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91.
Jaffe DE Straub PB Adams MR Brown CN Charpak G Cooper WE Crittenden JA Finley DA Glass HD Gray R Hemmi Y Hsiung YB Hubbard JR Jonckheere AM Jöstlein H Kaplan DM Lederman LM Luk KB Maki A Mangeot P McCarthy RL Miyake K Plaag RE Rutherfoord JP Sakai Y Santiard JC Sauli F Smith SR Yoshida T Young KK 《Physical review D: Particles and fields》1989,40(9):2777-2795
92.
93.
Sudo Y Shirasaki D Harada S Nishida A 《Journal of the American Chemical Society》2008,130(38):12588-12589
1-Methoxy-3-trimethylsiloxy-1,3-butadiene (Danishefsky's diene) is recognized as a synthetically useful diene due to its high reactivity in the Diels-Alder reaction with electron-deficient alkenes to give oxygen-functionalyzed cyclohexenes and substituted cyclohexenones, which are important building blocks for the total synthesis of natural products. However, the development of catalytic enantioselective versions of Diels-Alder reactions using Danishefsky type dienes with electron-deficient alkenes has been difficult because of the instability of the dienes under Lewis acidic conditions. Only highly reactive CO and CN double bonds are employed in a hetero-Diels-Alder reaction which proceeds under catalysis of chiral Lewis acids. We have developed a new chiral ligand, BINAMIDE, which is easily prepared from 1,1'-binaphtyl-2,2'-diamine by acylation. The highly diastereo- and enantioselective Diels-Alder reaction of Danishefsky type dienes with electron-deficient alkenes in the presence of an Yb(III)-BINAMIDE complex has been developed. The reaction proceeded in an exoselective mode and gave chiral highly functionalized cyclohexene derivatives in good yields. 相似文献
94.
[reaction: see text] The one-pot construction of polycyclic aromatic systems from acyclic ene-bis(propargyl alcohols) was achieved through a tandem dual [2,3]-sigmatropic rearrangement/6pi-electrocyclic reaction/intramolecular [4 + 2] cycloaddition sequence. A steroidal compound was conveniently synthesized using the present method. 相似文献
95.
The additive Pummerer reaction of several heteroaromatic sulfilimines has been investigated. The overall process involves the reaction of the sulfilimine with TFAA to produce a transient N-tosyl-N-trifluoroacetyl sulfonium ion. Nucleophilic attack at the adjacent vinyl carbon results in the ejection of the sulfonamide group and the resulting thionium ion loses a proton to give the observed product. 相似文献
96.
Soga S Shirai H Kobori M Hirayama N 《Journal of chemical information and modeling》2008,48(8):1679-1685
The idea that there should be a specific site on a protein for a particular functional small molecule is widespread. It is, however, usually not so easy to understand what characteristics of the site determine the binding ability of the functional small molecule. We have focused on the concurrence rate of the 20 standard amino acids at such binding sites. In order to correlate the concurrence rate and the specific binding site, we have analyzed high-quality X-ray structures of complexes between proteins and small molecules. A novel index characterizing the binding site based on the concurrency rate has been introduced. Using this index we have identified that there is a specific concavity designated as a chemocavity where a specific group of small molecules, i.e., canonical molecular group, is highly inclined to be bound. This study has demonstrated that a chemocavity is reserved for a specific canonical molecular group, and the prevalent idea has been confirmed. 相似文献
97.
A chemomechanical actuator utilizing a reaction-diffusion wave across gap junction was constructed toward a novel mircoconveyer by micropatterned self-oscillating gel array. Unidirectional propagation of the chemical wave of the Belousov-Zhabotinsky (BZ) reaction was induced on gel arrays. In the case of using a triangle-shaped gel as an element of the array, the chemical wave propagated from the corner side of the triangle gel to the plane side of the other gel (C-to-P) across the gap junction, whereas it propagated from the plane side to the corner side (P-to-C) in the case of the pentagonal gel array. Numerical analysis based on the Keener-Tyson model was done for understanding the mechanism of unidirectional propagation in triangle and pentagonal gel arrays. The swelling and deswelling changes of the gels followed the unidirectional propagation of the chemical wave. 相似文献
98.
Moriyuki Sato Miyuki Notsu Shinji Nakashima Yuko Uemoto 《Macromolecular rapid communications》2001,22(9):681-686
New semi‐rigid thermotropic liquid crystalline (LC) polyesters composed of a quaterphenyl analogue of 2,2′‐bis(1,3,4‐thiadiazole) were synthesized by high‐temperature solution polycondensation of a dioxydiundecanol derivative of 5,5′‐diphenyl‐2,2′‐bis(1,3,4‐thiadiazole) with four diacyl chlorides, whose structures were characterized by FT‐IR and 13C NMR spectroscopy, as well as elemental analysis. Differential scanning calorimetry (DSC) measurements and texture observations using polarizing microscopy displayed that all the polyesters form stable enantiotropic smectic and/or nematic LC phases. Solution and solid state absorption and fluorescence spectra indicated that the polyesters show absorption maxima arising from the 2,2′‐bis(1,3,4‐thiadiazole) moiety and emit bluish green light, the Stokes shifts being 129 nm in solution and 60–64 nm in the solid state. Band gap energies of the polyesters calculated from the solid state absorption spectra were 2.67–2.82 eV. 相似文献
99.
100.
The nitro group in tertiary or secondary aliphatic nitro compounds is replaced by hydrogen or deuterium on treatment with tributyltin hydride or tributyltin deuteride, respectively. 相似文献