排序方式: 共有49条查询结果,搜索用时 15 毫秒
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Sequential ring-closing metathesis (RCM)-Kharasch cyclizations are promoted by the Grubbs metathesis catalysts and provide rapid access to bicyclic lactones and lactams. 相似文献
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Stephen A. Eastham Michael R. Hallett Andrea Modi James E. Painter Peter Quayle Dean C. Ricketts 《Tetrahedron》2008,64(5):936-948
The development of a formal synthesis of aflatoxin B2 is described, which utilizes a Dötz benzannulation reaction as a key step. 相似文献
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Asai S. Azuelos G. Buttar C. Cavasinni V. Costanzo D. Cranmer K. Harper R. Jakobs K. Kanzaki J. Klute M. Mazini R. Mellado B. Quayle W. Richter-Ws E. Takemoto T. Vivarelli I. Wu Sau Lan 《The European Physical Journal C - Particles and Fields》2003,32(2):s19-s54
The European Physical Journal C - The potential for the discovery of a Standard Model Higgs boson in the mass range m H < 2 m Z in the vector boson fusion mode has been studied for the ATLAS... 相似文献
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AR Engel 《Contemporary Physics》2013,54(6):523-526
This article reviews some of the applications of physics to the solution of archaeological problems. The use of magnetic, resistivity and electromagnetic surveying techniques for the location of buried features is described. Various methods of age determination are outlined while the problems associated with radiocarbon dating of organic material and thermoluminescent dating of pottery are discussed in detail. The techniques, including petrological examination, chemical analysis and isotopic analysis, employed in the physical examination of archaeological artefacts are described. Examples of the application of these techniques in establishing the source of the raw materials used in pottery, metal and stone implements and in elucidating the techniques of manufacture of pottery and metal objects are also given. 相似文献
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In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•+), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•+, DPPH•, and FRAP activities (IC50: 0.05 ± 0.0001 mg/mL, IC50: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC50: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source. 相似文献
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Michael R. Attwood Mark L. Lewis Peter Quayle Simon P. Thompson 《Tetrahedron letters》2006,47(21):3607-3611
α-Alkoxystannanes undergo oxidation upon treatment with cerium ammonium nitrate generating oxonium ions, which can be trapped in an intramolecular fashion affording furo[2,3-b]pyrans. 相似文献