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101.
Nguyen Xuan Nhiem Hwa Young Lee Nan Young Kim Seon Ju Park Eun Sil Kim Jeong Eun Han Heejung Yang Seung Hyun Kim 《Magnetic resonance in chemistry : MRC》2012,50(11):772-777
The chemical study of the leaves and twigs of Viscum album led to the isolation of five new lignan glycosides, namely, ligalbumosides A–E (2‐6) and one known lignan glycoside, alangilignoside C (1). The structures of five new lignan glycosides were determined to be (7R,8S,8'S)‐4,9,4'‐trihydroxy‐3,5,3',5'‐tetramethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (2), (7S,8S,7'S,8'R)‐4,9,4'‐trihydroxy‐3,5,3',5',7'‐pentamethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (3), (7R,8R,7'S,8'S)‐4,9,4'‐trihydroxy‐3,5,3',5',7'‐pentamethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (4), (7S,8R,7'S,8'R)‐4,9,4'‐trihydroxy‐3,5,3',5',7'‐pentamethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (5), and (7R,8S,7'R,8'S)‐4,9,4',7'‐tetrahydroxy‐3,5,3',5'‐tetramethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (6) using 1D‐, 2D‐NMR, and CD spectra, chemical methods, as well as comparing the results with those reported in the literature. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
102.
103.
We discuss the value of the best constant in Gaffney inequality namely when either or on ?Ω. 相似文献
104.
Protein tyrosine phosphatase 1beta (PTP1beta) acts as a negative regulator of insulin signaling. Selective inhibition of PTP1beta has served as a potential drug target for the treatment of type 2 diabetes mellitus. We evaluated the inhibitory effect of Phellinus linteus against PTP1beta as part of our ongoing search for natural therapeutic and preventive agents for diabetes mellitus. Fractions of the P. linteus extract were found to exhibit significant inhibitory activities against PTP1beta. In an attempt to identify bioactive components, we isolated, from the most active ethyl acetate fraction, five hispidin derivatives (phelligridimer A, davallialactone, hypholomine B, interfungins A, and inoscavin A) and four phenolic compounds (protocatechuic acid, protocatechualdehyde, caffeic acid, and ellagic acid). The chemical structures of these compounds were elucidated from spectroscopic evidence and by comparison with published data. All the compounds strongly inhibited PTP1beta activity in an in vitro assay; their IC50 values ranged from 9.0 +/- 0.01 to 58.2 +/- 0.3 microM. Our results indicated that the hispidin skeleton may be an important moiety for inhibitory activity of the above compounds against PTP1beta. Thus, hispidin derivatives could be a potent new class of natural PTP1beta inhibitors. 相似文献
105.
Yeon Sil Park 《Tetrahedron letters》2010,51(30):3956-3959
Tetrapyridinohemicarcerand 2 having four hydrogen-bonding acceptors of inward-directing pyridyl units was synthesized and their binding properties for a variety of organic guest molecules have been investigated. Tetrapyridinohemicarcerand 2 formed kinetically stable complexes with various sulfonic acids via intermolecular -SO3H-pyridyl hydrogen bonding and constrictive binding interactions in C2D2Cl4 at 25 °C. But carboxylic acids or alcohols cannot be a stable guest at the same conditions. Tetrapyridinohemicarcerand 2 also binds various disubstituted benzenes. Especially 1,4-diiodobenzene forms stable hemicarceplex 1,4-diiodobenzene@2, which seems to be stabilized by constrictive binding as well as by -C-H?I interactions between dioxymethylene of 2 and iodo group of guest. 相似文献
106.
[reaction: see text] A novel C3V-symmetric scaffold, trindane 7, has been efficiently synthesized from 1,3,5-tris(bromomethyl)-2,4,6-tris(chloromethyl)benzene (1) in six steps with 47% overall yield. The control of all-syn stereochemistry in the tribenzylation step has been achieved by blocking one side of the trindane ring as metal carbonyl complexes. The potential utility of trindane 7 as a receptor skeleton has been examined with a urea derivative 12 toward several anionic guests. 相似文献
107.
The scattering of positrons by atoms and molecules is reviewed. The recent development of monoenergetic slow positron beams and their applications to the measurement of cross sections for positrons interacting in various gases are discussed briefly. The theoretical development of positron collisions in gases is covered from the beginning. Both elastic and the inelastic processes have been included. Comparisons are made between the measured values and theoretical predictions. The deficiencies of the theoretical models and experimental apparatus are also pointed out. 相似文献
108.
A separable representation for the off-shell two-body t-matrix for a local Hulthén potential is presented, in which deuteron states are chosen as the expansion bases. Using the Faddeev equations with these t-matrices as input, the ground state energy of the triton and doublet and quartet scattering lengths in neutron-deuteron scattering, have been computed. The results have been compared with the experimental findings and the theoretical results of Sitenko et al. obtained in the Sturmian function representation with the same Hulthén potential. 相似文献
109.
Johan V. Silén 《Physics letters. A》1979,70(3):202-204
By considering the boundary of a jet as a discontinuity, the ratio of the boundary shock velocity and the axial flow velocity may be regarded as the spatial derivative of the boundary curve. The obtained equation can be solved asymptotically. 相似文献
110.
A unified approach in the light of supersymmetric quantum mechanics (SSQM) has been suggested for generating multidimensional
quasi-exactly solvable (QES) potentials. This method provides a convenient means to construct isospectral potentials of derived
potentials.
相似文献