Journal of Synthetic Organic Chemistry, Japan
Online ISSN : 1883-6526
Print ISSN : 0037-9980
ISSN-L : 0037-9980
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Volume 71, Issue 8
Displaying 1-11 of 11 articles from this issue
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Preface
Reviews and Accounts
  • Total Synthesis of Cortistatin A and J
    Shuji Yamashita, Masahiro Hirama
    2013 Volume 71 Issue 8 Pages 768-778
    Published: August 01, 2013
    Released on J-STAGE: September 24, 2013
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.71.768
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    Cortistatins, isolated from Cortisium simplex in 2006, exhibit potent inhibition against the proliferation of human umbilical vein endothelial cells (HUVECs). This paper describes the details of our total synthesis of cortistatins A and J. The key features of our strategy include (1) an efficient Knoevenagel/electrocyclic reactions to couple the diketone and the CD-ring fragment, (2) a chemoselective radical cyclization to construct the oxabicyclo[3.2.1]octane system, (3) a highly stereocontrolled installation of the isoquinoline unit, and (4) a late-stage functionalization of the A-ring.
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  • Synthesis and Properties of π-Conjugated Compounds Based on Carbazole
    Yosuke Nakamura, Shin-ichiro Kato, Hiroto Noguchi
    2013 Volume 71 Issue 8 Pages 779-790
    Published: August 01, 2013
    Released on J-STAGE: September 24, 2013
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.71.779
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    Suitable functionalization of carbazole, namely the combination with other π-electron systems, can modify the π-conjugation behavior, electron-donating ability or fluorescence properties, and then provide various photofunctional materials. Recently, we have synthesized various carbazole-based π-conjugated compounds such as carbazole-based cyclophanes (carbazolophanes), carbazole dimers, carbazole-thiophene dyads and oligomers, and carbazole-fullerene dyads, and studied their properties. This account reviews their synthesis, structures, and properties in detail.
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  • Asymmetric Catalysis Mediated by Optically Active Bis(oxazolinyl)phenyl Metal Complexes
    Jun-ichi Ito, Hisao Nishiyama
    2013 Volume 71 Issue 8 Pages 791-803
    Published: August 01, 2013
    Released on J-STAGE: September 24, 2013
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.71.791
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    Transition metal complexes bearing anionic meridional ligands can construct highly reactive catalyst in homogeneous reactions. In these complexes, a metal-carbon σ-bond and two metallacycles can induce high stability, unique electronic properties and steric environments. This paper describes the development of new optically active metal complexes containing bis(oxazolinyl)phenyl (Phebox) ligands for enantioselective catalytic reactions. The Phebox-Rh complex serves as a highly efficient and multi-functional catalyst for several types of enantioselective transformations including reduction, C-C bond formation and functionalization reactions, such as hydrosilylation, conjugate reduction, reductive aldol reaction, direct aldol or alkynylation reactions, and β-boration. The Phebox-Ru complex was also developed as a selective catalyst in enantioselective reactions for hydrogenation, cyclopropanation, and alkynylation reactions. The Phebox-Fe, Pd and Ir complexes were found to have a variety of reactivity in catalytic and stoichiometric reactions.
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  • Catalytic Borylation and Silylation of Unsaturated Organic Molecules: Reaction Control by Transition Metal Catalysts and Applications to Organic Synthesis
    Toshimichi Ohmura
    2013 Volume 71 Issue 8 Pages 804-817
    Published: August 01, 2013
    Released on J-STAGE: September 24, 2013
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.71.804
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    Transition-metal-catalyzed reactions for introduction of boryl and silyl groups into unsaturated organic molecules are described. Enantioselective silaboration of terminal allenes and silaborative C-C cleavage of meso-methylenecyclopropanes were achieved by a palladium catalyst bearing an optically active phosphorus ligand, (R)-2-bis(3,5-dimethylphenyl)phospino-1,1’-binaphthyl. New silylboronic esters bearing chloro, alkoxy, and dialkylamino groups on the silicon atoms were developed and used for silaboration of alkenes and alkynes. Intramolecular silaboration of alkenes was catalyzed by platinum complexes, in which the cis/trans selectivity of the resulting cyclic silyl ethers could be controlled complementarily by the phosphorus ligands on the platinum. In silaboration of terminal alkynes, complementary control of regio- and stereoselectivities were achieved. Silylboronic esters bearing diethylamino group on the silicon atom reacted as a silylene equivalent in the palladium-catalyzed reaction of terminal alkynes, 1,3-dienes, and 2-alkenylindoles to give silole derivatives. Dearomatizing conversion of pyridines was achieved by a palladium-catalyzed silaboration and a rhodium-catalyzed hydroboration. The boron- and silicon-containing compounds synthesized by the above-mentioned methods were utilized in C-C bond-forming reactions.
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  • Development of Catalytic and Enantioselective Diels-Alder Reaction of Electron-Rich Dienes Using Chiral Rare-Earth Metal Complex
    Shinji Harada, Takahiro Morikawa, Shiharu Hiraoka, Atsushi Nishida
    2013 Volume 71 Issue 8 Pages 818-829
    Published: August 01, 2013
    Released on J-STAGE: September 24, 2013
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.71.818
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    Danishefsky diene (1-methoxy-3-trialkylsiloxy-1,3-butadiene) is known as a reactive and useful substrate for Diels-Alder reaction to give highly functionalized cyclohexenes. However, the diene is so unstable under acidic conditions that applicable Lewis acid to activate dienophile is quite limited. We developed Yb(OTf)3/BINAMIDE or BINUREA/DBU catalyst, which realized the first example of catalytic asymmetric Diels-Alder reaction of Danishefsky diene and electron-deficient olefins. The Diels-Alder reaction of several types of dienophiles with Danishefsky diene was efficiently facilitated by the catalyst to give exclusively exo adducts. The Diels-Alder adduct can be transferred to various synthetic intermediates. Apparent (+)-non-linear effects between asymmetric induction and the enantiomeric composition of BINAMIDE may suggest the possible formation of a reservoir of non-reactive aggregates. A structure of ytterbium salt was discussed.
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  • Structure-Activity Relationship Study and Total Synthesis of Pyripyropene A as a Potent ACAT2-Selective Inhibitor
    Masaki Ohtawa, Satoshi Omura, Hiroshi Tomoda, Tohru Nagamitsu
    2013 Volume 71 Issue 8 Pages 830-843
    Published: August 01, 2013
    Released on J-STAGE: September 24, 2013
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.71.830
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    Fungal pyripyropene A (PPPA, 1), consisting of pyridine, α-pyrone, and sesquiterpene moieties, is the only potent and selective inhibitor of acyl-CoA: cholesterol acyl transferase 2 (ACAT2) isozyme. In an effort to develop potent and selective inhibitors toward ACAT2, structure-activity relationship studies were carried out using derivatives based on 1. We have successfully developed novel 1,11-O-o-substituted benzylidene-7-p-cyanobenzoyloxy PPPA derivatives that exhibit significantly more potent ACAT2 inhibitory activity and much higher isozyme selectivity than 1.
    Furthermore, we have achieved a stereocontrolled total synthesis of 1. Key features of the synthetic strategy included an intramolecular Ti(III)-mediated radical cyclization for construction of the A-ring, stereoselective β-epoxide formation/Peterson olefination for preparation of the functional groups on the B-ring, and stereoselective intramolecular cyclization through hetero-Michael addition for C-ring formation. Extension of this chemistry to the synthesis of an A-ring truncated PPPA analog for structure-activity relationship studies has also been achieved.
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