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81.
Takeshi Yamada Yuki MizutaniYoshihide Umebayashi Naoko InnoMaiko Kawashima Takashi KikuchiReiko Tanaka 《Tetrahedron letters》2014
Tandyukisin (1), a novel decalin derivative with an enolic β-ketoaldehyde, has been isolated from a strain of Trichoderma harzianum OUPS-111D-4 originally derived from the marine sponge Halichondria okadai, and its structure has been elucidated on the basis of spectroscopic analyses using 1D and 2D NMR techniques. In addition, the absolute configuration for 1 was established by the application of CD spectrum to the tribenzoate derivative. This compounds exhibited moderate cytotoxicity against human cancer cell lines. 相似文献
82.
Neomacrophorins I (1), II (2), and III (3) were isolated from the culture broth of Trichoderma sp. 1212-03, which was collected at Shirakami Mountainous area in Japan. Structural analyses disclosed that these resemble known macrophorins but possess axial-hydroxy group at C3 as well as different side chains at C7′. These are diastereomeric forms of macrophorins for 5′,6′-epoxide functionality. The NMR analyses suggested their relative configurational relationship between the C1–C15 drimene and C1′–C7′ epoxyquinone moieties. ECD spectral discussions verified them particularly for C5′,C6′-epoxyquinone (1), C5′,C6′-epoxysemiquinone (2 and 3), and 2″,3″-dihydroxybutanoate moiety in 1 and 2. The configuration of C3″-stereocenter of 3 was determined by chiral GC–MS after converting into methyl (S)-3″-hydroxybutanoate by basic of 3 methanolysis. Biological assays disclosed that 1 induces hyphal branching of Cochliobolus miyabeanus as well as cytotoxicity against human colorectal cancer COLO 201. 相似文献
83.
Naokazu Kano Hideaki Miyake Keishi Sasaki Takayuki Kawashima 《Heteroatom Chemistry》2015,26(2):183-186
The Si Si bond of a pentacoordinated disilicate was readily cleaved by treatment with 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone in the presence of sodium carbonate under mild conditions. The bond cleavage did not proceed under the same conditions after conversion of the disilicate into the corresponding monoanionic silylsilicate and neutral disilane by protonation. The difference in the charges of the Si Si bond compounds affects the reactivity toward an oxidant, resulting in the Si Si bond cleavage, considering that all of these compounds have a bond between pentacoordinated silicon atoms. 相似文献
84.
85.
Robust Inclusion Complexes of Crown Ether Fused Tetrathiafulvalenes with Li+@C60 to Afford Efficient Photodriven Charge Separation 下载免费PDF全文
Dr. Mustafa Supur Yuki Kawashima Dr. Karina R. Larsen Dr. Kei Ohkubo Prof. Jan O. Jeppesen Prof. Shunichi Fukuzumi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):13976-13983
Inclusion complexes of benzo‐ and dithiabenzo‐crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li+@C60 ( 1? Li+@C60 and 2? Li+@C60). The strong complexation has been quantified by high binding constants that exceed 106 M ?1 obtained by UV/Vis titrations in benzonitrile (PhCN) at room temperature. On the basis of DFT studies at the B3LYP/6‐311G(d,p) level, the orbital interactions between the crown ether moieties and the π surface of the fullerene together with the endohedral Li+ have a crucial role in robust complex formation. Interestingly, complexation of Li+@C60 with crown ethers accelerates the intersystem crossing upon photoexcitation of the complex, thereby yielding 3(Li+@C60)*, when no charge separation by means of 1Li+@C60* occurs. Photoinduced charge separation by means of 3Li+@C60* with lifetimes of 135 and 120 μs for 1? Li+@C60 and 2? Li+@C60, respectively, and quantum yields of 0.82 in PhCN have been observed by utilizing time‐resolved transient absorption spectroscopy and then confirmed by electron paramagnetic resonance measurements at 4 K. The difference in crown ether structures affects the binding constant and the rates of photoinduced electron‐transfer events in the corresponding complex. 相似文献
86.
