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Volume 53, Issue 1
Displaying 1-8 of 8 articles from this issue
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Akira OKU1995 Volume 53 Issue 1 Pages 2-12
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSα-Haloorganometallic compounds (the so-called carbenoids) are versatile reagents that possess ambiphilic reactivity. In addition to their well-studied nucleophilic character illustrated as α-halocarbanions (XCH2-), their synthetic potentiality as α-metallated carbocations (MCH2+) has been extensively studied by the author's group particularly in the following three categories ; (1) Highly effective as well as regio- and stereoselective C-H insertion reactions at the α-position of alkoxides ; (2) Designing zincate carbenoids, a novel type of carbenoid, as synthetically versatile reagents for highly selective tandem C-C bond formation reactions ; (3) Designing [1, n] -ambiphiles (or [1, n] -carbenoids) based on zincate carbenoids ; (4) Utilization of ethereal oxonium ylides, transiently generated from rhodium ketocarbenes and cyclic ethers, for the synthesis of mediumsized cyclic ketoethers Principal basis of the study is the manipulation of electrophilicity of carbenoides, which must be exerted first, followed by an easy control of the remaining nucleophilicity.. To ascertain as well as extend synthetic versatility of carbenoids, the mechanisms that control both regio- and stereoselectivity of the reactions were investigated in detail.View full abstractDownload PDF (1203K) -
Kiyoyuki YAMADA, Hideo KIGOSHI1995 Volume 53 Issue 1 Pages 13-21
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSSynthetic studies on the bracken ultimate carcinogen (3) and its artificial analogues (32, 33) are described. The synthesis of (-) -ptaquilosin (2) the aglycon of a potent carcinogen ptaquiloside (1) from bracken and its (+) - enantiomer (ent- 2) was achieved starting with (+) -dimenthyl (1R, 2R) -cyclopentane-1, 2-dicarboxylate. Dehydration of ptaquilosin (2) under weakly basic conditions led to the ultimate carcinogen (3). DNA cleaving activities of both enantiomers (3) were compared, the one (3) derived from natural (-) -ptaquilosin (2) being more efficient. Reactivities of the ultimate carcinogen (3) toward DNA are described. DNA was shown to be alkylated at the particular sites of purine bases and to undergo cleavage. The molecular mechanism of DNA cleavage with the ultimate carcinogen (3) was disclosed using deoxytetranucleotide d (GTAC) as a model DNA substrate.View full abstractDownload PDF (929K) -
Koji ARAKI1995 Volume 53 Issue 1 Pages 22-31
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSThe conformational changes among several conformational isomers of calix [4] arenes can take place because the OH groups rotate through the annulus. This inversion was inhibited by the introduction of the substituents bulkier than ethyl group into the OH groups and the resulting conformational isomers were separated. The selective syntheses of all partially O-propylated compounds and conformational isomers in p-tert-butylcalix [4] arene were successful by the combination of protection-deprotection method and the optimization of the reaction conditions (base, temperature, solvent, etc). Several of these compounds can possess the chirality which is caused by the disappearance of the symmetries on the conformation or based on the order in the array of different substituents. We succeeded in the syntheses and the optical resolutions of these calixarenes with molecular chirality for the first time.View full abstractDownload PDF (1174K) -
Takeshi SUGAI, Shigeo TSUCHIYA, Naoki MODHIZUKI, Hiromichi OHTA1995 Volume 53 Issue 1 Pages 32-42
Published: January 01, 1995
Released on J-STAGE: January 28, 2010
JOURNAL FREE ACCESSOptically active hydroxy acids have growing interests as the starting material of biologically active natural products. The authors have been studying the application of biocatalysts to the asymmetric synthesis of hydroxy acids. In this article, the following topics are shortly reviewed : 1) lipase-catalyzed kinetic resolution of α-benzyloxy esters;2) preparation and the synthetic utilization of optically active cyanohydrins;3) preparation of optically active mandelic acid via stereoselective oxido-reduction;4) lipase-catalyzed kinetic resolution of α- and, β-hydroxy acids;5) stereoselective reduction of β-keto esters;6) kinetic resolution in lipase-catalyzed lactonization;7) aldolase-catalyzed synthesis of sialic acid and its analogs.View full abstractDownload PDF (1328K) -
Kenji UNEYAMA1995 Volume 53 Issue 1 Pages 43-52
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSPreparation and reaction of trifluoroacetimidoyl halides 1 a (X=Cl), b (X=Br), c (X=I) have been summarized. Chemistries of three types of reactive intermediates, trifluoroacetimidoyl carbocations, carbanions and radicals were discussed. Reactions of 1 a with various nucleophiles proceeded smoothly, while palladation, zincation and lithiation of 1 c enabled carbon-carbon bond formation with electrophiles at the imidoyl carbon Meanwhile, photolysis of 1 c provided the corresponding radicals which underwent intramolecular cyclization leading to 2-trifluoromethylindoles.View full abstractDownload PDF (1061K) -
Jun-ichi YOSHIDA1995 Volume 53 Issue 1 Pages 53-63
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSGroup 14 metals such as silicon, germanium, and tin promote electron-transfer from a π-system and a heteroatom situated at the β position. On the basis of this effect, several electroorganic rections have been developed. Especially, the effective inter- and intra-molecular carbon-carbon bond formation reactions have been achieved by anodic oxidation of heteroatom-substituted organotin compounds.View full abstractDownload PDF (1260K) -
Kazunori NUKUI1995 Volume 53 Issue 1 Pages 64-66
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSDownload PDF (232K) -
[in Japanese], [in Japanese], [in Japanese], [in Japanese]1995 Volume 53 Issue 1 Pages 67
Published: January 01, 1995
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSDownload PDF (162K)
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