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41.
Prof. Dr. Hiroshi Tanaka Ryota Takeuchi Prof. Dr. Mitsuru Jimbo Nami Kuniya Prof. Dr. Takashi Takahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(9):3177-3187
The synthesis and biological evaluation of the Forssman antigen pentasaccharide and derivatives thereof by using a one‐pot glycosylation and polymer‐assisted deprotection is described. The Forssman antigen pentasaccharide, composed of GalNAcα(1,3)GalNAcβ(1,3)Galα(1,4)Galβ(1,4)Glc, was recently identified as a ligand of the lectin SLL‐2 isolated from an octocoral Sinularia lochmodes. The chemo‐ and α‐selective glycosylation of a thiogalactoside with a hemiacetal donor by using a mixture of Tf2O, TTBP and Ph2SO, followed by activation of the remaining thioglycoside, provided the trisaccharide at the reducing end in a one‐pot procedure. The pentasaccharide was prepared by the α‐selective glycosylation of the N‐Troc‐protected (Troc=2,2,2‐trichloroethoxycarbonyl) thioglycoside with a 2‐azide‐1‐hydroxyl glycosyl donor, followed by glycosidation of the resulting disaccharide at the C3 hydroxyl group of the trisaccharide acceptor in a one‐pot process. We next applied the one‐pot glycosylation method to the synthesis of pentasaccharides in which the galactosamine units were partially and fully replaced by galactose units. Among the three possible pentasaccharides, Galα(1,3)GalNAc and Galα(1,3)Gal derivatives were successfully prepared by the established method. An assay of the binding of the synthetic oligosaccharides to a fluorescent‐labeled SLL‐2 revealed that the NHAc substituents and the length of the oligosaccharide chain were both important for the binding of the oligosaccharide to SLL‐2. The inhibition effect of the oligosaccharide relative to the morphological changes of Symbiodinium by SLL‐2, was comparable to their binding affinity to SLL‐2. In addition, we fortuitously found that the synthetic Forssman antigen pentasaccharide directly promotes a morphological change in Symbiodinium. These results strongly indicate that the Forssman antigen also functions as a chemical mediator of Symbiodinium. 相似文献
42.
Dr. Ryu Yamasaki Dr. Masato Ohashi Kyotaro Maeda Takuya Kitamura Minami Nakagawa Korehito Kato Tetsushi Fujita Ryohei Kamura Kazuto Kinoshita Dr. Hyuma Masu Prof. Dr. Isao Azumaya Prof. Dr. Sensuke Ogoshi Prof. Dr. Shinichi Saito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3415-3425
A detailed study of the Ni‐catalyzed [4+3+2] cycloaddition reaction between ethyl cyclopropylideneacetate and dienynes has been conducted, resulting in the development of a new method for the synthesis of compounds containing nine‐membered rings. We studied the reactivity of various dienynes, together with their substituent and conformational effects. The mechanism of the reaction was probed by examining the stoichiometric reactions of the Ni complexes and dienynes. 相似文献
43.
Jun Yamamoto Nami Maeda Chiaki Komiya Tomohiro Tanaka Masaya Denda Koji Ebisuno Wataru Nomura Hirokazu Tamamura Youichi Sato Aiko Yamauchi Akira Shigenaga Akira Otaka 《Tetrahedron》2014
A fluoride-responsive (FR) amino acid that induces amide bond cleavage upon the addition of a fluoride was developed, and it was applied to an FR traceable linker. By the use of an alkyne-containing peptide as a model of an alkynylated target protein of a bioactive compound, introduction of the FR traceable linker onto the peptide was achieved. Subsequent fluoride-induced cleavage of the linker followed by labeling of the released peptide derivative was also conducted to examine the potential applicability of the FR traceable linker to the enrichment and labeling of alkynylated target molecules. 相似文献
44.
Hideyasu China Nami Kageyama Hotaka Yatabe Naoko Takenaga Toshifumi Dohi 《Molecules (Basel, Switzerland)》2021,26(7)
We report a convenient and practical method for the preparation of nonexplosive cyclic hypervalent iodine(III) oxidants as efficient organocatalysts and reagents for various reactions using Oxone® in aqueous solution under mild conditions at room temperature. The thus obtained 2-iodosobenzoic acids (IBAs) could be used as precursors of other cyclic organoiodine(III) derivatives by the solvolytic derivatization of the hydroxy group under mild conditions of 80 °C or lower temperature. These sequential procedures are highly reliable to selectively afford cyclic hypervalent iodine compounds in excellent yields without contamination by hazardous pentavalent iodine(III) compound. 相似文献
45.
