研究者詳細 - 塚本　眞幸

論文 - 塚本　眞幸

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Enantiomeric products formed via different mechanisms: asymmetric hydrogenation of an α,β-unsaturated carboxylic acid involving a Ru(CH3COO)2[(R)-binap] catalyst 査読有り

M. Yoshimura, Y. Ishibashi, K. Miyata, Y. Bessho, M. Tsukamoto, and M. Kitamura

Tetrahedron 63 巻 ( 46 ) 頁： 11399-11409 2007年11月

Mechanism of Catalytic Asymmetric Hydrogenation of 2-Formyl-1-methylene-1,2,3,4-tetrahydroisoquinoline Using Ru(CH3COO)2[(S)-binap] 査読有り

M. Tsukamoto, M. Yoshimura, K. Tsuda, and M. Kitamura

Tetrahedron 62 巻 ( 23 ) 頁： 5448-5453 2006年6月

Origin of the Minor Enantiomeric Product in a Noyori Asymmetric Hydrogenation 査読有り

Y. Ishibashi, Y. Bessho, M. Yoshimura, M. Tsukamoto, and M. Kitamura

Angew. Chem. Int. Ed. 44 巻 ( 44 ) 頁： 7287-7290 2005年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

The enantiomeric products of the catalytic hydrogenation of an isotopically labeled substrate were separated. The ratios of the isotopomers revealed that the major and minor enantiomers are formed mostly through different mechanisms. Hence, when analyzing the energy profile of an asymmetric catalytic reaction with the Arrhenius equation, two competing diastereomorphic catalytic cycles should be considered.

ジホスフィンロジウムおよびルテニウム錯体を用いるデヒドロアミノ酸類の触媒的不斉水素化の機構研究の新展開査読有り

塚本眞幸, 北村雅人

有機合成化学協会誌 63 巻 ( 9 ) 頁： 899-910 2005年9月

Novel Synthesis and Characterization of Bioconjugate Block Copolymers Having Oligonucleotides 査読有り

A. Noro, Y. Nagata, M. Tsukamoto, Y. Hayakawa, A. Takano, and Y. Matsushita

Biomacromolecules 6 巻 ( 4 ) 頁： 2328-2333 2005年

Carboxylic Acids as Promoters for Internucleotide-Bond Formation via Condensation of a Nucleoside Phosphoramidite and a Nucleoside: Relationship between the Acidity and the Activity of the Promoter 査読有り

Y. Hayakawa, T. Iwase, E. J. Nurminen, M. Tsukamoto, and M. Kataoka

Tetrahedron 61 巻 ( 8 ) 頁： 2203-2209 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The relationship between the activity and the acidity of a carboxylic acid as a promoter for condensation of a nucleoside phosphoramidite and a nucleoside was investigated. The investigation revealed that the acid, the pKa value of which in acetonitrile is less than 18, is capable of promoting the condensation reaction, and acid with a pKa value outside of this range does not serve as a promoter. In carboxylic acids serving as promoters, the ones with higher acidity generally show greater activity. In particular, acids with a pKa value less than ca. 16 (measured by a potentiometric method), such as trichloroacetic acid (pKaZ10.6), trifluoroacetic acid (pKaZ12.7), dichloroacetic acid (pKaZ13.2 or 15.8), and 2,4-dinitrobenzoic acid (pKaZ16.1), show high levels of activity higher than that of conventionally used 1H-tetrazole. These carboxylic acids generally serve as excellent promoters for both the liquid-phase and the solid-phase synthesis of oligonucleotides via phosphoramidite method.

Is It Possible to Estimate the Enantioselectivity of a Chiral Catalyst from Its Racemic Mixture? 査読有り

F. Lagasse, M. Tsukamoto, C. J. Welch, and H. B. Kagan

J. Am. Chem. Soc. 125 巻 ( 25 ) 頁： 7490-7491 2003年

Recent Advances in the Measurement of Enantiomeric Excesses 査読有り

M. Tsukamoto and H. B. Kagan

Adv. Synth. Catal. 344 巻 ( 5 ) 頁： 453-463 2002年

Mechanism of Asymmetric Hydrogenation of α-(Acylamino)acrylic Esters Catalyzed by BINAP-Ruthenium(II) Diacetate 査読有り

M. Kitamura, M. Tsukamoto, Y. Bessho, M. Yoshimura, U. Kobs, M. Widhalm, and R. Noyori

J. Am. Chem. Soc. 124 巻 ( 23 ) 頁： 6649-6667 2002年

記述言語：英語掲載種別：研究論文（学術雑誌）

The mechanism of asymmetric hydrogenation of R-(acylamino)acrylic esters with Ru(CH3COO)2[(S)-binap] (BINAP ) 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl), giving the S saturated products in more than 90 per cent enantiomeric excess, has been investigated by means of a kinetic study, deuterium labeling experiments, isotope effect measurements, and NMR and X-ray analysis of certain Ru complexes. The hydrogenation in methanol under a low H2 pressure proceeds via a monohydride-unsaturate mechanism that involves the initial RuH formation followed by a reaction with an olefinic substrate. The migratory insertion in the enamide-RuH chelate complex occurs reversibly and endergonically in an exo manner, giving a five-membered metallacycle intermediate. The cleavage of the Ru-C bond is achieved with either H2 (major) or CH3OH (minor). Both of the pathways result in overall cis hydrogenation products. The hydrogen at C(3) is mainly from an H2 molecule, and the C(2) hydrogen is from another H2 or protic CH3OH. The major S and minor R enantiomers are produced via the same mechanism involving diastereomeric intermediates. The turnover rate is limited by the step of hydrogenolysis of a half-hydrogenated metallacyclic intermediate. The participation of two different hydrogen donor molecules is in contrast to the pairwise dihydrogenation using a single H2 molecule in the Rh(I)-catalyzed reaction which occurs via a dihydride mechanism. In addition, the sense of asymmetric induction is opposite to that observed with (S)-BINAP-Rh(I) catalysts. The origin of this phenomenon is interpreted in terms of stereocomplementary models of the enamide/metal chelate complexes. A series of model stoichiometric reactions mimicking the catalytic steps has indicated that most NMR-observable Ru complexes are not directly involved in the catalytic hydrogenation but are reservoirs of real catalytic complexes or even side products that retard the reaction.

Synthesis of α-Amino Phosphonic Acids by Asymmetric Hydrogenation 査読有り

M. Kitamura, M. Yoshimura, M. Tsukamoto, and R. Noyori

Enantiomer 1 巻 ( 4-6 ) 頁： 281-303 1996年

Conformational Study on 2-Acyl-1-alkylidene-1,2,3,4-tetrahydroisoquinolines 査読有り

M. Kitamura, M. Tsukamoto, H. Takaya, and R. Noyori

Bull. Chem. Soc. Jpn. 69 巻 ( 6 ) 頁： 1695-1700 1996年

General Asymmetric Synthesis of Isoquinoline Alkaloids. Enantioselective Hydrogenation of Enamides Catalyzed by BINAP-Ruthenium(II) Complexes 査読有り

M. Kitamura, Yi Hsiao, M. Ohta, M. Tsukamoto, T. Ohta, H. Takaya, and R. Noyori

J. Org. Chem. 59 巻 ( 2 ) 頁： 297-310 1994年

Applicability of a Standardized Discrete Cosine Transform Coding Method to Character Images 査読有り

Y. Hoshino, D. Ando, S. Higashino, and M. Tsukamoto

J. Electronic Imaging 1 巻 ( 3 ) 頁： 322-327 1992年

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