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Volume 66, Issue 9
Displaying 1-8 of 8 articles from this issue
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Masato Oikawa, Makoto Sasaki2008 Volume 66 Issue 9 Pages 836-845
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSAzaspiracids (AZAs) are a group of shellfish toxin responsible for the poisoning called "azaspiracid poisoning (AZP)" prevailed in a coastal region of north Europe to northwest Africa since 1995. To establish the molecular basis including its chemical structure and its mode of biological action, several synthetic studies have been developed on azaspiracid-1 (AZA-1). In this review, studies on the syntheses of the FGHI- and EFGHI-ring domains corresponding to a lower half of AZA-1, reported by groups of Forsyth, Evans, Nicolaou, and us, are summarized. Retrosynthetic analysis, fragment synthesis and their assembly, and stereoselective construction of the unique spiroaminal HI-ring domain are main topics of this review. Furthermore, total syntheses successfully made by Evans and Nicolaou groups are described.View full abstractDownload PDF (5937K) -
Shinya Oishi, Tetsuo Narumi, Hiroaki Ohno, Akira Otaka, Nobutaka Fujii2008 Volume 66 Issue 9 Pages 846-857
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSPeptide bonds are one of the essential contributors to overall structure and functions of bioactive peptides. The partial double-bond character derived from the resonance structure restricts the free rotation of the carbon-nitrogen bond and stabilizes the planar conformations. Additionally, the ability to form hydrogen bonds allows the stabilization of characteristic secondary structures such as α-helix and β-turn as well as the association with the receptors. Alkene dipeptide isosteres, based on the concept of ω-dihedral angle planarity, have been used as amide bond equivalents, which serve as mechanistic probes lacking amide polarity. We have developed a facile methodology for the stereoselective synthesis of highly functional dipeptide isosteres. The key reaction is the alkylation of δ-aminated α, β-enoates having an appropriate leaving group at the γ-position. Organocopper-mediated anti-SN2' alkylation of α, β-enoates afforded multi-substituted olefin-containing isosteres. One-pot reduction-transmetalation-alkylation of γ, γ-difluoro-α, β-enoates provided fluoroalkene dipeptide isosteres. Reduction of these substrates with organocuprate, SmI2, or Pd/PhSiH3/Et3N system gave Xaa-Gly-type mimetics. Similar methods were also utilized for the preparation of cis-peptide bond mimetics. The resulting isosteres and the key intermediates were studied in structure-activity relationship of bioactive peptides including integrin αvβ3 antagonist, chemokine receptor CXCR 4 antagonist, puberty-related GPR 54 agonist, and peptide transporter PEPT1 substrate.View full abstractDownload PDF (5502K) -
Atsushi Wakamiya, Shigehiro Yamaguchi2008 Volume 66 Issue 9 Pages 858-868
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSUtilization of boron, a group 13 element, as a key element for developing new functional electronic and optoelectronic materials is an important direction in the organoboron chemistry. Boron has several characteristic features, such as trigonal planar geometry for trivalent boron compounds, high Lewis acidity, and effective orbital interaction with π-conjugated frameworks through the vacant p-orbital (i.e., ρπ-π* conjugation). Exploiting these features of the boron element for molecular designs allows us to create sophisticated π-electron materials having attractive photophysical and electronic properties. We here present some progress in our chemistry, including B, B', B"-trianthrylborazine (B3N3)-based molecular bundles, boryl-substituted thienylthiazole π-electron systems with intramolecular B-N coordination, borole- and dibenzoborole-based π-conjugated compounds, and boryl-substituted emissive organic solids.View full abstractDownload PDF (10623K) -
Kenji Ogino, Hisaya Sato2008 Volume 66 Issue 9 Pages 869-879
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThis article describes the synthesis of hole transporting polymers containing triphenylamine (TPA) unit either in side chain or main chain for electroluminescent devices, and photorefractive applications. Radically polymerized polyacrylate having tetraphenyldiaminobiphenyl (TPD) unit showed higher drift mobility compared with conventional poly(N-vinylcarbozole) (PVK). TPA derivatives were reacted with paraformaldehyde or benzaldehyde in the presence of p-toluenesulfonic acid to yield polymers soluble in common organic solvents. Acid catalyzed Friedel-Crafts reactions between TPA derivatives and divinylbenzene were also applied to prepare the main chain polymers. TPA derivatives were oxidatively coupled to afford polymers with well-defined structure. Resulting polymer sensitized with fullerene showed much higher photoconductivity than PVK. Electron transporting polymers having oxadiazole, fluorene, or thioxanthene unit are also introduced. For the further improvement of device performance, molecular design for multifunctional and multiphased materials including block copolymers and rod-coil type polymers is described.View full abstractDownload PDF (7491K) -
Kiyoshi Ikeda, Masayuki Sato2008 Volume 66 Issue 9 Pages 880-892
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSSialic acids are involved in a number of biological processes including cell-to-cell, cell-to-microorganism, -toxin, and -antibody binding. Among the diverse arrays of compounds related to sialic acid family, 2-deoxy-2, 3-didehydro-N-acetylneuraminic acids (Neu 5Ac2en) have been known as an inhibitor of sialidase, a key enzyme responsible for propagation of the influenza virus, occupying its important position in the modern medicinal chemistry. Human parainfluenza virus type 1 (hPIV-1) is a serious human pathogen causing upper and lower respiratory disease and is known to be a cause of croup in infants and young children. This article reviews our progress of the synthesis of Neu5Ac2en analogs and their biological evaluations against hPIV-1 sialidase.View full abstractDownload PDF (4104K) -
Ryo Okamoto, Yasuhiro Kajihara2008 Volume 66 Issue 9 Pages 893-905
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThis paper describes for the semisynthesis of diverse asparagine-linked oligosaccharides (Asn-oligosaccharides) from asparagine-linked biantennary complex-type-disialylundecasaccharide obtained from egg yolk. This semisynthesis employs chemical modification and branch specific exo-glycosidase digestion (β-D-galactosidase, N-acetyl-β-D-glucosaminidase and α-ll-mannosidase). Efficient semisynthesis has enabled us to prepare appropriate amount of asparagine linked oligosaccharide and to examine solid phase synthesis for several glycopeptides having homogeneous and intact oligosaccharides. This solid phase glycopeptides synthesis has also been examined to develop for the preparation of glycoprotein. The synthetic target was to be glycoprotein, monocite chemotactic protein-3 (MCP-3). This glycoprotein has a complex type disialylundecasaccharide and two disuflide bond. This chemical synthesis employed solid phase synthesis, native chemical ligation and protein folding protocol to obtain desired homogeneous glycoprotein. The disufide map, CD measurement and enzyme linked immuno sorbent assay (ELISA) supported that glycoprotein exhibited that the desired three dimentional structure.View full abstractDownload PDF (5366K) -
Shintaro Ishida2008 Volume 66 Issue 9 Pages 906-907
Published: September 01, 2008
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSIn this short review, a new methodology of preparation of the silacyclic compounds using silylene and their application for organic synthesis are described. Silylene transfer from silacyclopropane to alkene, alkyne, imine, and α, β-unsaturated carbonyl compounds was catalyzed by silver salt to give the corresponding [1+2] or [1+4] cycloadducts in good yields. Combination of the cycloaddition, Ireland-Claisen rearrangement, and oxidative cleavage of silicon-carbon bond provided the regio-and stereoselective synthesis of polyol and α-hydroxyacid in a mild condition.View full abstractDownload PDF (1777K) -
2008 Volume 66 Issue 9 Pages 908
Published: September 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (219K)
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