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1.
Total Synthesis and Structure Elucidation of JBIR‐39: A Linear Hexapeptide Possessing Piperazic Acid and γ‐Hydroxypiperazic Acid Residues 下载免费PDF全文
Dr. Masahito Yoshida Naoki Sekioka Dr. Miho Izumikawa Dr. Ikuko Kozone Dr. Motoki Takagi Dr. Kazuo Shin‐ya Prof. Dr. Takayuki Doi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):3031-3041
The total synthesis and stereochemical structural elucidation of JBIR‐39, containing four nonproteinogenic piperazic acid (Piz) residues, is reported. The synthesis includes Sc(OTf)3‐catalyzed acylation of a Piz(γ‐OTBS) derivative with piperazic acid chloride, providing the desired Piz‐Piz(γ‐OTBS) dipeptide in high yield without epimerization. After assembling two additional Piz moieties and (S)‐isoleucic acid at the N‐terminus, amidation with the (R)‐α‐methylserine ester at the C‐terminus, and deprotection afforded the desired (2R,8S)‐hexapeptide, which is the assumed structure of JBIR‐39. Although the spectral data of the (2R,8S)‐hexapeptide was not identical to JBIR‐39, further synthesis of three stereoisomers confirmed the stereochemical structure of JBIR‐39 to be (2S,6S,8S,11R,16S,21R,26S,27S). 相似文献
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Hiroyuki Nishide Naoki Yoshioka Yukoh Saitoh Ritsuko Gotoh Takeshi Miyakawa Eishun Tsuchida 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):775-786
Abstract m- and p Bis(diphenylene)propenylphenylacetylene (m-, p-8) were synthesized and polymerized with WCI6, MoCl5, and Rh catalyst, yielding solvent-soluble poly(phenylacetylene)s bearing a π-conjugated bis(di-phenylene)propenyl groups (m-, p-7a). The polymers gave their polyanion derivatives, which were electrolytically and chemically oxidized to yield the corresponding polyradicals (m-, p-7b). The polyradicals were chemically very stable due to the resonance stabilization of an unpaired electron whose spin concentration could be increased up to ca. 2 × 1023 spins per molar monomer unit. ESR spectroscopy suggested an antiferro-magnetic interaction between unpaired electrons. 相似文献
4.
Shigeo Iwayanagi Ikuko Sakurai Tosio Sakurai Tsuneo Seto 《Journal of Macromolecular Science: Physics》2013,52(2):163-177
The crystal structure of trans-1,4-polybutadiene has been reported by Natta et al. to be pseudo-hexagonal below its solid-phase transition temperature. In the present X-ray structure analysis, it is revealed that the crystal belongs to the monoclinic system with the space group P21/a. The unit cell, with the lattice constants a = 8.63 Å, b = 9.11 Å, c = 4.83 Å, and β = 114°, includes four molecular segments. 相似文献
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The size of support of initial heat distribution is determined by the heat flow observed either at any fixed time or at any fixed position 相似文献
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Akihiko Ishii Masashi Saitoh Tetsuhiko Kawai Masami Murata Juzo Nakayama 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8-9):2025-2026
The reaction of isolable dithiirane 1-oxides with (Ph 3 P) 2 Pt( m 2 -C 2 H 4 ) provided the title complexes in high yields. 31 P NMR spectroscopy of the phosphine ligands of the complexes and x-ray crystallographic analysis of a complex were reported. 相似文献
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Mohamad Kamarol Mohd Jamil Shinya Ohtsuka Masayuki Hikita Hitoshi Saitoh Masayuki Sakaki 《Journal of Electrostatics》2011,69(6):611-617
This paper presents the decomposition by-products of trifluro-iodo-methane and their relative proportions in the gas phase under the occurrence of partial discharge. The experiment was performed in the presence of water vapor from 250 to 400 ppm under a non-uniform electric field configuration. The experimental results reveal that the by-products of C2F6, C2F4, C2F5I with the amount of 1300, 200, and 55 (CH3I) ppm, respectively, were produced for a cumulative charge of 161 mC. Other by-products, such as C3F8, CHF3, C3F6 CH3I were obtained at less than 30 ppm C2F6 was the dominant gas by-product of trifluro-iodo-methane suffering partial discharge. 相似文献
10.
Tsuyoshi Satoh Yu AwataYuichi Kato Shingo OgataMasashi Ishigaki Shimpei SugiyamaHideki Saitoh 《Tetrahedron》2011,67(6):1102-1113
Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were derived from cyclobutanones and chloromethyl p-tolyl sulfoxide, with lithium enolate of tert-butyl carboxylates, amides, lithium α-sulfonyl carbanions, and lithium α-carbanion of acetonitrile gave adducts in high to quantitative yields. The adducts were treated with Grignard regents, such as i-PrMgCl and EtMgCl in toluene to afford 1-substituted cyclopentenes in good to high yields with one-carbon ring-expansion via 1,2-carbon-carbon (1,2-CC) insertion reaction of the generated magnesium carbenoid intermediates. The magnesium carbenoid 1,2-CC insertion was found to be highly stereospecific. When optically pure chloromethyl p-tolyl sulfoxide was used in this procedure, optically active 1-substituted cyclopentenes were obtained in high optical purity. 相似文献