巻号一覧
67 巻, 2 号
選択された号の論文の9件中1～9を表示しています
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巻頭言
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西山 繁2009 年 67 巻 2 号 p. 101
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル オープンアクセスPDF形式でダウンロード (515K)
総説および総合論文
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庄司 満, 林 雄二郎2009 年 67 巻 2 号 p. 102-113
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル 認証ありThe asymmetric total synthesis of epoxyquinols A, B, and C, and epoxytwinol A, and computational analysis of the key biomimetic oxidative dimerization, are described. In the first-generation synthesis, the HfCl4-mediated diastereoselective Diels-Alder reaction of furan with chiral acrylate has been developed. In the second-generation synthesis, a chromatography-free preparation of an iodolactone by using acryloyl chloride as the dienophile in the Diels-Alder reaction of furan, and the lipase-mediated kinetic resolution of a cyclohexenol derivative have been developed. A biomimetic cascade reaction involving oxidation, 6π-electrocyclization, and Diels-Alder dimerization or formal [4+4] cycloaddition, is the key reaction in the formation of heptacyclic structure of epoxyquinols A, B, and C, and epoxytwinol A. Intermolecular hydrogen-bonding is found to be the key, causing formation of both epoxyquinols A and B. In the dimerization of epoxyquinol monomer, two monomeric 2H-pyrans interact each other to afford pre-associated complexes stabilized by hydrogen-bonding, then Diels-Alder reaction proceeds.抄録全体を表示PDF形式でダウンロード (2483K) -
野地 匡裕, 石井 啓太郎2009 年 67 巻 2 号 p. 114-122
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル 認証ありThe rare earth metal and hafnium triflate-catalyzed cationic benzylation of various nucleophiles using benzylic alcohols is described. The reaction of benzylic alcohols with aromatic compounds in nitromethane in the presence of catalytic amount of metal triflate gave Friedel-Crafts-type benzylation products in high yield. Direct use of the alcohol as a source of an electrophile produces only water as a side product. Water-tolerant rare-earth metal triflates effectively catalyzed the alkylation under non-anhydrous conditions and the catalysts could be reused up to three times. The benzylation system also showed compatibility over a wide range of nucleophiles such as olefin, allylsilane, enol acetates, diketones, ketoesters, alcohols, and amides. The reaction conditions of various combinations of benzylic alcohols and nucleophiles were easily optimized by the two-dimensional catalysts-temperature screenings using La, Yb, Sc, and Hf triflates.抄録全体を表示PDF形式でダウンロード (1078K) -
石川 勇人, Dale L. Boger2009 年 67 巻 2 号 p. 123-133
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル 認証ありA concise 11-step total synthesis of (−)- and ent-(+)-vindoline is detailed based on a unique tandem intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole inspired by the natural product structure, in which three rings and four C-C bonds are formed central to the characteristic pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural product in a single step. As a key elements of the scope and stereochemical features of the reaction were defined, a series of related natural products of increasing complexity were also prepared by total synthesis including both enantiomers of vindorosine, minovine, 4-desacetoxyvindoline, 4-desacetoxy-5-desethylvindoline and 4-deaacetoxyvindorosine as well as N-methylaspidospermidine.抄録全体を表示PDF形式でダウンロード (1604K) -
樋口 恒彦2009 年 67 巻 2 号 p. 134-142
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル 認証ありA distinctive structural feature of P450 is the unusual thiolate coordination to heme. We have succeeded in the preparation of the first synthetic thiolato-iron porphyrin (SR complex) that retains its structure during catalytic oxidation.
Experiments using SR complex have revealed that the thiolate ligand greatly accelerates the rate of the O-O bond cleavage and its heterolysis even in highly hydrophobic media.
Prostaglandin H2 (PGH2) is catalytically isomerized to prostacyclin or thromboxane A2 by cytochrome P450s. We investigated the isomerization mechanism of PGH2 using SR complex, which is a model of P450 having heme-thiolate structure. Isomerization of endoperoxide proceeded very rapidly with SR, whereas imidazole or chloride-ligated heme had slight or no catalytic activity.
The results of kinetic isotope effects in the oxidative demethylation of p-dimethoxybenzene unambiguously showed that the formed active intermediates of heme-thiolates are different from those of hemes coordinated by imidazole or chloride.
Novel iron porphyrin-alkanethiolate complexes were prepared in order to examine the influence of the NH-S hydrogen bond on catalytic oxidation. The complexes were characterized by IR, EPR, resonance Raman spectroscopies and crystal structure analysis and their redox potentials were measured.
