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991.
Takafumi Fukushima Toshiyuki Oyama Takao Iijima Masao Tomoi Hiroshi Itatani 《Journal of polymer science. Part A, Polymer chemistry》2001,39(19):3451-3463
A soluble multiblock copolyimide without specific functional groups such as OH and COOH was prepared by a direct one‐pot polycondensation of two types of dianhydrides and diamines in the presence of γ‐valerolactone/pyridine catalyst using N‐methylpyrrolidone (NMP)/toluene mixture as a solvent. The polyimide film containing the photosensitive agent diazonaphthoquinone (DNQ) compound gave positive‐tone behavior by UV irradiation, followed by development in a mixture of ethanolamine/NMP/H2O (1/1/1 by weight). The scanning electron microscopic photograph of the resultant image showed fine patterns with about 20 μm film thickness. Its pattern forming was based on the photorearrangement of diazonaphthoquinone, a process in which the ring‐opening reaction of imide units of the polyimide with the amine used as a developer and the following degradation of the polymer are induced. Such a new imaging technique combines principles of photolithography and etching of a polyimide to give, what we call, reaction development patterning in which the main chemical reactions directly related to the pattern formation occur during development. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3451–3463, 2001 相似文献
992.
When the esters of arylboronic acids with 2,2-dimethylpropan-1,3-diol were treated with a catalytic amount of [Rh(OH)(cod)]2 in the presence of 1,3-bis(diphenylphosphino)propane and CsF in dioxane at 60 degrees C under carbon dioxide atmosphere, the benzoic acid derivatives were obtained in good yields. Reactions of alkenylboronic esters also proceeded under similar conditions to give alpha,beta-unsaturated carboxylic acids. As these boronic esters are now easily available through coupling or direct borylation reactions, this method would be a useful method for the preparation of various functionalized aryl- and alkenyl-carboxylic acids. 相似文献
993.
Han HF Nakamura N Zuo F Hirakawa A Yokozawa T Hattori M 《Chemical & pharmaceutical bulletin》2006,54(4):496-500
Mycelia of Antrodia cinnamomea were extracted with chloroform and hot water. A neutral polysaccharide named ACN2a separated from the water extract was purified using 10% CCl3COOH, and repeated column chromatography on HW-65 and DE-52 cellulose. Its structure was determined by chemical and spectroscopic analyses. ACN2a was composed of Gal, Glc, Fuc, Man and GalN (in the ratio 1:0.24:0.07:0.026:faint), in which an alpha-D-(1-->6)-Gal linkage accounted for 73% of all linkages. The ratio of branch points was about 16% of the total residual numbers, and branches were attached to C-2 of galactosyl residues of the main chain. ACN2a had an average molecular weight of 12.9x10(5) Daltons, [alpha]D25=+115 degrees (c=0.44, H2O); [eta]=0.0417dl.g-1, Cp=0.2663 cal/(g. degrees C). The hepatoprotective effect of ACN2a was evaluated using a mouse model of hepatic injury that was induced by Propionibacterium acnes (P. acnes) and lipopolysaccharide (LPS). The administration of ACN2a (0.4, 0.8 g/kg/d, p.o.), significantly prevented increases in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) enzyme activities in mice treated with P. acnes-LPS, indicating hepatoprotective activity in vivo. 相似文献
994.
Three new lignans, longipedunins A-C, from Kadsura longipedunculata and their inhibitory activity against HIV-1 protease 总被引:3,自引:0,他引:3
Sun QZ Chen DF Ding PL Ma CM Kakuda H Nakamura N Hattori M 《Chemical & pharmaceutical bulletin》2006,54(1):129-132
Three new lignans, longipedunins A (1), B (2) and C (3), together with three known compounds, benzoyl-binankadsurin A (4), acetyl-binankadsurin A (5) and schisanlactone A (6), were isolated from Kadsura longipedunculata. Their structures and stereochemistry were determined by spectral and single-crystal X-ray analyses. Compounds 1 and 6 showed appreciable inhibitory activity against HIV-1 protease with IC50 values of 50 and 20 microM, respectively. 相似文献
995.
