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11.
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Köhler B Enkelmann V Oda M Pieraccini S Spada GP Scherf U 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(14):3000-3004
Novel chiral macrocycles consisting of two rigid oligoarylene rods and two chiral spiroindane clips have been synthesized by condensation of spiroindane diols and CF3-activated alpha-omega-difluorooligoaryls. Since a broad variety of planar aromatic macrocycles is known, our non-planar, chiral rings represent a new class of macrocyclic compounds. The first two examples, which contain quaterphenylene and diphenylbithiophene rods, are presented in this communication; for one of them a crystal structure is given. The chiroptical properties of the macrocycles can be interpreted as an interplay of the "intra-rod" helicity of individual oligoarylene rods and the "inter-rod" helicity between both chromophores of the macrocycle. The macrocycles can act as chiral dopands of commercially available, and novel, polymeric nematic liquid crystals (emissive polyfluorenes). The "intra-rod" helicity of individual oligoarylene rods is the main feature in determining the resulting helical twisting power (HTP). The cholestric induction in mesogenic, emissive polyfluorenes is of special interest for a realization of electronic devices that have a circularly polarized electroluminescence. The results are also important for an understanding of larger ensembles of chiral rodlike molecules, especially their pi-pi interactions. 相似文献
13.
Tulipa gesneriana lectin-erythrocyte (TGL-E) which agglutinates mouse erythrocytes showed a potent mitogenic activity on mouse spleen cells and human peripheral blood lymphocytes, however, TGL-E had only slight mitogenic activity on mouse thymus cells. Its subunit alpha with a molecular weight (MW) of about 26,000 showed a potent mitogenic activity as did that of native lectin, but subunit beta with a MW of about 14,000 showed no activity, indicating that the mitogenic activity of TGL-E originates from subunit alpha. TGL-E stimulated T cell enriched spleen cells which passed through a nylon column, but not spleen cells from a nude mouse or spleen cells treated with anti-Thy 1.2 antibody and complement. Thus, TGL-E stimulates only mouse T cells but not B cells. The other lectin in tulip bulbs, Tulipa gesneriana lectin-yeast showed no mitogenic activity on mouse spleen, thymus cells or human paripheral blood lymphocytes. 相似文献
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[reaction: see text] Triethylborane-induced hydrometalation of alkynes proceeds in an anti manner to afford the corresponding (Z)-alkenylmetal compounds stereoselectively, where dichloroindium hydride would play a key role. A variety of functional groups including hydroxy, carbonyl, and carboxy groups were tolerant under the reaction conditions. Following iodolysis and cross-coupling reaction of the (Z)-alkenylmetal species show the usefulness of this strategy. 相似文献
16.
Stabilization of the spark-discharge point on a sample surface by laser irradiation for steel analysis. 总被引:1,自引:0,他引:1
A combined technique with laser irradiation is suggested to control spark discharge for analytical use, having a unique feature that firing points of the spark discharge can be fixed by laser irradiation. Because the spark discharge easily initiates at particular surface sites, such as non-metallic inclusions, called selective discharge, the concentration of some elements sometimes deviates from their average one in spark discharge optical emission spectrometry. Therefore, stabilization of firing points on a sample surface could improve the analytical precision. 相似文献
17.
The titled [3]radialenes are the first, water-soluble hexaaryl[3]radialenes with considerably high electron affinity, their alkali metal reduction giving rise to anion-radicals and dianions stepwise as fairly stable species in degassed tetrahydrofuran. 相似文献
18.
(-)-Pestalotin [(6S, l'S)-6-(1'-hydroxypentyl)-4-methoxy-5,6-d dihydro-2-pyrone 1a]and its three other stereoisomers were synthesized either by utilizing the Sharpless asymmetric epoxidation as the keystep or by derivation from D-(+)-glyceraldehyde acetonide. 相似文献
19.
Katayama H Ishihama Y Oda Y Asakawa N 《Rapid communications in mass spectrometry : RCM》2000,14(14):1167-1178
A novel method for electrophoretic mobility-assisted identifications of proteins, using capillary electrophoresis/mass spectrometry (CE/MS) under methanolic conditions, was developed. The number of functional groups of the enzymatic digest peptides was estimated from a single run CE/MS analysis and utilized as an additional tag for database searching in addition to the mass map of the peptides. The additional amino acid information thus obtained can improve the confidence level of the protein identification. The database searching software algorithm ProFound was modified to accept the tag, based on this new concept. In this study, optimization of the CE/MS conditions for the estimation of basic functional groups was performed as an example. An accurate value of the number of such functional groups was obtained from CE characteristics when methanolic buffer (methanol/formic acid/water = 60:20:20) was used, via an excellent correlation (r = 0.997) between the number of functional groups of the peptides and [MW((2/3))]. The mass spectrometry sensitivity was also improved when using the methanolic buffer in comparison with that obtained using aqueous 1% formic acid buffer. The identification of a protein of Saccharomyces cerevisiae, which was separated by two-dimensional electrophoresis, was performed using the methanolic buffer in combination with sheathless nanoelectrospray CE/MS. A protein spot that had not been identified by MALDI-TOFMS and LC/MS/MS was successfully identified using this new method. 相似文献
20.
A new strategy using a BINOL derivative as a chiral leaving group and Lewis acid has been developed for enantioselective alkylation of prochiral olefins. (R)-2,2'-Bis[2-(trimethylsilyl)ethoxymethyl]-1,1'-binaphthol is demonstrated to be an effective reagent for enantioselective hydroxymethylation of silyl enol ethers and trisubstituted alkenes. Electrophilic addition to prochiral olefins is accompanied by cleavage of an acetal that is dual activated by SnCl4 and the delta-effect of silicon through the S(N)2 substitution process. Enantioselective synthesis of cyclic terpenes is also described using this strategy. 相似文献