Journal of Synthetic Organic Chemistry, Japan
Online ISSN : 1883-6526
Print ISSN : 0037-9980
ISSN-L : 0037-9980
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Volume 70, Issue 2
Displaying 1-10 of 10 articles from this issue
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Preface
Reviews and Accounts
  • Organic Synthesis Catalyzed by Plant Enzyme Hydroxynitrile Lyase
    Ken-ichi Fuhshuku, Yasuhisa Asano
    2012 Volume 70 Issue 2 Pages 102-112
    Published: February 01, 2012
    Released on J-STAGE: February 27, 2012
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.70.102
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    Hydroxynitrile lyase (HNL) is a key enzyme in the catabolism of cyanogenic glycosides in higher plants. HNL catalyzes the decomposition of cyanohydrins into corresponding aldehydes or ketones and HCN for defense against predators and microorganisms. The reverse reaction, synthesis of optically active cyanohydrins, has attracted the attention of scientists and industry.
    We discovered several novel sources of HNL among 163 plant species in 74 families examined, using a simple HPLC-based method to determine the activity and stereoselectivity of HNLs. S-selective HNL (S-HNL) activity was found in a homogenate of the leaves of Baliospermum montanum, while R-selective HNLs (R-HNLs) were detected in the leaves and seeds of Passiflora edulis, and the seeds of Eriobotrya japonica, Prunus mume, Prunus persica, Chaenomeles sinensis and Sorbus aucuparia. The HNLs from P. edulis (PeHNL), E. japonica (EjHNL), P. mume (PmHNL), and B. montanum (BmHNL) have been purified to homogeneity and their enzymatic properties characterized.
    In trying to expand the applicability of the HNL-catalyzed reaction, we focused on the potential for asymmetric synthesis. We describe the efforts to develop HNL-catalyzed reactions for the optically active cyanohydrin and β-nitro alcohol synthesis.
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  • Synthesis of Bacterial Glycoconjugates and Their Bio-functional Studies in Innate Immunity
    Koichi Fukase, Yukari Fujimoto, Atsushi Shimoyama, Katsunori Tanaka
    2012 Volume 70 Issue 2 Pages 113-130
    Published: February 01, 2012
    Released on J-STAGE: February 27, 2012
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.70.113
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    Immunostimulating glycoconjugates from bacteria were synthesized for elucidation of the recognition with innate immune receptors. Synthesis of partial structures and analogues of lipopolysaccharide and its bioactive principle ‘lipid A’ contributed the elucidation of mode of action, i.e., interaction of lipopolysaccharide with its receptor ‘TLR4/MD-2 complex’. Immunomodulation by parasitic bacteria ‘Helicobacter pylori’ was elucidated by using synthetic lipopolysaccharide partial structures. Intracellular peptidoglycan receptors, ‘Nod1’ and ‘Nod2’, and their ligand structures were identified by using synthetic peptidoglycan partial structures. New Nod1 ligands were identified from the bacterial supernatant. In vivo function of Nod1 was studied by using synthetic ligands found from small library of Nod1 ligands.
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  • Heavier Analogs of Carbene Complexes: Syntheses of a New Type of Silylene and Germylene Complexes and Their Reactions with Unsaturated Organic Compounds
    Hisako Hashimoto, Hiromi Tobita
    2012 Volume 70 Issue 2 Pages 131-141
    Published: February 01, 2012
    Released on J-STAGE: February 27, 2012
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.70.131
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    In comparison with carbene complexes having reactive M=C double bonds, their heavier analogs, i.e. silylene and germylene complexes, having M=E (E=Si, Ge) double bonds are also expected to show high reactivity. However, most of such complexes previously prepared have actually shown poor reactivity toward usual organic substrates, probably because their M=E double bonds are sterically overprotected for stabilization. Recently, we have succeeded in synthesizing silylene and germylene complexes having hydrogen atoms on both the metal center and E atom. The M=E double bonds of these complexes are indeed the least sterically protected in any known ones and can react smoothly with various substrates such as nitriles, ketones, heterocumulenes, etc. under mild conditions. Here we report the syntheses, structures, and novel reactions of these new silylene and germylene complexes.
