDF全文
Water‐soluble gold nanoparticles (Au NPs) stabilized by a nitrogen‐rich poly(ethylene glycol) (PEG)‐tagged substrate have been prepared by reduction of HAuCl4 with NaBH4 in water at room temperature. The morphology and size of the nanoparticles can be controlled by simply varying the gold/stabilizer ratio. The nanoparticles have been fully characterized by TEM, high‐resolution (HR) TEM, electron diffraction (ED), energy‐dispersive X‐ray spectroscopy (EDS), UV/Vis, powder XRD, and elemental analysis. The material is efficient as a recyclable catalyst for the selective reduction of nitroarenes with NaBH4 to yield the corresponding anilines in water at room temperature. Furthermore, the potential ability of the Au NPs as a refractive index sensor owing to their localized surface plasmon resonance (LSPR) effect has also been assessed. 相似文献
109.
Sergey Avgustinovich Sergey Kitaev Alexandr Valyuzhenich 《Discrete Applied Mathematics》2013,161(1-2):43-51
We introduce the notion of a boxed mesh pattern and study avoidance of these patterns on permutations. We prove that the celebrated former Stanley–Wilf conjecture is not true for all but eleven boxed mesh patterns; for seven out of the eleven patterns the former conjecture is true, while we do not know the answer for the remaining four (length-four) patterns. Moreover, we prove that an analogue of a well-known theorem of Erd?s and Szekeres does not hold for boxed mesh patterns of lengths larger than 2. Finally, we discuss enumeration of permutations avoiding simultaneously two or more length-three boxed mesh patterns, where we meet generalized Catalan numbers. 相似文献
110.
V. A. Voitovich 《Polymer Science Series D》2009,2(4):261-264
The influence of ethylsilicate additive on the properties of epoxide compositions and cured films on their basis was investigated.
It was shown that the introduction of ES-32 ethylsilicate to epoxide composition formulation reduces their viscosity and favors
the significant improvement of the physicomechanical properties of cured polymers. 相似文献