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41.
Starting from shikimic acid, the total synthesis of zeylenone was studied. The product was proved to be the (+)antipode of zeylenone through analysis and comparison of their respective spectra (including NMR, MS, IR and CD) and optical data. The absolute configuration of the natural product was thus determined to be (1S,2S,3R). 相似文献
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Arata Yajima 《Tetrahedron》2005,61(38):9164-9172
A versatile methodology for the synthesis of various terpenoids via B-alkyl Suzuki-Miyaura coupling as a key step is established. Synthesis of cordiaquinone J and K, new antifungal and larvicidal meroterpenoids, was achieved by using this methodology. The absolute configurations of cordiaquinone J and K were confirmed by the synthesis. 相似文献
44.
The recently proposed electron-hole potential (EHP) method for excited states is extended to the multi-configurational case. The variation equation is solved using the quadratic convergence method. The EHP methods are shown to be approximations to the complete singly excited configuration interaction (CSECI) in the variational sense. Extended Brillouin theorems are proved for the EHP methods. The excitation energies and wave functions obtained by one and two configurational EHP methods agree well with those of the CSECI method. The EHP methods have clear advantage in the computer time requirement over the CI method and are especially suited for a calculation of approximate excited states of large molecules. The EHP methods are applicable to excited states which belong to the same irreducible representation as the ground state. 相似文献
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The title Schiff base compound,C19H19N3O3,a derivative of antipyrine,has been synthesized and characterized by elemental analysis,IR,and single-crystal X-ray diffraction.The crystal belongs to the monoclinic system,space group C2/c,with α = 27.935(5),b = 7.553(1),c =16.692(3) (A),β = 105.810(3)°,Z= 8,V= 3388.7(10) (A)3,Dc = 1.323 g/cm3,Mr = 337.37,λ(MoKα) =0.71073 (A),μ = 0.091 mm-1,F(000) = 1424,R = 0.0630 and wR = 0.1273.A total of 3513 unique reflections were collected,of which 2112 with I > 2σ(I) were observed.The molecular structure adopts a trans configuration about the C=N double bond.The pyrazoline and C(1)~C(6) pheny1 ring are approximately coplanar (mean deviation from the combined plane is 0.069(3) (A)),with the dihedral angle of 9.7(2)°.The preliminary biological tests show that the compound has high antibacterial activities. 相似文献
48.
Lophenol, cholest-4α-methyl-7-en-3β-ol (1), obtained from Dracaena cochinchinensis (Lour.) S. C. Chen, was structurally modified. It was acetylated to protect 3β-hydroxyl group, and then oxidised by selenium dioxide in acetic acid to give cholest-4a-methyl-8-en-3β, Ta-diol diacetate (3). This compound 3 is unstable in chloroform solution or when heated and easily converted to a diene compound, cholest-4a-methyl-7,14-dien-3β-ol acetate (4). The structures of 3 and 4 were elucidated by means of IR, ^1H NMR, ^13C NMR and MS, and the absolute configuration of 3 was established by X-ray crystallography. The property of 3 was also discussed in this paper. Both 3 and 4 are new compounds and were reported for the first time. 相似文献
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Chemical Bonding and Pressure‐Induced Change of the Electron Configuration of Ytterbium in β‐YbAgGa2
Ulrich Schwarz Marcus Schmidt Roman Gumeniuk Walter Schnelle Michael Hanfland Konstantin Klementiev Yuri Grin 《无机化学与普通化学杂志》2004,630(1):122-126
Single‐phase polycrystalline samples of the intermetallic compound β‐YbAgGa2 were synthesized by inductive heating and subsequent annealing for eight weeks at 670 K. Magnetic properties were characterized by susceptibility measurements and indicated intermediate valence of ytterbium at ambient pressure. Angle‐dispersive X‐ray powder diffraction data of orthorhombic β‐YbAgGa2 indicate stability of the phase in the investigated pressure range from 0.1 MPa (ambient pressure) to 19 GPa. The pressure‐induced volume decrease is accompanied by an increase of the effective valence from 2.17 at ambient conditions to 2.71 at 16 GPa as evaluated by X‐ray absorption spectroscopy at the Yb LIII threshold. Analysis of the chemical bonding in β‐YbAgGa2 by integrating the electron density of the polyanion in basins as defined by the electron localization function results in an electron count Yb2.7+[(Ag0.2—)(Ga1(3b)1.0—)(Ga2(4b)1.5—)]. This finding is close to the expected values calculated by means of the Zintl rules and fits well the results of magnetic susceptibility measurements and XAS investigations. 相似文献