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  • Development of Asymmetric Reactions Using Chiral Oxazolidine-type Catalysts
    Hiroto Nakano, Yuko Okuyama, Mitsuhiro Takeshita, Eunsang Kwon, Yoshih ...
    2012 Volume 70 Issue 2 Pages 142-153
    Published: February 01, 2012
    Released on J-STAGE: February 27, 2012
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.70.142
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    A design of a chiral ligand and the metal-coordinated catalyst is very important for achievement of a highly enantioselective catalytic asymmetric reactions. Recently, we developed the chiral oxazolidine ligands having N,O-acetal structure, such as phosphinooxazolidine (POZ), phosphinooxazinane (POZI) and oxazolidine (OZ). POZ and POZI afforded products in an excellent enantioselectivities in Pd-catalyzed asymmetric allylic alkylation and tandem allylation. Furthermore, cationic Pd-POZ catalysts showed high levels of catalytic activity in the asymmetric Diels-Alder (DA) reactions of some dienes with oxazolidinone- or pyrrazolidinone-type dienophiles. Cationic Pd-POZ catalyst showed an excellent catalytic activity in the DA reaction in ionic liquid (IL). The catalyst could be reused eight times without significant decrease of yield and enantioselectivity in IL/CH2Cl2 solvent system. OZ ligand also worked as organocatalyst in the DA reaction of 1,2-dihydropyridies with acroleins to afford the useful intermediate of Oseltamivir.
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  • Total Synthesis of Marine Halogen-Containing Triterpene Polyethers Using Regioselective 5-exo and 6-endo Cyclizations and the Stereochemistry
    Yoshiki Morimoto
    2012 Volume 70 Issue 2 Pages 154-165
    Published: February 01, 2012
    Released on J-STAGE: February 27, 2012
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.70.154
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    Aurilol (1), intricatetraol (3), and enshuol (5), marine halogen-containing members of a family of squalene-derived triterpene polyethers named oxasqualenoids, were isolated from the sea hare Dolabella auricularia, the red alga Laurencia inricata, and omaezakiana Masuda, respectively. Although their planar structures and partial configurations were elucidated by spectroscopic and chemical analyses, until now their entire configurations had not been determined. Many other types of oxasqualenoids have also been isolated from both marine and terrestrial organisms; however, it is often difficult to determine their stereostructures even by modern highly advanced spectroscopic methods, especially in the case of acyclic systems that include stereogenic quaternary carbon centers. Such systems expose the technical limitations of the current highly advanced NMR spectroscopic methods used for the structural elucidation of diverse and complex natural products. Herein, we report the total assignments of the previously incomplete stereostructures of 1, 3, and 5 to 2, 4, and 6, respectively, through the first asymmetric total syntheses featuring regioselective 5-exo and 6-endo cyclizations of bishomoepoxy alcohols.
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  • Development of Synthetic Methods for Peptide Thioesters Based on the N-S Acyl Shift Reaction
    Toru Kawakami, Saburo Aimoto
    2012 Volume 70 Issue 2 Pages 166-176
    Published: February 01, 2012
    Released on J-STAGE: February 27, 2012
    DOIhttps://doi.org/10.5059/yukigoseikyokaishi.70.166
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    Peptide thioesters are used as key building blocks for contemporary protein synthesis, based on the ligation strategy such as thioester method and native chemical ligation. We found the methods for preparation of the peptide thioesters, in which the key reaction is an intramolecular N-S acyl shift reaction of thiol-containing peptides. These processes can be applied to Fmoc based solid phase peptide synthesis with minimum racemization at the thioester position. For the N-S acyl shift reaction, we use an N-2-mercapto-4,5-dimethoxybenzyl (Dmmb) group on the peptide bond, or a cysteine residue. The Dmmb-containing peptide is readily converted to the corresponding 2-sulfoethyl thioester via the N-S acyl shift reaction, followed by the intermolecular thiol-thioester exchange reaction. A peptide containing a Cys-Pro ester (CPE) moiety is spontaneously transformed into a diketopiperazine (DKP) thioester under neutral conditions. Furthermore, a peptide containing a Cys-Pro-Cys (CPC) sequence was also transformed into a peptide DKP thioester under acidic conditions via the N-S acyl shift reaction.
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