Dr. Masato Ohashi Ryohei Doi Prof. Dr. Sensuke Ogoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):2040-2048
This report describes the first Pd0‐catalyzed cross‐coupling of hexafluorobenzene (C6F6) with diarylzinc compounds to give a variety of pentafluorophenyl arenes. This reaction could be applied to other perfluoroarenes, such as octafluorotoluene, pentafluoropyridine, and perfluoronaphthalene, to give the corresponding polyfluorinated coupling products. The optimal ligand in this catalytic reaction was PCy3, and lithium iodide was indispensable as an additive for the coupling reaction. One of the roles of lithium iodide in this catalytic reaction was to promote the oxidative addition of one C?F bond of C6F6 to palladium. Stoichiometric reactions revealed that an expected oxidative‐addition product, trans‐[Pd(C6F5)I(PCy3)2], generated from the reaction of [Pd(PCy3)2] with C6F6 in the presence of lithium iodide, was not involved in the catalytic cycle. Instead, a transient three‐coordinate, monophosphine‐ligated species, [Pd(C6F5)I(PCy3)], emerged as a potential intermediate in the catalytic cycle. Therefore, we isolated a novel PdII complex, [Pd(C6F5)I(PCy3)(py)], in which pyridine (py) acted as a labile ligand to generate the transient species. In fact, in the presence of lithium iodide, this PdII complex was found to react smoothly with diphenylzinc to give the desired pentafluorophenyl benzene, whereas the same reaction conducted in the absence of lithium iodide resulted in a decreased yield of pentafluorophenyl benzene, which indicated that the other role of lithium iodide was to enhance the reactivity of the organozinc species during the transmetalation step. 相似文献
46.
Seyyedeh Fatemeh Mousavi Zinatossadat Hossaini Faramarz Rostami-Charati Navabeh Nami 《Journal of heterocyclic chemistry》2020,57(11):3868-3881
In this research, synthesis of pyrrolo isoquinoline derivatives in excellent yields was performed using the multicomponent reaction of isoquinoline, alkyl bromides, 2-hydroxyacetophenone, or its derivatives, dimethyl carbonate as a green reagent and KF/clinoptinolite nanoparticles as a catalyst in the aqueous media at 80°C. The Punica granatum peel water extract was used as the green media for the synthesis of PG-KF/clinoptilolite nanoparticles in high yield. The PG-KF/clinoptilolite nanoparticles show a significant basic catalytic role in these reactions in preparing the product in high yield and used for several times. In addition, for studying the antioxidant ability of some of the synthesized compounds, diphenyl-picrylhydrazine (DPPH) radical trapping and power of ferric reduction tests are employed. The short time of the reaction, high yields of the product, easy separation of the catalyst and products are some of the advantages of this procedure. 相似文献
47.
48.
Y. Ohashi Y. Kurita T. Suzuki M. Tokuda 《Journal of the mechanics and physics of solids》1981,29(1):51-67
Ilyushin's general plasticity theory expressed in a vector space corresponding to the deviatoric tensor space is available in formulating precise stress-strain relations of inelastic deformations by incorporating the deformation history of metals under complex loadings. In this case, the hypothesis of local determinability proposed by Lensky (1960) is useful for determining the explicit form of the stress-strain relation. In the present paper, the hypothesis is discussed by using not only data obtained by an experiment in which the history effect on the succeeding deformation is clearly estimated, but also data described in previous work. As the result, the hypothesis of local determinability has been confirmed to hold with high accuracy in every case. 相似文献
49.
The electron impact induced fragmentation of 1-benzoylbenzotriazole has been studied by 13C labelling experiments. It has been found that the loss of CO from the [M ? N2]+˙ ions proceeds by two routes; about 78% of the ions decompose via the molecular ions of the corresponding thermal fragmentation product, 2-phenylbenzoxazole, and 22% via those of the corresponding photochemical fragmentation product, 6-phenanthridone. 相似文献
50.
The HF dimer is believed to exhibit an internal rotation tunneling process between two planar but nonlinear equilibrium configurations, during which tunneling the roles of the hydrogen-bonded and the free hydrogen atom are interchanged. This process can be represented schematically with labeled atoms as HlFaH2Fb ? FaHlFbH2, and gives rise to a permutation-inversion group G4 containing four operations. In the present work the vibration-rotation-tunneling problem in (HF)2 is treated group theoretically in three ways: (i) by allowing tunneling only through a trans planar C2h intermediate, (ii) by allowing tunneling only through a cis planar C2v intermediate, and (iii) by considering the trans and cis tunneling processes both to occur, though not necessarily with the same probability. The molecular symmetry groups used for these treatments are (i) the point group C2h, (ii) the point group C2v, and (iii) a double group, which might be thought of as . Nonplanar tunneling paths are not considered, since the internal axis method (IAM) coordinate system used here cannot easily be adapted to nonplanar internal rotation motions in this molecule. Various-details of energy level diagrams, symmetry species for operators, selection rules for spectroscopic transitions, and statistical weights are presented for the (HF)2 tunneling problem, as well as some speculation on the general question of when point groups, permutation-inversion groups, or double groups are preferable for treating large-amplitude vibrational motion problems. 相似文献