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561.
Takeya T Kondo H Otsuka T Doi H Okamoto I Kotani E 《Chemical & pharmaceutical bulletin》2005,53(2):199-206
We investigated the reactions of various 1-naphthols (NPOHs; 1) with p-benzoquinones (Qs), such as 1,4-benzoquinone (BQ) and p-chloranil (CA), as pi-electron acceptors. With electron-rich NPOHs 1a-c, oxidative biaryl coupling and subsequent dehydrogenation reaction took place selectively to give the corresponding 2,2'-binapthyl-1,1'-quinones 3a-c in excellent yield. In the case of electron-deficient NPOHs 1e, f, two different types of reactions occurred in the presence of SnCl4 and ZrO2 under similar conditions: SnCl4 mediated oxidative dimerization and trimerization of NPOH, while ZrO2 promoted electrophilic arylation of Qs with NPOH. The resulting products 3 would be useful synthetic intermediates for naturally occurring diosindigo B, biramentaceone and violet-quinone. 相似文献
562.
563.
Qun Chen Takeyoshi Yamada Hiromichi Kurosu Isao Ando Takeshi Shiono Yoshiharu Doi 《Journal of Polymer Science.Polymer Physics》1992,30(6):591-601
The 13C spin-lattice relaxation times T1 of 13C-labeled polyethylene crystallized under different conditions were measured at temperatures from ?120 to 44°C by variable-temperature solid-state high-resolution 13C nuclear magnetic resonance (NMR) spectroscopy, in order to determine accurately the dynamics of the noncrystalline region of the polymer. From these results, it was found that the T1 minimum for the CH2 carbons in the noncrystalline region of solution-crystallized polyethylene with high crystallinity appears at higher temperature by about 20°C than that of melt-quenched polyethylene with low crystallinity. This means that the molecular motion of the CH2 carbons in the noncrystalline regions is more constrained at a given temperature in the material of higher crystallinity. Furthermore, dynamics of the noncrystalline region is discussed in terms of the 13C dipolar dephasing times. 相似文献
564.
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
565.
566.
Miscible blends of PHB and CAB were prepared by the solvent-casting method with various blend compositions, and their orientation behavior was investigated during uniaxial drawing. X-ray analysis revealed that the orientation of the crystallizable PHB component in the drawn PHB/CAB blends was changed from c-axis-orientation to a-axis-orientation with increasing CAB content. The a-axis-orientation was a result from the a-axis-oriented crystal growth caused by the intramolecular nucleation and the confined crystal growth. For quantitative assessment of the chain orientation, the Hermans orientation functions of the two respective components were obtained from the polarized FT-IR measurements. The orientation function of pure PHB stretched to 5 times of its initial length was approximately 0.8. However the value decreased rapidly with increasing CAB content, and it turned to a negative value from 30 wt.-% CAB content. This indicates that the PHB chains were aligned perpendicular to the drawing direction. On the contrary, the value of the CAB component remained almost unchanged at about 0.1 regardless of the blend composition and the annealing time, indicating that the CAB chains were constantly oriented parallel to the drawing direction without any chain relaxation. In addition, SAXS analysis suggested that the lamellar stacking direction also changed from parallel to perpendicular in the stretching direction with increasing CAB content. 相似文献
567.
A new strategy for bacterial polyhydroxyalkanoate (PHA) production by recombinant Ralstonia eutropha PHB(-)4 harboring mutated PHA synthase genes (phaC(Ac)) from Aeromona caviae was investigated. The strain harboring wild-type phaC(Ac) gene produced a PHA copolymer consisting of (R)-3-hydroxybutyrate and (R)-3-hydroxyhexanoate [P(3HB-co-3HHx)] with 3.5 mol-% of 3HHx fraction from soybean oil. When the mutants of phaC(Ac) gene were applied to this production system, 3HHx fraction in copolymers was varied in the range of 0-5.1 mol-%. Thus, the regulation of PHA copolymer compositions has been achieved by the use of mutated PHA synthase genes. 相似文献
568.
Highly oriented aragonite nanocrystal-biopolymer composites in an aragonite brick of the nacreous layer of Pinctada fucata 总被引:3,自引:0,他引:3
Takahashi K Yamamoto H Onoda A Doi M Inaba T Chiba M Kobayashi A Taguchi T Okamura TA Ueyama N 《Chemical communications (Cambridge, England)》2004,(8):996-997
13C CP/MAS NMR and FE/TEM measurements of the aragonite brick of the nacreous layer of Pinctada fucata indicate that it assembles with highly oriented aragonite nanocrystals, which are regulated by biopolymers. 相似文献
569.
570.
Cyclodextrin-enclosed substances of Brazilian propolis 总被引:1,自引:0,他引:1
Nafady AM El-Shanawany MA Mohamed MH Hassanean HA Nohara T Yoshimitsu H Ono M Sugimoto H Doi S Sasaki K Kuroda H 《Chemical & pharmaceutical bulletin》2003,51(8):984-985
By using beta-cyclodextrin-inclusion as a unique technique, an efficient separation of pharmacologically active phenolic compounds from Brazilian propolis was achieved to provide one new compound, 3-(3-hydroxy-3-methyl-butyl)-5-prenyl-4-hydroxycinnamic acid, together with two common cinnamic acid derivatives, artepillin C and capillartemisin A, and two known flavanols, aromadendrin and 3,5,7-trihydroxy-4'-methoxyflavanol. 相似文献