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151.
[structure: see text] 8,11-Dideoxytetrodotoxin, an unnatural tetrodotoxin analogue, was synthesized in a highly stereoselective manner from a common intermediate in our synthetic studies on tetrodotoxin. The synthesis features neighboring group participation of trichloroacetamide for stereoselective hydroxylation, protection of ortho ester, and guanidine installation with Boc-protected isothiourea. 相似文献
152.
Masahiro Yoshida 《Tetrahedron letters》2004,45(29):5573-5575
The direct coupling of propargylic alcohols with arylboronic acids has been achieved using palladium catalyst. Various propargylic alcohols and arylboronic acids can be coupled to afford the corresponding allenic and propargylic arenes, which are selectively produced depending on the substituent on the propargylic alcohol, respectively. 相似文献
153.
Masahiro Yoshida 《Tetrahedron letters》2004,45(9):1861-1864
Substituted 2,3-dihydrofurans and benzofurans are synthesized by the palladium-catalyzed reaction of 5-methoxycarbonyloxy-3-pentyn-1-ols and 1-(2-hydroxyphenyl)-3-methoxycarbonyloxy-1-propyne with nucleophiles, respectively. Various substituted propargylic carbonates and nucleophiles are efficiently transformed to their corresponding products. Additionally, a reaction using substrates containing a nucleophilic phenoxy group within the same molecule also produces the corresponding dihydrofuran. 相似文献
154.
Toshiki Yoshizawa Michika Onoda Takeshi Ueki Ryota Tamate Aya Mizutani Akimoto Ryo Yoshida 《Angewandte Chemie (International ed. in English)》2020,59(10):3871-3875
Various biological behaviors are fueled by “respiration”, which is an example of catabolism. So far, we have reported various self‐oscillating soft materials exhibiting bioinspired dynamic movements. These autonomous polymer systems are driven by the Belousov–Zhabotinsky (BZ) reaction, which is analogous to the tricarboxylic acid (TCA) cycle that is an integral part of respiration. However, in the BZ reaction, the external addition of an oxidizing agent is necessary to initiate the oxidation process, which is realized by intracellular moieties such as ubiquinone in living systems. Herein, we realized self‐oscillating micelles that are driven without the external addition of an oxidizing agent. This was achieved by embedding the oxidizing source into the structure of the self‐oscillating AB diblock copolymers. This strategy introduces a new function equivalent to intracellular oxidizing moieties, and is useful for the design of completely autonomous bioinspired materials. 相似文献
155.
156.
Summary: The polylactide‐based nano‐composites were prepared via melt extrusion method using different types of intercalants and nano‐fillers having different surface charge density. In order to understand the direct polymer melt intercalation into the nano‐galleries, the interdigitated layer structure of the organically modified layered filler (OMLF), where the intercalants are oriented with some inclination to the host layer in the interlayer space, was proposed. After polymer melt intercalation, the smaller initial interlayer opening led to the larger interlayer expansion, suggesting the large amount of the intercalation of the polymer chains. Consequently, the nano‐composite exhibited finer dispersion of the nano‐fillers when compared with the nano‐composites prepared from OMLFs with larger initial interlayer opening.
157.
Prof. Isao Fujii Dr. Makoto Hashimoto Kaori Konishi Akiko Unezawa Haruka Sakuraba Kenta Suzuki Harue Tsushima Miho Iwasaki Satsuki Yoshida Akane Kudo Rina Fujita Aika Hichiwa Koharu Saito Dr. Takashi Asano Dr. Jun Ishikawa Dr. Daigo Wakana Dr. Yukihiro Goda Ayumi Watanabe Mamoru Watanabe Yui Masumoto Dr. Junichiro Kanazawa Dr. Hajime Sato Prof. Masanobu Uchiyama 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(22):8542-8548
Shimalactones A and B are neuritogenic polyketides possessing characteristic oxabicyclo[2.2.1]heptane and bicyclo[4.2.0]octadiene ring systems that are produced by the marine fungus Emericella variecolor GF10. We identified a candidate biosynthetic gene cluster and conducted heterologous expression analysis. Expression of ShmA polyketide synthase in Aspergillus oryzae resulted in the production of preshimalactone. Aspergillus oryzae and Saccharomyces cerevisiae transformants expressing ShmA and ShmB produced shimalactones A and B, thus suggesting that the double bicyclo-ring formation reactions proceed non-enzymatically from preshimalactone epoxide. DFT calculations strongly support the idea that oxabicyclo-ring formation and 8π-6π electrocyclization proceed spontaneously after opening of the preshimalactone epoxide ring through protonation. We confirmed the formation of preshimalactone epoxide in vitro, followed by its non-enzymatic conversion to shimalactones in the dark. 相似文献
158.
Daisuke Saito Dr. Tomohiro Ogawa Dr. Masaki Yoshida Junichi Takayama Dr. Satoshi Hiura Prof. Dr. Akihiro Murayama Dr. Atsushi Kobayashi Prof. Dr. Masako Kato 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18882-18889
A series of assembled PtII complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)2(R-impy)] (R-impyH+=1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me ( Pt-Me ), Et ( Pt-Et ), iPr ( Pt- i Pr ), and tBu ( Pt- t Bu )). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51–0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (3MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt- t Bu . Importantly, Pt- t Bu is the first example that exhibits blue 3MMLCT emission. The 3MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the 3MMLCT emission presents a new strategy of superfine control of the emission color. 相似文献
159.
Nobutaka Yoshimura Dr. Atsushi Kobayashi Dr. Masaki Yoshida Prof. Masako Kato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(70):16939-16946
To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of RuII-photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO2 nanoparticles with different surface structures, Zr- RuCP6 -Zr- RuP6 @N wt %Pt-TiO2, RuCP6 -Zr- RuP6 @N wt %Pt-TiO2, and RuCP2 -Zr- RuP6 @N wt %Pt-TiO2 (N=0.2, 1, and 5), and evaluated their photocatalytic H2 evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I− to the photo-oxidized RuIII PS is comparable, the activity increased in the following order: RuCP2 -Zr- RuP6 @1 wt %Pt-TiO2 < RuCP6 -Zr- RuP6 @1 wt %Pt-TiO2 < Zr- RuCP6 -Zr- RuP6 @1 wt %Pt-TiO2. The apparent quantum yield of Zr- RuCP6 -Zr- RuP6 @1 wt %Pt-TiO2 in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr4+-phosphate groups attracted I− anions to the nanoparticle–solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators. 相似文献
160.
Imahori H Mitamura K Umeyama T Hosomizu K Matano Y Yoshida K Isoda S 《Chemical communications (Cambridge, England)》2006,(4):406-408
A silica microparticle has been successfully employed as a nanoscaffold to self-organize porphyrin and C60 molecules on a nanostructured SnO2 electrode which exhibits efficient photocurrent generation. 相似文献