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971.
972.
973.
In this paper, we show that two Toeplitz operators Tf and Tg on the Hardy space of the polydisk can commute if and only if the Berezin transform of the commutator [Tf, Tg] is n-harmonic. 相似文献
974.
975.
Jia Sun Peicheng Zhang Qi Wei Hang Xun Feng Tang Yongde Yue Li Li Xuefeng Guo Rong Zhang 《Tetrahedron letters》2014
Amarusine A (1), a new polyketide derivative possessing an unusual dioxaspiro[4.4]nonane derivative with a butyrolactone ring, was isolated from the leaves of Pleioblastus amarus. The structure and absolute stereochemistry of compound 1 were rigorously determined using UV, IR, HRESIMS, and 1D and 2D NMR techniques and by comparing experimental and calculated electronic circular dichroism (ECD) spectra. Amarusine A (1) exhibits a good antioxidant activity for scavenging the DPPH radical. A possible biosynthetic pathway was postulated. 相似文献
976.
Yifan Dong Weilun Wang Cewen Zhong Jianbing Shi Bin Tong Xiao Feng Junge Zhi Yuping Dong 《Tetrahedron letters》2014
The emissive properties of fluorophores in aggregated state are important for the development of bio-sensors or bio-imaging reagents. So three water-soluble TPE derivatives with different lengths of side chains have been synthesized and we investigated the effects of side chains on aggregation-induced emission (AIE) properties in the aggregated states. The results indicate that side chains on the fluorophores play a pivotal role in their emission in aggregated state mediated by heparin or solid state, because the coplanarity of these TPE derivatives was affected by side chains. The rates of radiative decay kf and non-radiative decay knr have been obtained through the quantum yields and lifetime, and a larger kf and smaller knr were present for compound TPE-C4N, suggesting that the aggregated TPE-C4N should posses the most remarkable fluorescent property. 相似文献
977.
Dong-Bao Hu Wen-Xin Li Zhen-Zhu Zhao Tao Feng Rong-Hua Yin Zheng-Hui Li Ji-Kai Liu Hua-Jie Zhu 《Tetrahedron letters》2014
Four new highly unsaturated pyranone derivatives A–D (1–4), together with one known compound 5 (−)-nitidon were isolated from cultures of the fungus Junghuhnianitida. Planar structures of the new compounds were elucidated on the basis of extensive NMR spectroscopic and mass spectrometric analyses. Absolute configurations of the new compounds were determined on the basis of biosynthetic considerations and quantum chemistry theory. Compound 1 exhibited almost the same cytotoxic activities as cis-platin. 相似文献
978.
Abstract. Two new coordination polymers {[Cd2(BDC)2(3‐bpmp)(H2O)2] · 2H2O}n ( 1 ) and [Cd2(BDC)2(4‐bpmp)]n ( 2 ) [H2BDC = 5‐hydroxy‐isophthalic acid, 3‐bpmp = 1,4‐bis(3‐pyridylmethy)piperazine, and 4‐bpmp = 1,4‐bis(4‐pyridylmethy) piperazine] were synthesized via hydrothermal synthesis, and further characterized by IR spectroscopy, elemental analysis, XRD, and X‐ray crystallography. Complex 1 shows a two‐dimensional (4,4) sql topology and complex 2 features an 8‐connected hex topology. Moreover, the luminescent properties of complexes 1 and 2 were investigated in the solid state at room temperature. 相似文献
979.
Dian‐Feng Chen Feng Zhao Yue Hu Liu‐Zhu Gong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(40):10939-10943
A combination of either ruthenium(II) or rhodium(II) complexes and quinine‐derived squaramide enables 3‐diazooxindoles, indoles, and nitroalkenes to undergo highly efficient asymmetric three‐component reactions, thus affording optically active 3,3′‐bis(indole)s through a consecutive C C bond‐forming sequence, which turned out to be applicable to the facile total synthesis of (−)‐folicanthine. 相似文献
980.
Fengyan Wang Zhang Liu Bing Wang Liheng Feng Libing Liu Fengting Lv Yilin Wang Shu Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(2):434-438
The development of biomolecular fiber materials with imaging ability has become more and more useful for biological applications. In this work, cationic conjugated polymers (CCPs) were used to construct inherent fluorescent microfibers with natural biological macromolecules (DNA and histone proteins) through the interfacial polyelectrolyte complexation (IPC) procedure. Isothermal titration microcalorimetry results show that the driving forces for fiber formation are electrostatic and hydrophobic interactions, as well as the release of counterions and bound water molecules. Color‐encoded IPC fibers were also obtained based on the co‐assembly of DNA, histone proteins, and blue‐, green‐, or red‐ (RGB‐) emissive CCPs by tuning the fluorescence resonance energy‐transfer among the CCPs at a single excitation wavelength. The fibers could encapsulate GFP‐coded Escherichia coli BL21, and the expression of GFP proteins was successfully regulated by the external environment of the fibers. These multi‐colored fibers show a great potential in biomedical applications, such as biosensor, delivery, and release of biological molecules and tissue engineering. 相似文献