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11.
[formula: see text] The total synthesis of the marine sesquiterpene quinone (+)-puupehenone, a promising new antituberculosis agent, was achieved in 10 steps starting from commercially available (+)-sclareolide. The key feature of this synthesis is the construction of the heterocycle via an intramolecular attack of the terpenoid-derived C-8 oxygen function onto an oxidatively activated 1,2-dihydroxyphenyl unit. 相似文献
12.
Geoffroy Guna Pascal Allanon Anne-Marie Cazabat 《Colloids and surfaces. A, Physicochemical and engineering aspects》2007,300(3):307-314
This paper provides experimental checks of assumptions needed in a model describing the moving contact line of a wetting droplet evaporating in an inert atmosphere. Special interest is given to the maximum extension of the droplet, when the contact line starts receding. The predicted power law dependence between the values of the radius R0 and the contact angle Θ0 at the maximum extension is checked against experiments. We find fairly good agreement with theory for very small droplets. However, discrepancies show up rapidly when the droplet size increases. 相似文献
13.
14.
The spontaneous spreading of macroscopic drops of nematic liquid crystals on hydrophilic substrates has been investigated by interferometric techniques. There is a complex interplay between the elastic energy, due to antagonist anchoring at the interfaces, and the radial flow in the spreading drop. A relevant parameter appears to be the relative humidity of the atmosphere, because it controls the amount of water molecules adsorbed on the substrate and, therefore, the strength of anchoring defects. The spreading laws differ from the ones of simple wetting liquids, and contact line instabilities coupled to short- (anchoring) or large-scale (disclinations) defects of the nematic film are observed. 相似文献
15.
A new straightforward method of synthesis of dendrimers, using two branched monomers (CA(2) and DB(2)), is described. Each generation is obtained in a single quantitative step, with only N(2) or H(2)O as byproducts; generation 4 is obtained in only four steps. The end groups are alternatively phosphines and hydrazines; their versatile reactivity is illustrated by the reaction of generation 4 with a branched CD(5) monomer, which increases the number of end groups in a single step from 48 to 250. 相似文献
16.
Kanibolotsky A Roquet S Cariou M Leriche P Turrin CO de Bettignies R Caminade AM Majoral JP Khodorkovsky V Gorgues A 《Organic letters》2004,6(13):2109-2112
[structure: see text] In four new dendrimers terminated by 12 electroactive tetrathiafulvalenyl substituents, the tridimensional character of the inter- and intradendrimeric charge and electron transfer, and hence of the electroconductivity, is evidenced by examination of the electronic spectra of their corresponding neutral state and cation radical, dication, and mixed-valence salts, including a closed-shell anion. 相似文献
17.
Max Robba Michel Cugnon De Sevricourt Anne-Marie Godard 《Journal of heterocyclic chemistry》1979,16(6):1175-1180
The cleavage of the pyridazine ring of the acyltetrahydro [1] benzofuro [2,3-d] pyridazones was carried out by hydrolysis, alcoholysis or aminolysis reactions and they affect the lactam 3,4-bond. They lead chiefly to benzofuran derivatives with acid, ester, amide or hydrazide groups in the 2-position and eventually an acylated methylhydrazine group in the 3-position. The cyclization reactions of 3-hydrazinomethylbenzofuran-2-carboxylic acid and its derivatives or ethyl 3-bromome thylbenzofuran-2-carboxylate affords tetrahydrobenzofuropyridazones. The nmr spectra were studied. 相似文献
18.
Rakotondradany F Whitehead MA Lebuis AM Sleiman HF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(19):4771-4780
A new strategy to effect photoinduced control over molecular self-assembly is reported. This strategy uses the reversible trans-cis photoisomerization of a novel azobenzene system, where the trans- and cis-forms self-assemble into dramatically different higher-order structures. The trans-azobenzene form of this molecule associates into infinite hydrogen-bonded linear tapes, while the cis-azobenzene form undergoes hydrogen-bonded self-assembly into cyclic tetramers. This results in a second level of association, where the cis-hydrogen-bonded supramolecular cycles ultimately form long, rod-like aggregates through stacking interactions. 相似文献
19.
Elhabiri M Siri O Sornosa-Tent A Albrecht-Gary AM Braunstein P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(1):134-141
We present a detailed study on the acid-base behaviour of a family of "potentially antiaromatic" p-benzoquinonediimine ligands. These 12pi electron molecules can be considered as constituted of two chemically connected but electronically not conjugated 6pi-electron subunits. Upon successive protonation, "mono" and "double" cyanine-type chromophores are generated in solution and allow a precise and sensitive spectrophotometric detection. These molecules represent a new class of tunable quinones whose electronic and structural properties can be triggered by proton input, as established by a complete physico-chemical study involving a combination of potentiometric and spectrophotometric methods (absorption and emission). 相似文献
20.
The LiHe+
n
, the NaHe+
n
, and the MgHe+
n
complexes with n=1, 2, 3, 4 were studied using ab initio calculations with the MP2/6-311+G(3df, 3pd) method. The complexes are found to be stable. For the n=1 complexes, previous results were available and the calculations performed are in good agreement with those results. This lends credibility to the results obtained for the complexes with higher n. 相似文献