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Five unique compounds: xyloketals from mangrove fungus Xylaria sp. from the South China Sea coast 总被引:21,自引:0,他引:21
Lin Y Wu X Feng S Jiang G Luo J Zhou S Vrijmoed LL Jones EB Krohn K Steingröver K Zsila F 《The Journal of organic chemistry》2001,66(19):6252-6256
Five unique metabolites, xyloketals A (1), B (2), C (3), D (4), and E (5), and the known 6 were isolated from mangrove fungus Xylaria sp. (no. 2508), obtained from the South China Sea. The structures of these compounds were elucidated by spectroscopic and X-ray diffraction experiments. Xyloketal A is a ketal compound with a C(3) symmetry and xyloketals B-E are its analogues. It was found that xytoketal C slowly rearranged to xytoketal B in DMSO-d(6)() solution at room temperature. Xyloketal A exhibited the activity of inhibiting acetylcholine esterase. 相似文献
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A measurement of [GA/GV] in the decay of polarized neutrons, basically quite similar to our 1968 one, gives a value of 1.258±0.015. The asymmetry coefficient, A, is ?0.113±0.006. These results include the 1968 data. 相似文献
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Chris W. Patterson Robin S. McDowell Norris G. Nereson Richard F. Begley Harold W. Galbraith Burton J. Krohn 《Journal of Molecular Spectroscopy》1980,80(1):71-85
From a high-resolution diode laser spectrum of cooled 12CF4, line assignments in ν2 + ν4 at 1066.4 cm?1 have been made for tetrahedral subspecies to J = 20, and in many cases to higher J. Spectroscopic constants have been obtained from a least-squares fit of the Hamiltonian, and the relative intensities of the assigned lines have been calculated. The ground- and excited-state rotational constants, Coriolis constant, and splitting of the F1 and F2 vibrational substates have the values a.The CF bond length in the ground vibrational state is thus . The analysis of a combination band such as this provides a method of obtaining ground-state spectroscopic constants of spherical-top molecules directly from the infrared spectrum, without the necessity of measuring weak “forbidden” transitions. The assignments allow accurate predictions of the frequencies emitted by the CO2-pumped CF4 laser. 相似文献
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Burton J. Krohn 《Journal of Molecular Spectroscopy》1978,73(3):462-474
In the diode laser spectra of several P- and R-branches of high-J manifolds in the ν3 band of SF6 it has been observed that the lines are shifted away from the positions predicted by the diagonal FA1pp(4,R,R) approximation of Moret-Bailly. The shifts form a smooth function of the line positions across each manifold; this function can be represented empirically by a parabola, to which the measured wavenumbers fit within experimental accuracy. This phenomenon is explained here by model calculations for P-, Q-, and R-branch excited state levels that perturb each other through higher-order vibration-rotation interactions. In the analysis, eigenvalues calculated by second-order perturbation theory are compared with those obtained by diagonalization of the Hamiltonian. 相似文献
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