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1.
Haruka Takeuchi Prof. Dr. Shinsuke Inuki Kohei Nakagawa Takaaki Kawabe Dr. Atsuhiko Ichimura Prof. Dr. Shinya Oishi Prof. Dr. Hiroaki Ohno 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21396-21401
We report herein a nonbiomimetic strategy for the total synthesis of the plicamine-type alkaloids zephycarinatines C and D. The key feature of the synthesis is a stereoselective reductive radical ipso-cyclization using visible-light-mediated photoredox catalysis. This cyclization enabled the construction of a 6,6-spirocyclic core structure through the addition of a carbon-centered radical onto the aromatic ring. Biological evaluation of zephycarinatines and their derivatives revealed that the synthetic derivative with a keto group displays moderate inhibitory activity against LPS-induced NO production. This approach could offer future opportunities to expand the chemical diversity of plicamine-type alkaloids as well as providing useful intermediates for their syntheses. 相似文献
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3.
Nishio Yu Komori Kohei Izawa Seiichiro Fukunishi Yu 《Theoretical and Computational Fluid Dynamics》2020,34(1):105-117
Theoretical and Computational Fluid Dynamics - The present study aims to simulate a collision of two droplets containing immiscible liquids by employing a three- dimensional incompressible smoothed... 相似文献
4.
Dr. Tatsuya Nishimaru Dr. Kohei Eto Dr. Keita Komine Prof. Dr. Jun Ishihara Prof. Dr. Susumi Hatakeyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7927-7934
The first total synthesis of lajollamycin B, a structurally novel nitro-tetraene spiro-β-lactone/γ-lactone antibiotic, is described. The convergent synthesis involves the construction of the C8′–C11′ nitrodienylstannane and its coupling with the segment prepared from the C1′–C7′ ω-iodoheptadienoic acid and the right-hand heterocyclic fragment, which has been utilized for our previous syntheses of oxazolomycin A. The revision of the geometry of the terminal Δ10′, 11′-double bond from E to Z is also described for the structure of natural lajollamycin B. 相似文献
5.
Shunsuke Shimo Dr. Kohei Takahashi Prof. Nobuharu Iwasawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3790-3794
A new chiral probe molecule for mono-alcohols is developed by using 1,2-dihydro-1-hydroxy-2,3,1-benzodiazaborine (DAB) bearing an acridine moiety 1 . In the presence of mono-alcohols, DAB 1 forms borate 2 by boronic ester formation, followed by coordination of the acridine moiety to the boron atom. Borate 2 has a chiral center on the boron atom and works as a stereodynamic circular dichroism (CD) probe molecule for chiral mono-alcohols based on the π–π interaction between the acridine moiety and the carbon–carbon unsaturated moiety on mono-alcohols. 相似文献
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7.
Atsushi Sato Shimpei Okubo Kazuhiro Asai Shoken Ishii Kohei Mizutani 《Applied physics. B, Lasers and optics》2014,117(2):621-631
The effect of lower-laser-level lifetimes on Q-switched pulse generation in a dual-wavelength solid-state laser with a common upper laser level was numerically and experimentally investigated. A rate-equation model that accounts for finite lower-laser-level lifetimes was developed, and for a Nd:YAG laser operating at 1064 and 1319 nm, numerical simulations of dual-wavelength pulse generation were performed with and without the effects of lower-laser-level lifetimes. In the laser experiments, characteristics of the dual-wavelength Q-switched pulses agree reasonably well with theoretical predictions. As a result, we found that both the total energy of the two Q-switched pulses and the ratio of 1064–1319-nm pulse energies were strongly affected by the lower-laser-level lifetimes when the Q-switched pulse width was comparable or shorter than the lower-laser-level lifetime. 相似文献
8.
Hirokazu Okuda Kohei Taniguchi Shinsuke Inagi Toshio Fuchigami 《Electroanalysis》2021,33(11):2296-2301
Electrochemical oxidation of O-(4-chlorobenzyl) S-methyl dithiocarbonate using tris(2,4-dibromophenyl)amine as a redox mediator was studied by cyclic voltammetric measurements. The triarylamine mediated anodic fluorodesulfurization of O-(4-chlorobenzyl) and O-(4-bromobenzyl) S-methyl dithiocarbonates provided 4-chloro- and 4-bromobenzyl fluorides, respectively in moderate yields. On the other hand, similar anodic fluorination of O-(2-phenethyl) S-octyl dithiocarbonate and O-(4-bromophenyl) S-methyl dithiocarbonate afforded 2-phenethyl trifluoromethyl ether and difluoro(methylthio)methyl 4-bromophenyl ether, respectively. Mechanistic aspects are also discussed. 相似文献
9.
Dr. Shinichiro Fuse Ayako Ikebe Kazuya Oosumi Tomoya Karasawa Keisuke Matsumura Dr. Miho Izumikawa Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Kazuo Shin‐ya Prof. Takayuki Doi Prof. Takashi Takahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9454-9460
An asymmetric total synthesis of ent‐pyripyropene A was achieved by a convergent synthetic route. We used our originally developed TiIII‐catalyzed radical cyclization to construct an AB‐ring portion that consisted of a trans‐decalin skeleton with five contiguous stereogenic centers. The coupling between the AB‐ring and the DE‐ring portions, and a subsequent C‐ring cyclization, led to the total synthesis of ent‐pyripyropene A. An evaluation of the insecticidal activity of ent‐pyripyropene A against two aphid species revealed that ent‐pyripyropene A was 35–175 times less active than naturally occurring pyripyropene A. This result indicated that the biological target of pyripyropene A recognizes the absolute configuration of pyripyropene A. 相似文献
10.
Directing/Protecting‐Group‐Free Synthesis of Tetraaryl‐Substituted Pyrazoles through Four Direct Arylations on an Unsubstituted Pyrazole Scaffold 下载免费PDF全文
Dr. Shinichiro Fuse Taiki Morita Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Hiroshi Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14370-14375
A directing/protecting‐group‐free synthesis of 1,3,4,5‐tetraaryl‐substituted pyrazoles was achieved through four transition metal‐catalyzed direct arylations. Various pyrazoles with four different aryl rings were obtained using readily available reagents from an unsubstituted pyrazole. Two aryl‐substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf=0.68, 0.64), and large Stokes shifts (19000, 15200 cm?1). 相似文献