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Volume 61, Issue 6
Displaying 1-8 of 8 articles from this issue
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Tohru Oishi2003 Volume 61 Issue 6 Pages 562-571
Published: June 01, 2003
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSCiguatoxins are the causative neurotoxins of ciguatera seafood poisoning, and more than 20, 000 people suffer annually from ciguatera disease in subtropical and tropical regions. The extremely low content of ciguatoxins in fish has hampered the isolation and detailed biological studies. The complicated and huge, 3 nm long, molecular structure of ciguatoxins has impeded synthetic chemists from completing their total syntheses, which are formidable synthetic challenge in modern organic synthesis. Our highly convergent strategic approach featuring the chemoselective ring closing metathesis (RCM) reaction as a key tactics, (i) alkylative coupling and RCM, (ii) intramolecular carbonyl olefination and reductive etherification, (iii) chemo-and regioselective radical cyclization and RCM, has enabled the first total synthesis of ciguatoxin CTX 3 C, which will provide the practical supply for further studies.View full abstractDownload PDF (1722K) -
Shuichi Oi, Yoshio Inoue2003 Volume 61 Issue 6 Pages 572-582
Published: June 01, 2003
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSRecent progress on the rhodium-catalyzed addition reactions of organometallic reagents to carbon-hetero atom and electron deficient carbon-carbon double bonds in such as aldehydes, ketones, imines, and α, β-unsaturated carbonyl compounds are described. The reactions are considered to involve the generation of the organorhodium intermediate by the transmetalation with the organometallic reagents, which actually adds to the substrates. A wide range of organometallic reagents such as tin, boron, silicon, lead, bismuth, titanium, and zirconium can be employed in these catalytic addition reactions. Highly enantioselective asymmetric additions have also been achieved using chiral ligands for rhodium complexes.View full abstractDownload PDF (1636K) -
Shin-ichi Watanabe, Tadashi Kataoka2003 Volume 61 Issue 6 Pages 583-594
Published: June 01, 2003
Released on J-STAGE: January 22, 2010
JOURNAL FREE ACCESSThe syntheses, reactivities and utilization as versatile synthons of alkynyl and alkenylselenoni-um salts are described. Alkynylselenonium salts were prepared from the reaction of diaryl selenoxides and trimethylsilylphenylacetylene with triflic anhydride as a Lewis acid in high yields. Styrylselenonium salts were also derived from β-trimethylsilylstyrene by similar procedures. Alkynylselenonium salts acted as Michael acceptors or alkynyl cations against nucleophiles and reacted with active methylene carbanions to give furan derivatives via a selenurane intermediate. β-Phenylsufonylvinylselenonium salts, which were prepared from alkynylselenonium salts and benzenesulfinic acid, were the useful precursors of alkenyl cations and gave various β-substituted vinyl sulfones by the reaction with nucleophiles. β-Substituted vinyl sulfides were also synthesized from the reaction of β-arylthiovinylselenonium salts with nucleophiles. Vinylselenonium ylides, which were formed by the reaction of styrylselenonium salts with potassium hydride, reacted with aldehydes to afford chalcone derivatives.View full abstractDownload PDF (2030K) -
Masakatsu Matsumoto2003 Volume 61 Issue 6 Pages 595-604
Published: June 01, 2003
Released on J-STAGE: January 22, 2010
JOURNAL FREE ACCESSSimple 1, 2-dioxetanes generate mainly triplet-excited carbonyl fragments on thermal decomposition, whereas dioxetanes substituted with an aromatic electron donor display intramolecular chemically initiated electron exchange luminescence (CIEEL), in which an electron transfer from an electron donor to the dioxetane ring occurs to induce its decomposition, emitting light. After the discovery of an adamantylidenedioxetane bearing a 3-siloxyphenyl moiety, a wide variety of CIEEL-active dioxetanes have been synthesized and examined with a view to understanding chemiluminescent and biloluminescent mechanisms and applying these reactions to modern biological analysis. We describe here our study on design and synthesis of new CIEEL-type dioxetanes emitting light with high efficiency and also discuss the chemiexcitation process in the intramolecular CIEEL in aqueous system as well as in aprotic medium.View full abstractDownload PDF (1819K) -
Motohiro Akazome, Katsuyuki Ogura2003 Volume 61 Issue 6 Pages 605-613
Published: June 01, 2003
Released on J-STAGE: January 22, 2010
JOURNAL FREE ACCESSCrystalline dipeptides, (R) -arylglycyl- (R) -arylglycines (aryl = phenyl or naphthyl), have a straight glycylglycine backbone to construct a two-dimensional layer by intermolecular salt formation between COOH and NH2 groups. Guest molecules are included between the layers via host-guest interactions such as hydrogen bonding, aromaticaromatic interaction, and CH/πinteraction.
