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991.
Phytochemical studies of the leaves and rhizomes of Paraboea pa niculata (Gesneriaceae) are reported for the first time. Three phenylethanoid glycosides were isolated and characterized as 3,4-dihydroxyphenethyl-(3"-O-beta-D-apiofuranosyl)-beta-D-glucopyranoside, calceoralarioside E, and acteoside. These isolates exhibited weak cytotoxic activity against the K-562 cell line with a 50% of cell killing rate of 40.18 microM, 27.05 microM, and 27.24 microM, respectively. In the DPPH free radical scavenging assay, their IC50 values were determined as 75.89 microM, 25.00 microM, and 26.04 microM, respectively. 相似文献
992.
993.
Ye F Wu C Jin Y Wang M Chan YH Yu J Sun W Hayden S Chiu DT 《Chemical communications (Cambridge, England)》2012,48(12):1778-1780
We demonstrate a new compact CN-PPV dot, which emits in the orange wavelength range with high brightness. The small particle size, high brightness, and the ability to highly specifically target subcellular structures make the CN-PPV dots promising probes for biological imaging and bioanalytical applications. 相似文献
994.
Chao WS Liao KH Chen CT Huang WK Lan CM Diau EW 《Chemical communications (Cambridge, England)》2012,48(40):4884-4886
Hybrids based on a dibenzosuberene core bearing a spiro-fluorene junction at the C-5 position and with amino donor and β-thiophenyl-α-cyanoacrylic acid acceptor groups at C-3 and C-7, respectively, serve as new organic sensitizer materials for solar cell applications. Solar cell devices based on these materials show a conversion efficiency (η) of up to 6.1% (V(oc) = 697 mV, J(sc) = 12.2 mA cm(-2), FF = 0.72) under AM 1.5 G conditions. The best IPCE values exceed 75% within the 450-550 nm absorption range. 相似文献
995.
Yubo ChenDengjie Chen Ran RanHee Jung Park Chan KwakSung Jin Ahn Kyeong Suk MoonZongping Shao 《Electrochemistry communications》2012,14(1):36-38
Nickel oxide was introduced as a grain growth inhibitor into Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF) electrode to increase its activity for oxygen reduction reaction. Small amount of NiO can effectively suppress the grain growth of BSCF by spinning the grain boundary and thus increase the electrode surface area, while the particle connection is not obviously affected. Electrochemical impedance spectra of symmetric cells indicate that the electrode activity for oxygen reduction is indeed effectively improved by introducing NiO additive. At 600 °C, area specific resistance of BSCF+5wt.% NiO is about 36.5% lower than that of pure BSCF electrode. Single cell tests also demonstrate an improved cell power output by introducing NiO additive. It implies that the adoption of a sintering inhibitor may be a facile and practical way to increase electrode activity for oxygen reduction. 相似文献
996.
So LC Liu CC Chan MC Lo JC Sze KH Zhu N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(2):565-573
The nature and importance of C-H···F-C interactions is a topical yet controversial issue, and the development of spectroscopic methods to probe such contacts is therefore warranted. A series of Group 4 bis(benzyl) complexes supported by (σ-aryl)-2-phenolate-6-pyridyl [O,C,N-R(1)] ligands bearing a fluorinated R(1) group (CF(3) or F) in the vicinity of the metal has been prepared. The X-ray crystal structure of the CF(3)-substituted Hf derivative features intramolecular C-H···F-C and Hf···F-C contacts. All complexes have been characterized by multinuclear NMR spectroscopy. The (1)H and (13)C NMR spectra of [M(O,C,N-CF(3))(CH(2)Ph)(2)] derivatives display coupling (assigned to (1h)J(HF) and (2h)J(CF) for Ti; (3)J(HF) and (2)J(CF) (through M···F) for Hf and Zr) between the benzyl CH(2) and CF(3) moieties. [(1)H,(19)F]-HMBC NMR experiments have been performed for the M-[O,C,N-R(1)] complexes and their [O,N,C] counterparts, revealing significant scalar coupling across the C-H···F-C interactions for Ti-[O,C,N] and [O,N,C] species. 相似文献
997.
998.
C.H. WangS.N. Schwartz S. AlluriT.M. Cattabiani L.K. ZhangT.M. Chan A.V. BuevichA.K. Ganguly 《Tetrahedron》2012,68(47):9750-9762
This paper describes a novel synthetic route for the preparation of ortho-ortho disubstituted biphenyls and compounds possessing highly condensed ring system represented by structures X and Y, respectively. Several approaches, such as intermolecular Grubb's olefin metathesis, Heck and, Suzuki reactions were incorporated to functionalize the core structures of X and Y making it suitable for the preparation of a library of compounds. 相似文献
999.
A new synthetic route for binaphthyl-based secondary amines has been developed. The key features of this route include the selective direct esterification of the binaphthyl structure at the 3- or 3,3'-position and the methylation by a Negishi cross-coupling reaction. Based on the new approach, a series of 3-monosubstituted and 3,3'-disubstituted chiral secondary amines with a binaphthyl backbone were synthesized and screened in the Michael reaction of aldehydes to various nitroalkenes. 3-Monosubstituted secondary amine 7c was proved to be the best catalyst, affording high yields (up to 95%), good to excellent enantioselectivities (up to 99%) and diastereoselectivities (syn/anti up to 99:1) under the optimized conditions. 相似文献
1000.
We prove two identities related to overpartition pairs. One of them gives a generalization of an identity due to Lovejoy, which was used in a joint work by Bringmann and Lovejoy to derive congruences for overpartition pairs. We apply our two identities on pairs of partitions where each partition has no repeated odd parts. We also present three partition statistics that give combinatorial explanations to a congruence modulo 3 satisfied by these partition pairs. 相似文献