Journal of Synthetic Organic Chemistry, Japan
Online ISSN : 1883-6526
Print ISSN : 0037-9980
ISSN-L : 0037-9980
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Volume 73, Issue 6
Displaying 1-10 of 10 articles from this issue
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Preface
Reviews and Accounts
  • Synthesis and Functionalization of Polysaccharide Analogues and Their Application to High-Contrast Tumor Imaging
    Koji Miki
    2015 Volume 73 Issue 6 Pages 580-594
    Published: June 01, 2015
    Released on J-STAGE: July 22, 2015
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.73.580
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    Polymeric self-assemblies and their related aggregates have received great attention because of their huge potential to be used as tumor imaging agents. Amphiphilic polymers consisting of hydrophobic, hydrophilic, and dye segments have been widely accepted as appropriate components of polymeric self-assemblies for tumor imaging, because nanometer-size particles can be accumulated in tumor tissues by the enhanced permeability and retention effect. However, there still exists a problem with selective accumulation of the imaging probe in the target tissue. Recently, we found out the facile synthesis of biocompatible polysaccharide analogues through ring-opening metathesis polymerization of norbornadienes or 7-oxanorbornenes and dihydroxylation, and investigated the functionalization of polysaccharide analogues to be applied as high-performance contrast agents. In this account, polymeric self-assemblies consisting of highly functionalized polysaccharide analogues as contrast agents for optical and photoacoustic tumor imaging are summarized.
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  • Development of Novel and Characteristic Biologically-active Molecules Based on Natural Products: Synthesis and Biological Functions of Cage-shaped Structure of Physalins
    Go Hirai
    2015 Volume 73 Issue 6 Pages 595-606
    Published: June 01, 2015
    Released on J-STAGE: July 22, 2015
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.73.595
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    We have focused on the design and creation of new biologically active molecules based on natural products or biomolecules. This article summarizes our synthetic approach towards the clarification of the mode-of-action of physalins, which are complex oxygenated steroidal natural products. Physalins consist of the typical plant-steroidal structure displayed in the AB-ring and the unique cage-shaped DEFGH-ring system present on the right side of the structures. As other plants steroids such as withanolides possess a similar AB-ring structure and sometimes exhibit similar biological activities, the AB-ring structure was considered to be relevant for their biological functions. We synthesized physalin analogues without the AB-ring structure in order to clarify the contribution of the right-side cage-shaped structure for the biological effect in physalins. Biological investigations using the synthesized analogues along with the natural products revealed that, among the analogues, PBright-4 showed moderate inhibitory activity towards NF-κB transcriptional activation, through a similar mode-of-action with physalin B, which possesses a double bond at the C5-C6 position. These results clearly indicated that the right-side partial structure of physalins plays a significant role in their biological activity.
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  • Total Synthesis of Polygalolide A by Intramolecular C-Glycosylation
    Masaatsu Adachi
    2015 Volume 73 Issue 6 Pages 607-615
    Published: June 01, 2015
    Released on J-STAGE: July 22, 2015
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.73.607
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    Total synyhesis of polygalolide A, a secondary metabolite isolated from a Chinese medicinal plant, was achieved. In order to construct an oxabicyclo[3.2.1] core skeleton, we have developed an intramolecular Ferrier-type C-glycosylation of a glucal modified with siloxyfuran as an internal nucleophile. Although the conditions found in the model experiments did not undergo the C-glycosylation, further examination led us to find that combination of TMSOTf and 2,4,6-collidine was the best condition, giving oxabicyclo[3.2.1]octene with correct quaternary stereogenic centers in high yield. The successful production of the single diastereomer indicated that the siloxy group at the C-3 position played a crucial role for the stereocontrol. After transformation into tetracyclic intermediate, a phenolic moiety was finally introduced by Mukaiyama aldol reaction to furnish polygalolide A.
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  • Markovnikov-Selective Hydrometallation Catalyzed by Mono (phosphine) palladium (0) Complexes: Synthesis and Reactivity of Heterodinuclear Hydridopalladium Intermediate
    Nobuyuki Komine, Masafumi Hirano, Sanshiro Komiya
    2015 Volume 73 Issue 6 Pages 616-631
    Published: June 01, 2015
    Released on J-STAGE: July 22, 2015
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.73.616
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    Syntheses of the heterodinuclear hydride complexes and their applications to catalytic hydrometallation reactions are described. Series of heterodinuclear palladium and platinum hydride complexes, L'2HPdMLn and L'2HPtMLn [L'=1/2 dppe, PMe3, PEt3, P(CH2Ph)3, PMe2Ph, PMePh2, PPh3, PCy3; MLn=MoCp(CO)3, WCp(CO)3, Mn(CO)5] are prepared by (i) the metathetical reaction of a mononuclear (halogeno)(hydrido)metal complex with an ate complex, (ii) the β-hydride elimination from the heterodinuclear ethyl complex, and (iii) the oxidative addition of a mononuclear hydride complex to a zerovalent metal complex. The reactions of L'2HPtMLn with electron-deficient alkenes lead to the reductive elimination to give the corresponding alkene complex of Pt(0) and MHLn. However, the similar treatment of L'2HPdMLn with electron-deficient alkenes gives the corresponding mononuclear alkyl complex MRLn. Mono(phosphine)palladium(0) complexes, Pd(diallyl ether)L' (L'=PPh3, PCy3, PMe3, PEt3) are found to be efficient active catalysts for the hydrometallation of electron-deficient alkenes of unreactive Mo, W, and Mn hydrides, MoHCp(CO)3, WHCp(CO)3, and MnH(CO)5. Scope and reaction mechanisms of the hydrometallation are described. This reaction involves a heterodinuclear hydridopalladium complex, L'HPdMLn as an active intermediate. An application of this catalysis to hydrosilylation of electron-deficient alkenes is also described.
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  • Copper-Catalyzed Metallation Reactions of Unsaturated Carbon-Carbon Bonds
    Hiroto Yoshida
    2015 Volume 73 Issue 6 Pages 632-648
    Published: June 01, 2015
    Released on J-STAGE: July 22, 2015
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.73.632
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    A copper complex has proven to be an excellent catalyst for diborylation of alkynes and arynes. Under the copper catalysis, the reaction using propargyl ethers affords tri- or tetraborylation products, in which the C-O bonds as well as the C-C triple bonds are borylated all in one pot. A key intermediate of the reaction, a β-borylalkenylcopper species, has been also found to be captured by a tin or a carbon electrophile, leading to three-component borylstannylation or carboboration. Regioselective installation of a boryl moiety into an internal carbon of terminal alkynes has been achieved by use of a masked diboron as a boron source in hydroboration and borylstannylation. In addition, a copper complex has been demonstrated to efficiently catalyze distannylation, hydrostannylation and silylstannylation. Total synthesis of biologically active molecules based on the metallation reactions has also been reported.
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