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Volume 62, Issue 7
Displaying 1-10 of 10 articles from this issue
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[in Japanese]2004 Volume 62 Issue 7 Pages 672
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (248K) -
Kenso Soai2004 Volume 62 Issue 7 Pages 673-681
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSHighly enantioselective asymmetric syntheses, i.e., enantioselective addition of alkylmetal reagents to aldehydes and imines, enantioselective conjugate addition of dialkylzincs to enones, and asymmetric autocatalysis have been developed by designing asymmetric catalysts (or chiral ligands) and chiral environment of the reactions. Automultiplication of chiral compounds by asymmetric autocatalysis was discovered where a chiral product acts as a chiral catalyst for its own production. Asymmetric autocatalysis with>99.5% ee in a yield of > 99% was attained using pyrimidyl alkanol as an asymmetric autocatalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde. The asymmetric autocatalysis exhibits significant positive non-linear effect on ee. Asymmetric autocatalyst with very low (ca. 0.00005%) ee enhances its ee significantly up to > 99.5% ee during the consecutive asymmetric autocatalysis without the assistance of any other chiral auxiliary. Moreover, amino acids and [6] helicene with very low ee which are produced by asymmetric photolysis and photosynthesis using circularly polarized light serve as chiral initiators of asymmetric autocatalysis, and pyrimidyl alkanol with high ee is obtained. Inorganic chiral crystals such as quartz and sodium chlorate, [2.2] paracyclophanes, allenes, chiral cobalt complexes due to the topology of coordination, chiral primary alcohols due to the deuterium substitution also work as chiral initiators. Asymmetric autocatalysis is capable to discriminate efficiently the chirality of various chiral compounds. Moreover, the reactions of pyrimidinecarbaldehyde with diisopropylzinc without adding chiral substance exhibit the formation of enantioenriched S or R pyrimidyl alkanols with approximate stochastic distribution, which indicates the reaction is a spontaneous absolute asymmetric synthesis. These results correlate for the first time the proposed origins of chirality of organic compounds with the chirality of organic compounds with very high ee.View full abstractDownload PDF (1495K) -
Shin Kamijo, Yoshinori Yamamoto2004 Volume 62 Issue 7 Pages 682-692
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe catalytic reactions involving π-allylpalladium complexes are one of the well-studied and established fields in organometallic chemistry. We have found entirely new types of catalytic transformations through a π-allylpalladium azide complex. The palladium-catalyzed three-component coupling (TCC) reaction of isocyanides, allyl methyl carbonate, and trimethylsilyl azide afforded allyl cyanamides via the π-allylpalladium mimic of Curtius rearrangement. This TCC reaction was further applied for the synthesis of N-cyanoindoles with employing 2-alkynylisocyanobenzenes as a starting material. The palladium-catalyzed TCC reaction of cyano compounds, allyl methyl carbonate, and trimethylsilyl azide also proceeded to give 2-allyltetrazoles regioselectively via the [3+2] cycloaddition between π-allylpalladium azide complex and cyanides. The regiospecific formation of 2-allyl-1, 2, 3-triazoles was observed when the TCC reaction was carried out with utilizing activated alkynes as a staring material instead of cyano compounds.View full abstractDownload PDF (1733K) -
Hideyuki Sato, Takeshi Oishi, Noritaka Chida2004 Volume 62 Issue 7 Pages 693-704
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSRecently, natural products containing highly functionalized α-substituted α-amino acid structures have been isolated and reported to show interesting biological properties such as neurotrophic, immunosuppressive, antifungal, and other activities. Efficient synthesis of these compounds, which are expected to be potent lead compounds for new drugs, is an important issue. In this article, development of the novel methodology for the synthesis of natural products in this class; rearrangement of allylic trichloroacetimidates (Overman rearrangement) on sugar scaffolds followed by further transformation of the rearranged products into highly functionalized α-substituted α-amino acid structures by use of the residual functionalities on sugars, is described. Overman rearrangement of imidates derived from aldohexofuranoses generated the tetrasubstituted carbon with nitrogen in a stereoselective manner. The rearranged products were efficiently converted into heterocyclic and acyclic natural products by, conventional reactions. Based on this methodology, total syntheses of lactacystin, myriocin, and sphingofungin E starting from aldohexofuranoses have been achieved. Utilization of Overman rearrangement in natural product synthesis is also shortly reviewed.View full abstractDownload PDF (1740K) -
Akio Kamimura2004 Volume 62 Issue 7 Pages 705-715
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSRecent development of synthetic reactions using the Michael addition of thiols or analogues is described. Nucloephilic attack of thiolate anions to α, β-unsaturated ketones or esters generates enolate anions which are active to perform aldol reaction when the reaction condition is kept away from protic media. High stereoselectivity as well as enantioselectivity is achieved for the Michael/aldol tandem reaction when appropriate reaction conditions are employed. High regioselective Michael addition of thiols to unsymmetric fumaric derivatives is also accomplished and the either of regioisomers is prepared in a highly selective manner. The thio-groups introduced by these reactions serve as a useful precursor of carbon radicals that efficiently undergo cyclization reaction to provide heterocyclic compounds diastereoselectively.View full abstractDownload PDF (1766K) -
Toshiyasu Sakakura, Hiroyuki Yasuda, Jun-Chul Choi2004 Volume 62 Issue 7 Pages 716-726
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe utilization of carbon dioxide in organic synthesis is developing rapidly. From an environmental point of view, carbon dioxide is very attractive as a substitute for organic solvents because it is non-toxic, non-flammable, and easily separable. In addition, carbon dioxide is stable under oxidative or radical conditions, and highly miscible with gases and fluorocarbons. On the other hand, the utilization of carbon dioxide as a renewable Ci building block has been a challenge for synthetic chemists. Especially, application as a phosgene alternative is quite promising. Recent progress in these areas is reviewd.View full abstractDownload PDF (1770K) -
Yoshito Takeuchi, Miki Nishikawa, Yusuke Sugiyama2004 Volume 62 Issue 7 Pages 727-736
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSHypercoordination (hypervalency) of some organo-silicon or -germanium compounds has attracted considerable attention. We were interested in hypercoordinated triarylgermane (1a) in which NMe2 group is the ligand. We prepared some analogs of la with a t-BuO (1b) or MeS (1c) group as the ligand in which the germanium atom was found hypercoordinated. We also prepared a series of derivatives of OMe (4a) species in which such substituents as halogen (4b-4d), Me (4e) or Ph (4f) were introduced. All compounds except 4f were found hypercoordinated though the structure varies depending on the nature of the substituent on germanium. A novel group of hypercoordinated organogermanium compounds was also prepared and their structure was elucidated. The dynamic behavior of these was explained in terms of pseudorotation. A method to prove the existence of hypercoordination of germanium atom was proposed based on the halfwidth of 73Ge NMR resonances.View full abstractDownload PDF (1490K) -
Mayumi Nishida, Tsuyoshi Tagata2004 Volume 62 Issue 7 Pages 737-742
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (782K) -
[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...2004 Volume 62 Issue 7 Pages 743
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (219K) -
2004 Volume 62 Issue 7 Pages 744-746
Published: July 01, 2004
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (633K)
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