In the asymmetric addition of allyltrichlorosilane to benzaldehyde, polystyrenes with chiral phosphoramide substituents as Lewis base catalysts showed up to 2.4 times better catalytic activity and 1.4 times higher enantioselectivity than the corresponding low-molecular-weight analogues. 相似文献
996.
Kaneko M Katakura N Harada C Takei Y Hoshino M 《Chemical communications (Cambridge, England)》2005,(27):3436-3438
Visible light decomposition of aqueous ammonia to dinitrogen was successfully achieved by using a new photocatalytic system based on a molecular photoelectron relay composed of a sensitizer (Ru(bpy)(3)2+), an electron mediator (methylviologen) and an electron acceptor (dioxygen), which can be used as a visible light-driven photocatalyst instead of UV-driven semiconductors. 相似文献
997.
Urata H Go M Ohmoto N Minoura K Akagi M 《Chemical communications (Cambridge, England)》2002,(5):544-545
Heterochiral ApAs (ALpAL and ALpAL) have been synthesized and investigation of their helical structures by means of spectroscopic techniques indicates that the chirality of the 3'-end residue is the primary factor for determining the helical sense of ApA. 相似文献
998.
AsuhaTakuya Kobayashi Masao TakahashiHitoo Iwasa Hikaru Kobayashi 《Surface science》2003,547(3):275-283
Spectroscopic and electrical properties of ultrathin silicon dioxide (SiO2) layers formed with nitric acid have been investigated. The leakage current density of the as-grown SiO2 layers of 1.3 nm thickness is high. The leakage current density is greatly decreased by post-oxidation annealing (POA) treatment at 900 °C in nitrogen, and consequently it becomes lower than those for thermally grown SiO2 layers with the same thickness. X-ray photoelectron spectroscopy measurements show that high density suboxide species are present before POA and they are markedly decreased by POA. Fourier transformed infrared absorption measurements show that water and silanol group are present in the SiO2 layers before POA but they are removed almost completely by POA above 800 °C. The atomic density of the as-grown chemical SiO2 layers is 4% lower than that of bulk SiO2 layers, while it becomes 12% higher after POA. It is concluded that the high atomic density results from the desorption of water and OH species, and oxidation of the suboxide species, both resulting in the formation of SiO2. The valence band discontinuity energy at the Si/SiO2 interface increases from 4.1 to 4.6 eV by POA at 900 °C. The high atomic density enlarges the SiO2 band-gap energy, resulting in the increase in the band discontinuity energy. The decrease in the leakage current density by POA is attributed to (i) a reduction in the tunneling probability of charge carriers through SiO2 by the enlargement of the band discontinuity energy, (ii) elimination of trap states in SiO2, and (iii) elimination of interface states. 相似文献
999.
Masao Kaneko 《Journal of Chemical Sciences》1992,104(6):723-730
The amphiphilic porphinato zinc(II) complex (ZnP) containing four substituted amphiphilic alkyl chains was embedded in the
liposomes of l,2-dipalmitoyl-sn-glycero-3phosphocholine. The distance from the embedded ZnP to the outer phase was changed from 9 to 27 ? by changing the
substituted alkyl chain length. The electron transfer from the excited Zn complex to methylviologen (MV2+) or benzoquinone (BQ) added in the outer aqueous phase was studied. At first, quenching reactions were analyzed based on
dynamic and static reaction models of the excited state. For the MV2+ quencher, only the triplet excited state of the embedded ZnP reacted, and electron transfer occurred at a distance less than
12 ?. In BQ both the singlet and the triplet excited states reacted, and the reaction of the singlet state was a static one
indicating that BQ is incorporated into the liposomes. The distribution of the BQ molecule in the quenching sphere of ZnP
was presented based on calculations assuming a stepwise incorporation into the quenching sphere. 相似文献
1000.
An analytical interpretation is made for the Monte Carlo results on the shape of an unrestricted random flight chain. Both the average shape and the time correlation function of the shape fluctuation are discussed. The Monte Carlo results are well reproduced by assuming that the shape of the chain is primarily determined by the first few normal modes. 相似文献