α-Hydroxy esters and sulfoxides were recognized with high enantioselectivity to be included in the chiral cavities. Motifs of the dipeptide aggregation depend on the kinds of guests : sulfoxide and ether guests assemble the dipeptide molecules in parallel, whereas α-hydroxy esters arrange them in antiparallel. Interestingly, the peptide recognized poly (ethylene glycol) s, which penetrated through the crystal lattice. Longer polymers were preferably recognized and the inclusion crystals became more thermally stable. We also demonstrated that these simple dipeptide hosts change their conformation according to the shape of the guest. This seems like a flexible model for the recognition of substrates by enzymes.View full abstractDownload PDF (2243K) -
Kiyohiko Kawai, Tetsuro Majima2003 Volume 61 Issue 6 Pages 614-619
Published: June 01, 2003
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSTo elucidate the hole transfer in DNA including multi-step processes, we used pulse radiolysis which provides a system for the hole transfer process free from charge recombination. Hole gen-erated in DNA was monitored by the transient absorption of radical cation of end-capped pyrene (pyrene.+) during pulse radiolysis of pyrene-conjugated oligodeoxynucleotides with different num-bers of intervening A-T base pairs between the G-region (5'-GTGTGTG-3') and pyrene. The results demonstrated a distance dependence of the hole transfer from G radical cation (G.+) to pyrene. This method revealed the hole transfer in DNA over the period of 100, us, which strongly suggests that G (-H.+) . : C (+H+) + can be present in DNA more than 100, us, and that this long life-time is at the very origin of the long-range hole transfer in DNA. We also determined a distance dependence of the single-step hole transfer process as β = 0.6 Å-1 which is consistent with that of the photoinduced single-step electron transfer in DNA.View full abstractDownload PDF (981K) -
Tohru Fukuyama2003 Volume 61 Issue 6 Pages 620-630
Published: June 01, 2003
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDuring the course of total synthesis of natural products, synthetic chemists would frequently encounter serious problems that require either development of new synthetic methodologies or novel designs in synthetic routes. In this context, the total synthesis of antibiotic 593 A could be completed because of p-methoxymethoxyphenylamine, a novel and practical protecting group for β-lactams. Reduction of thiolesters to aldehydes by means of triethylsilane and palladium on carbon could be discovered fortuitously during the total synthesis of porothramycin B. In order to carry out a biomimetic total synthesis of vincadifformine using our first-generation indole synthe-sis, we developed the chemistry of 2, 4-dinitrobenzenesulfonamides which could be deprotected under extremely mild conditions. More stable 2-nitrobenzenesulfonamides now finds widespread use for preparation of secondary amines from primary amines. Failure to introduce an sp3 carbon to the 2-position of indoles by means of the first-generation protocol forced us to develop another one in which o-alkenylthioanilides undergo radical cyclization to give 2, 3-disubstituted indoles. Combination of the second-generation indole synthesis and the chemistry of nitrobenzenesulfon-amide culminated in the first de novo total synthesis of ( ) -vinblastine.View full abstractDownload PDF (1542K) -
[in Japanese], [in Japanese], [in Japanese]2003 Volume 61 Issue 6 Pages 631
Published: June 01, 2003
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (223K)
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