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291.
Johnson TA Amagata T Oliver AG Tenney K Valeriote FA Crews P 《The Journal of organic chemistry》2008,73(18):7255-7259
A reinvestigation of a Fijian collection of Cacospongia mycofijiensis has yielded the known mycothiazole and a novel heterocyclic, CTP-431 (1). Its structure including absolute configuration as 8R,9R,10S,13S was established using NMR data, calculated DFT (13)C chemical shifts and results from X-ray crystallography. It is possible that the tricyclic skeleton of CTP-431 (1) is biosynthetically related to the macrolide latrunculin A, however the thiopyrone moiety of 1 has no previous precedent in natural products chemistry. 相似文献
292.
Nara J Kajiyama H Hashizume T Suwa Y Heike S Matsuura S Hitosugi T Ohno T 《Physical review letters》2008,100(2):026102
The formation mechanism of one-dimensional Si islands on a H/Si(001)-(2x1) surface is studied using scanning tunneling microscopy/spectroscopy and first-principles calculations. We observed that one-dimensional islands that are made from dimer chains are formed at the initial growth stages similar to the bare Si(001) surface. It is found that the number of odd-numbered dimer chains is larger than that of even-numbered dimer chains. We propose the growth processes of the two types of growth edges to explain the observation. 相似文献
293.
294.
295.
Taro Fujisawa 《Compositio Mathematica》1999,115(2):129-183
We define the notion of a morphism of generalized semi-stable type, which is a generalization of the notion of a semistable degeneration over a curve. We partially generalize Steenbrink's results on the limit of Hodge structures to the case of such a morphism. As an application we prove the E1-degeneration of the relative Hodge–De Rham spectral sequence for this case. 相似文献
296.
Bunsow Nagasaka Taro Eguchi Hirokazu Nakayama Nobuo Nakamura Yasuo Ito 《Radiation Physics and Chemistry》2000,58(5-6):581-585
The existence and the average size of free volume in bisphenol-A polycarbonate (PC), low-density polyethylene (LDPE), poly (2,6-dimethyl-phenyleneoxide)(PPO), and polytetrafluoroethylene (PTFE) were studied by positron annihilation and 129Xe NMR measurements. The 129Xe NMR chemical shifts for xenon adsorbed in the polymers indicated that the average pore size of the free volume increased in the following order: PC, LDPE, PPO, and PTFE. This order of the pore size of the free volume agrees well with that estimated from the longest lifetime (τ3) of ortho-positronium formed in the polymers. The unique correlation that δ−1∝ r is established between the 129Xe NMR chemical shift (δ) and the pore size (r), which is deduced from the positron annihilation measurements. 相似文献
297.
Satoshi Honda Minami Oka Hideaki Takagi Taro Toyota 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):150-154
Repeatable topological transformation of polymers for the modulation of material functions is a challenge. We have developed a method for repeatedly resetting a cyclic macromolecular architecture to a linear architecture by photostimulation, namely, topology‐reset execution (T‐rex) based on the photochemistry of hexaarylbiimidazoles (HABIs). We synthesized cyclic poly(dimethylsiloxane)s (PDMSs) of various ring sizes with HABIs linked in the chains. UV irradiation of the cyclic PDMSs produced telechelic linear PDMSs with triphenylimidazolyl radical (TPIR) end groups. After termination of UV irradiation, end‐to‐end recyclization occurred by the recoupling of TPIRs. The cyclic PDMSs also responded to ultrasound, which decreased their molecular weight (MW) by site‐specific cleavage of in‐chain HABI moieties, and we are able to reset the MWs by subsequent phototriggered T‐rex. Furthermore, T‐rex enabled solvent‐free switching of the rheological properties of the materials while retaining the liquid character of PDMS. 相似文献
298.
Tomohiro Higashi Hiroshi Nishiyama Yohichi Suzuki Yutaka Sasaki Takashi Hisatomi Masao Katayama Tsutomu Minegishi Kazuhiko Seki Taro Yamada Kazunari Domen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2322-2326
Photoelectrochemical water splitting is regarded as a promising approach to the production of hydrogen, and the development of efficient photoelectrodes is one aspect of realizing practical systems. In this work, transparent Ta3N5 photoanodes were fabricated on n‐type GaN/sapphire substrates to promote O2 evolution in tandem with a photocathode, to realize overall water splitting. Following the incorporation of an underlying GaN layer, a photocurrent of 6.3 mA cm?2 was achieved at 1.23 V vs. a reversible hydrogen electrode. The transparency of Ta3N5 to wavelengths longer than 600 nm allowed incoming solar light to be transmitted to a CuInSe2 (CIS), which absorbs up to 1100 nm. A stand‐alone tandem cell with a serially‐connected dual‐CIS unit terminated with a Pt/Ni electrode was thus constructed for H2 evolution. This tandem cell exhibited a solar‐to‐hydrogen energy conversion efficiency greater than 7 % at the initial stage of the reaction. 相似文献
299.
Shogo Murakami Taro Sonehara Kousuke Iwakami Hiroaki Tsuji Motoi Kawatsura 《Tetrahedron letters》2019,60(8):598-601
We investigated the palladium-catalyzed [2?+?2?+?1] cycloaddition of aryl- and trifluoromethyl-group-substituted internal alkynes and carbon monoxide, and revealed that the PdBr2 effectively catalyzed the intended reaction. The PdBr2-catalyzed reaction smoothly proceeded and provided aryl- and trifluoromethyl-group-containing cyclopentadienone derivatives in up to 92% yield. 相似文献
300.
Taro Kono Ryosuke Sasaki Hideki Goto Masatoshi Kakuno Yoo Tanabe 《Molecules (Basel, Switzerland)》2021,26(22)
TiCl4 (or SnCl4)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thiophene cores, in contrast to traditional methods of thiophene formation from benzene cores. The stereocongested (less reactive) Cl position in the obtained 4-chlorobenzothiophenes functioned successfully as the partners of three cross-coupling reactions: (i) a Suzuki–Miyaura cross-couplings using Pd(OAc)2/SPhos/K3PO4 catalysis (seven examples; 63–91%), (ii) a hydroxylation using KOH/Pd(dba)2/tBu-XPhos catalysis (85%), and (iii) a borylation using a B2(pin)2/Pd(dba)2/XPhos/NaOAc catalysis-provided 4-(pin)B-benzothiophene (58%). 相似文献