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21.
Juglomycin A has been synthesized in four steps from 5-methoxy-1-naphthol. 相似文献
22.
Reaction of trienes with α,β-unsaturated aldehydes produces bicyclic products via a tandem Diels-Alder/ene reaction. The adduct from tiglic aldehyde was converted into isoligularone by conversion to a furan followed by benzylic oxidation. 相似文献
23.
Lewis acid-mediated Diels-Alder reactions of quinol lactone 2 gave regioselectivity opposite to that of the uncatalyzed reaction. Compound 12 is proposed as the reactive intermediate generated by the reaction of 2 with stannic chloride. 相似文献
24.
A new phenolic glucoside gallate, vanillic acid 4-O-beta-D-(6'-O-galloyl) glucopyranoside (1) was isolated from the bark of Terminalia macroptera Guill.et Perr., together with 3,3',4'-tri-O-methylellagic acid (2) and two triterpene glucopyranosyl esters, 24-deoxysericoside (3) and chebuloside II (4). Compounds 2-4, not described previously for this plant, showed antimicrobial activities against Bacillus subtilis, while 3 and 4 possessed haemolytic properties. In both assays 1 was found to be inactive. 相似文献
25.
26.
The nonlinear integro-differential equation, obtained from the coupled Maxwell-Dirac equations by eliminating the potential A, is solved by iteration rather than perturbation. The energy shift is complex, the imaginary part giving the spontaneous emission. Both self-energy and vacuum polarization terms are obtained. All results, including renormalization terms, are finite. 相似文献
27.
Cs[Na(NH3)6][B10H10]·NH3 was synthesised from cesium and disodium‐decahydro‐closo‐decaborate Na2B10H10 in liquid ammonia, from which it crystallized in form of temperature sensitive colorless plates (triclinic, P1¯, a = 8.4787(7) Å, b = 13.272(1) Å, c = 17.139(2) Å, α = 88.564(1)°, β = 89.773(1)°, γ = 81.630(1)°, V = 1907.5(3) Å3, Z = 4). The compound is the first example of an alkali metal boranate with two different types of cations. The decahydro‐closo‐decaborate dianions [B10H10]2— and the cesium cations form a equation/tex2gif-stack-1.gif[Cs2(B10H10)2]2— layer parallel to the ac plane. These layers are separated by N—H···N‐hydrogen bonded hexamminesodium cations. 相似文献
28.
Th Kraus 《Monatshefte für Chemie / Chemical Monthly》1964,95(3):733-738
Zusammenfassung Die Dampfdruckerniedrigung, die kondesierendes Argon bei 4,2° K auf Wasserstoff ausübt, wurde unter der Annahme, da die Stammfunktion desRaoultschen Gesetzes unter den herrschenden Bedingungen gültig ist, berechnet und mit Mewerten vonHengevoss undTrendelenburg verglichen. Aus der guten Übereinstimmung der Ergebnisse kann mit gro Wahrscheinlichkeit auf die Richtigkeit dieser Voraussetzungen geschlossen werden. 相似文献
29.
This work is part of an effort to develop chelating agents for stable binding and easy conjugation of Re-188 to biologically interesting structures. Starting from the well-known in vivo stability of [(188)ReO(DMSA)(2)](-), we want to exploit this coordination system for the design of (188)ReO(V) chelates, which are stable toward reoxidation to perrhenate and toward ligand exchange under all conditions of radiopharmaceutical development. Therefore, a new type of tetradentate ligand has been synthesized by bridging two molecules of N,N'-diisobutyl-2,3-dimercaptosuccinamide with N-(3-aminopropyl)propane-1,3-diamine. The resulting stereoisomeric tetrathiolato S(4) ligand of composition ((i)()Bu)(2)N(O)C-C(SH)-C(SH)-C(O)NH-(CH(2))(3)-NH-(CH(2))(3)-NHC(O)-C(SH)-C(SH)-C(O)N((i)Bu)(2) forms anionic five-coordinate oxorhenium(V) complexes by a ligand-exchange reaction of NBu(4)[ReOCl(4)] in methanol. In the absence of a base, the compounds were isolated as "betaine", [ReO(S(4))], with the protonated nitrogen of the bridge serving as an internal "counterion". Two representatives have been fully characterized in both the solid and solution states and found to adopt the expected square-pyramidal coordination geometry. The equatorial plane is formed by four thiolate sulfur atoms, whereas the oxygen occupies the apical position. The orientation of the metal oxo group is exo in relation to the carbamido groups in both isomers. Both complexes are stereoisomeric regarding the junction of the triamine chain. 相似文献
30.
Kraus M Janek K Bienert M Krause E 《Rapid communications in mass spectrometry : RCM》2000,14(13):1094-1104
The self-assembly of beta-sheet peptide domains resulting in the formation of fibrillar aggregates (amyloids) is a feature of various neurodegenerative disorders. In order to evaluate mass spectrometric methods for the characterization of intermolecular beta-sheet structures the hydrogen/deuterium exchange behaviour of model peptides DPKGDPKG-(VT)(n)-GKGDPKPD-amide (n = 3,4,5,6,7,8), (VT)(n)-peptides, composed of a central beta-sheet-forming domain and N- and C-terminal nonstructured octapeptide sequences, was measured by electrospray ionization mass spectrometry (ESI-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The kinetic analysis of the hydrogen/deuterium exchange (HX) shows that intermolecular beta-sheet structures contain slowly exchanging protons (k =0.001 1/min). Localization of beta-sheet domains was achieved by monitoring the hydrogen exchange of peptide fragments generated via collision-induced dissociation (CID) or post source decay (PSD). The hydrogen exchange kinetics and the beta-sheet domains determined by ESI- and MALDI-MS were found to correlate with the length and stability of the beta-structure domain of the (VT)(n)-peptides. 相似文献