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81.
Shiina I Kawakita Y Ibuka R Yokoyama K Yamai YS 《Chemical communications (Cambridge, England)》2005,(32):4062-4064
An efficient method for the synthesis of (+)-buergerinin F is established via the enantioselective aldol reaction of a tetra-substituted ketene silyl acetal with crotonaldehyde, followed by intramolecular Wacker-type ketalization. 相似文献
82.
Kubo Y Tokita S Kojima Y Osano YT Matsuzaki T 《The Journal of organic chemistry》1996,61(11):3758-3765
A new family of indoaniline-derived calix[4]arenes has been synthesized for the purpose of developing a new chromogenic receptor. A condensing reaction of calix[4]arene (1) with 4-(diethylamino)-2-methylaniline hydrochloride (2) in the presence of an oxidizing agent under alkaline conditions affords mono- (3), 1,2-bis- (4), 1,3-bis- (5), and tetrakisindoaniline-derived (6) calix[4]arenes after careful column chromatography. Compound 3 is crystallized from a CHCl(3)-MeOH solution, and the crystal structure was determined by X-ray analysis. The crystal is monoclinic, space group P2(1)/n, Z = 4, a = 19.507(6) ?, b = 18.591(6) ?, c = 8.524(2) ?, beta = 94.69(2) degrees. The final R value for 2406 reflections of F(o) > 3sigma(F(o)) is 0.085. A unique intramolecular hydrogen-bonding network involving the carbonyl oxygen of indoaniline for 3 implied that the quinone carbonyl group as an acceptor of the chromophore can easily be subjected to an electrostatic interaction in the lower rim. Indeed, 1,3-bis(indoaniline)-derived 2,4-bis((ethoxycarbonyl)methoxy)calix[4]arene 7, prepared by the reaction of 5 with ethyl bromoacetate in the presence of NaH, is capable of undergoing an efficient ion-dipole interaction between the binding cation and the two quinone carbonyl groups of the chromophores, so that a selective Ca(2+)-induced pronounced color change (wavelength change > 100 nm) occurs with an association constant on the order of 10(6) in 99% EtOH, making 7 of potential use as an optical sensor for Ca(2+) detection. The IR and NMR studies have indicated that Ca(2+) is encapsulated in the cavity made by the distally located OCH(2)CO(2) groups on the lower rim of the cone-shaped calix[4]arene segment. Interestingly, however, the shape of the cavity in which Ca(2+) has been encapsulated does not have a C(2) axis of symmetry, as inferred from the (1)H-(1)H COSY experiment. On the other hand, 1,2-bis(indoaniline)-derived analogue 8 shows no response with metal ions, which can be interpreted to mean the absence of a cavity for encapsulation on the lower rim. 相似文献
83.
Kurihara H Lu X Iiduka Y Mizorogi N Slanina Z Tsuchiya T Akasaka T Nagase S 《Journal of the American Chemical Society》2011,133(8):2382-2385
Unambiguous X-ray crystallographic results of the carbene adduct of Sc(2)C(82) reveal a new carbide cluster metallofullerene with the unexpected C(2v)(5)-C(80) cage, that is, Sc(2)C(2)@C(2v)(5)-C(80). More interestingly, DFT calculations and NMR results disclose that the dynamic motion of the internal Sc(2)C(2) cluster depends strongly on temperature. At 293 K, the cluster is fixed inside the cage with two nonequivalent Sc atoms on the mirror plane, thereby leading to C(s) symmetry of the whole molecule. However, when the temperature increases to 413 K, the (13)C and (45)Sc NMR spectra show that the cluster rotates rapidly inside the C(2v)(5)-C(80) cage, featuring two equivalent Sc atoms and weaker metal-cage interactions. 相似文献
84.
Daisuke Kobayashi Yuko Endo Tadaaki Sakamoto Tomoki Takahashi Hideyuki Matsumoto Chiaki Kuroda Katsuto Otake Atsushi Shono 《Macromolecular Symposia》2013,324(1):55-61
Summary: Polypyrrole conducting polymers have been investigated widely for various applications because of their thermal and environmental stability and good electrical conductivity. Using chemical oxidative polymerization for the synthesis of polypyrrole particles, the reaction rate is very fast. In this study, we designed two new reaction fields for the synthesis of spherical polypyrrole nanoparticles. In the first system, oxidative polymerization of monomer droplets infused in a water/oil (W/O) emulsion reaction field was investigated. The second system employed dispersed monomer in an aqueous solution with a low concentration of oxidant in which polymerization was augmented by ultrasonic irradiation. Effective control of the reaction rate was important for enabling the synthesis of fine spherical polypyrrole particles. 相似文献
85.