Our work also reports some spectroscopic and electrochemical properties of the first synthetic NO-heme-thiolate complex, prepared by treatment of SR with NO, relevant to NO synthase.抄録全体を表示PDF形式でダウンロード (2078K) -
伊藤 敏幸2009 年 67 巻 2 号 p. 143-155
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル 認証ありThe use of ionic liquids (ILs) to replace organic or aqueous solvents in biocatalysis processes has recently gained much attention and great progress has been accomplished in this area. This paper reviews our recent developments in the application of ionic liquids as solvents in enzymatic reactions. (1) The lipase recyclable use system has been accomplished using an ionic liquid solvent system. However, the reaction rate was gradually dropped with reputation of the process due to inhibitory action of acetaldehyde oligomer accumulated in the IL when vinyl acetate was used as acyl donor. This problem was solved when the reaction was carried out under reduced pressure conditions using methyl phenylthioacetate as acyl donor; there was no drop in the reaction rate despite five repetitions of the process in the [bmim][PF6] solvent system. We next attempted to evaluate the imidazolium salts again to see if they were suitable for recycling use of the enzyme using vinyl acetate as acyl donor. 1-Butyl-2,3-dimethylimidazolium tetrafluoroborate ([bdmim][BF4]) was thus found to be an excellent solvent to realize a perfect lipase-recycling system: no accumulation of an acetaldehyde oligomer was observed in this solvent system and it was possible to use the lipase repeatedly ten times while still maintaining perfect enantioselectivity and high reactivity. (2) Lipase PS from Burkholderia cepacia is one of the most widely used enzymes applicable for various substrates, however, the activity in non-aqueous media is reduced and it has been reported that the enantioselectivity is significantly dependent on the solvent system. A remarkable acceleration was accomplished by the alkylPEG sulfate imidazolium salt (IL1) coating with lipase PS in an i-Pr2O solvent system while maintaining excellent enantioselectivity: ca. 500- to 1,000-fold acceleration was recorded for some substrates with excellent enantioselectivity. Furthermore, we discovered that (R)-pyrrolidine-substituted imidazolium cetyl-PEG10-sulfate (D-ProMe) derived from D-proline worked as more excellent activating agent of lipase PS. (3) It is generally recognized that lipase-catalyzed reaction in an ionic liquid solvent proceeded slower than those in many conventional organic solvents. To overcome this problem, attempts have been made to evolve ionic liquids appropriate for lipase-catalyzed reaction. Very rapid lipase PS-catalyzed transesterification of secondary alcohols was achieved using 2-methoxyethyl(tri-n-butyl)phosphonium bis(trifluoromethanesulfonyl)imide (TU-P1) as solvent and afforded the first example of a reaction rate superior to that in diisopropyl ether.抄録全体を表示PDF形式でダウンロード (3837K) -
石曽根 隆2009 年 67 巻 2 号 p. 156-165
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル 認証ありThe coupling polymerization of 3,3'-dibromo-1,1'-biadamantane with magnesium gave the poly(1,3-adamantane) in good yield. The similar poly(1,3-adamantane)s could be obtained by the ring-opening polymerizations of 1,3-dehydroadamantanes (DHA) with trifluoromethanesulfonic acid. In the case of non-substituted DHA, the resulting polymer was not soluble in the various organic solvents. By contrast, the polymerization of butyl-substituted DHA gave the soluble poly(1,3-adamantane) in quantitative yield. DHA also underwent the spontaneous copolymerization with electron-deficient monomers such as acrylonitrile and methyl acrylate without catalyst to afford the alternating copolymers. The anionic polymerizations of 3-(methacryloyloxy)-1,1'-biadamantane, 4-(1-adamantyl)styrene, and 2-(1-adamantyl)-1,3-butadiene provided the stable living polymers possessing the predicted molecular weights and the narrow molecular weight distributions (Mw/Mn=1.1) in quantitative yields. The syntheses of polymers containing adamantyl groups in the main chain or the side chain are attained. All the polymers containing adamantyl skeletons showed high glass transition temperatures and high thermal properties, indicating the drastic effect of introduced adamantane moieties.抄録全体を表示PDF形式でダウンロード (1205K)
Review de Debut
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山口 潤一郎2009 年 67 巻 2 号 p. 166-167
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル オープンアクセスCatalytic enantioselective stereoablative reactions represent a unique approach to the preparation of enantioenriched materials, wherein a catalytic method destroys, at least temporarily, stereogenic elements of a molecule. This review introduces a recent example of novel approaches in asymmetric catalytic methods for stereoablation, as well as the use of a new stereoablative reaction in a concise synthesis of the marine diterpenoid (−)-cyanthiwigin F.抄録全体を表示PDF形式でダウンロード (629K)
十字路
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庄司 満, 石川 勇人, 樋口 恒彦2009 年 67 巻 2 号 p. 168
発行日: 2009/02/01
公開日: 2011/08/15
ジャーナル オープンアクセスPDF形式でダウンロード (502K)
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