We investigated the fluorescent properties, including the excited-state intermolecular proton transfer, of urea derivatives comprising a coumarin ring, which is a widely used fluorophore. We prepared two different coumarin–urea derivatives, 6CU and 7CU, which bear a urea-based substituent at the 6 and 7 positions of a coumarin ring, respectively. In the presence of the acetate ion, 7CU showed additional tautomer fluorescence emission with respect to 6CU, indicating that tautomer formation depends on the positions of the urea-based substituent on the coumarin ring. Thus, the resonance structures of urea derivatives might play an important role in the behavior of dual fluorescence, which is an important phenomenon applicable to photochemical anion sensing. Moreover, in order to further improve the fluorescence properties of the mentioned derivatives, a CF3 group was introduced in a phenyl ring opposite to a coumarin ring. The fluorescence quantum yield of 7CUCF3 thus synthesized was 65 times as large as that of 7CU, an observation that renders 7CUCF3 a suitable anion sensor candidate. The results of this study will contribute to the development of new molecular designs for highly fluorescent sensing. 相似文献
87.
Yasuo Horikawa Takeshi Takeda Toshiki Takizawa Taro Akazawa Ryota Fujio Tatsuo Fujimaki 《Journal of polymer science. Part A, Polymer chemistry》1996,34(7):1183-1188
The anionic polymerization of 1,3-butadiene using a novel metalloidal anion initiator, triallylstannyllithium (TALi)-allyllithium (ALi), was studied. The TALi-ALi initiated anionic polymerization of 1,3-butadiene gave the star polymer along with the linear polybutadiene (PBD). The star polymer consisted of three PBD branches and a central tin atom. What is striking is a fact that the number-average molecular weights (Mn) and molecular weight distribution of three PBD branches and linear PBD were almost identical. A reversible chain transfer polymerization mechanism, which includes the equilibrium between tri(macroallyl)-stannyllithium and macroallylic anion, is proposed. © 1996 John Wiley & Sons, Inc. 相似文献
88.
89.
J. Kawanaka Y. Takeuchi A. Yoshida S. J. Pearce R. Yasuhara T. Kawashima H. Kan 《Laser Physics》2010,20(5):1079-1084
A MOPA laser system for high pulse energy and high average power has been developed by using a cryogenic Yb:YAG. In the regenerative
amplifier with our original TRAM architecture, the high pulse energies of 6.5 and 1.5 mJ were obtained at the repetition rate
of 200 Hz and 1 kHz, respectively. An optical efficiency was as high as ηo-o = 9.3% with an excellent beam quality of M
2 < 1.1, which ensured that a cryogenic Yb:YAG TRAM had a high thermal strength. The following four pass power amplifier with
a cryogenic Yb:YAG rod showed 140 mJ at 100 Hz. Both a high optical efficiency of ηo-o = 30% and a high slope efficiency of ηs = 44% showed that an efficient laser operation could be realized for a power amplification with both a high pulse energy
and a high average power by using a cryogenic Yb:YAG. 相似文献
90.
Yoshitomo Ono Naoyuki Kawashima Hiroto Kudo Tadatomi Nishikubo Takabumi Nagai 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4412-4421
The ring‐opening copolymerization of donor–acceptor norbornadiene (D–A NBD) dicarboxylic acid monoglycidyl ester derivatives with D–A NBD dicarboxylic acid anhydride was performed with tetraphenylphosphonium bromide as a catalyst in toluene to produce new norbornadiene (NBD) polyesters containing D–A NBD moieties in the main chain and in the side chain in one step in good yields. The photoisomerization of the D–A NBD moieties in these polyesters proceeded very smoothly to give the corresponding quadricyclane groups. Because these NBD polyesters contained many NBD moieties in the polymer chain, they had the highest capacity for heat storage in the D–A NBD polymers reported so far. The stored thermal energy of the irradiated polyesters was evaluated by differential scanning calorimetry analysis to be approximately 150–190 J/g. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4412–4421, 2005 相似文献