A low-capacity cation-exchange HPLC method for the determination of UV-absorbing organic cations such as amino acids, histidine dipeptides, and creatinine was developed. A commercially available reversed-phase column was dynamically coated with hexadecylsulfonate, and was successfully used for the cation-exchange separation with ethylenediammonium eluting ion at pH 2.5. The coated column was enough stable for the specific use with a completely aqueous mobile phase at low and constant pH; and the day-to-day reproducibility for retention time was 0.9-1.7% of RSD (relative standard deviation). The linear relation between concentrations and detector responses (area) by using a photodiode-array UV detection at 210 nm ranged from 0.2 to 1000 microM (sample size 50 microl) for 1-methylhistidine, 3-methylhistidine, histidine, creatinine, anserine, carnosine, and homocarnosine, and from 0.5 to 2000 microM for creatine, tyrosine, and phenylalanine, with less than 5% of RSD. The UV spectrum (190-300 nm) obtained during chromatography was very indicative for each analyte. Overall recoveries were 97-104%. The developed HPLC method in conjunction with preliminary fractionation technique could be applied to the analysis of urine of patient with metabolic disorder such as phenylketonuria. 相似文献
86.
87.
Kazuo Yoshino Kotaro Hachiman Akihiro Yokoyama Tsutomu Yokozawa 《Journal of polymer science. Part A, Polymer chemistry》2010,48(6):1357-1363
Chain‐growth condensation polymerization of p‐aminobenzoic acid esters 1 bearing a tri(ethylene glycol) monomethyl ether side chain on the nitrogen atom was investigated by using lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) as a base. The methyl ester monomer 1a afforded polymer with low molecular weight and a broad molecular weight distribution, whereas the polymerization of the phenyl ester monomer 1b at ?20 °C yielded polymer with controlled molecular weight (Mn = 2800–13,400) and low polydispersity (Mw/Mn = 1.10–1.15). Block copolymerization of 1b and 4‐(octylamino)benzoic acid methyl ester ( 2 ) was further investigated. We found that block copolymer of poly 1b and poly 2 with defined molecular weight and low polydispersity was obtained when the polymerization of 1b was initiated with equimolar LiHMDS at ?20 °C and continued at ?50 °C, followed by addition of 2 and equimolar LiHMDS at ?10 °C. Spherical aggregates were formed when a solution of poly 1b in THF was dropped on a glass plate and dried at room temperature, although the block copolymer of poly 1b and poly 2 did not afford similar aggregates under the same conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1357–1363, 2010 相似文献
88.
89.
Yuko Okamoto Toshimasa Tanaka Hironori Kokubo 《Journal of computer-aided molecular design》2010,24(8):699-712
We performed replica-exchange molecular dynamics (REMD) simulations of six ligands to examine the dependency of their free
energy landscapes on charge parameters and solvent models. Six different charge parameter sets for each ligand were first
generated by RESP and AM1-BCC methods using three different conformations independently. RESP charges showed some conformational
dependency. On the other hand, AM1-BCC charges did not show conformational dependency and well reproduced the overall trend
of RESP charges. The free energy landscapes obtained from the REMD simulations of ligands in vacuum, Generalized-Born (GB),
and TIP3P solutions were then analyzed. We found that even small charge differences can produce qualitatively different landscapes
in vacuum condition, but the differences tend to be much smaller under GB and TIP3P conditions. The simulations in the GB
model well reproduced the landscapes in the TIP3P model using only a fraction of the computational cost. The protein-bound
ligand conformations were rarely the global minimum states, but similar conformations were found to exist in aqueous solution
without proteins in regions close to the global minimum, local minimum or intermediate states. 相似文献
90.
Bishnu Prasad Bastakoti Sudhina Guragain Yuuichi Yokoyama Shin-ichi Yusa Kenichi Nakashima 《Colloid and polymer science》2010,288(9):991-996
Organic–inorganic nanohybrid particles are prepared in aqueous solution from poly(ethylene oxide-b-sodium 2-acrylamido-1-propanesulfonate-b-styrene) (PEO-b-PAMPS-b-PS) triblock copolymer and ferric ions. The hybrid micelles were characterized by dynamic light scattering, scanning electron
microscopy, transmission electron microscopy, and zeta-potential measurements. The hydrodynamic diameter of the hybrid micelles
ranges from 68 to 118 nm depending on the concentration of the polymer and the amount of ferric ions loaded on the polymer.
Zeta-potential measurements revealed that the micelles are assembled mainly by electrostatic interaction between the ferric
ions and the negatively charged PAMPS block in the PEO-b-PAMPS-b-PS. 相似文献