Yoshimasa Makita

Bio: Yoshimasa Makita is an academic researcher from Osaka Dental University. The author has contributed to research in topics: Rotaxane & Zinc. The author has an hindex of 9, co-authored 38 publications receiving 303 citations. Previous affiliations of Yoshimasa Makita include Tokyo Institute of Technology & Osaka Prefecture University.

A zinc(II)-included hemicryptophane: facile synthesis, characterization, and catalytic activity.

Abstract: A zinc(II)-included hemicryptophane, which has a zinc(II) center embedded in the cavity, was synthesized and characterized. The catalytic activity of the hemicryptophane was tested in the hydrolysis of methyl para-nitrophenyl carbonate (MPC). A direct comparison between the hemicryptophane and the model complex, which lacks a cavity, demonstrated that the cage structure enhanced the catalytic activity.

Catalytic Asymmetric Synthesis and Optical Resolution of Planar Chiral Rotaxane

Abstract: Planar chiral rotaxanes were synthesized from crown ether and secondary ammonium salt via trialkylphosphane-catalyzed acylative end-capping. Their optical resolution was achieved by chiral HPLC after acylative neutralization of the ammonium group. When optically active trialkylphosphane 2 was used as the chiral acylation catalyst, optically active rotaxane (4.4% ee) was obtained.

Aromatic hydrocarbon-catalyzed direct reaction of sulfur and sodium in a heterogeneous system: selective and facile synthesis of sodium monosulfide and disulfide.

Abstract: Sodium disulfide and monosulfide were selectively formed via the direct reaction of sulfur and an equimolar amount of sodium in 1,2-dimethoxyethane at 70 °C in the presence of a catalytic amount of aromatic hydrocarbons and ketone.

Quantitative active transport in [2]rotaxane using a one-shot acylation reaction toward the linear molecular motor.

Abstract: A rotaxane consisting of a crown ether wheel and a secondary ammonium salt axle, on which a neopentyl-type end-cap was placed close to the ammonium moiety, was prepared. When the rotaxane was treated by excess triethylamine, the wheel component thermodynamically moved over the proximate neopentyl group to deconstruct the interlocked structure. The wheel component in the rotaxane, however, quantitatively moved against the proximate end-cap by the action of trifluoroacetic anhydride in the presence of excess triethylamine. This motion, which was driven by the simple one-shot acylation reaction, can be referred as the active transport. When the distant end-cap is of the neopentyl-type, the axle can be thermally dethreaded from the distant end-cap after the acylative transport. The series of the wheel movement controlled by the neopentyl group can be the basic motion of the unidirectional linear molecular motor.

Supramolecular catalysis. Part 2: artificial enzyme mimics

Abstract: The design of artificial catalysts able to compete with the catalytic proficiency of enzymes is an intense subject of research. Non-covalent interactions are thought to be involved in several properties of enzymatic catalysis, notably (i) the confinement of the substrates and the active site within a catalytic pocket, (ii) the creation of a hydrophobic pocket in water, (iii) self-replication properties and (iv) allosteric properties. The origins of the enhanced rates and high catalytic selectivities associated with these properties are still a matter of debate. Stabilisation of the transition state and favourable conformations of the active site and the product(s) are probably part of the answer. We present here artificial catalysts and biomacromolecule hybrid catalysts which constitute good models towards the development of truly competitive artificial enzymes.

Metal-Sulfur Battery Cathodes Based on PAN-Sulfur Composites.

Abstract: Sulfur/polyacrylonitrile composites provide a promising route toward cathode materials that overcome multiple, stubborn technical barriers to high-energy, rechargeable lithium-sulfur (Li-S) cells. Using a facile thermal synthesis procedure in which sulfur and polyacrylonitrile (PAN) are the only reactants, we create a family of sulfur/PAN (SPAN) nanocomposites in which sulfur is maintained as S3/S2 during all stages of the redox process. By entrapping these smaller molecular sulfur species in the cathode through covalent bonding to and physical confinement in a conductive host, these materials are shown to completely eliminate polysulfide dissolution and shuttling between lithium anode and sulfur cathode. We also show that, in the absence of any of the usual salt additives required to stabilize the anode in traditional Li-S cells, Li-SPAN cells cycle trouble free and at high Coulombic efficiencies in simple carbonate electrolytes. Electrochemical and spectroscopic analysis of the SPAN cathodes at various stages of charge and discharge further show a full and reversible reduction and oxidation between elemental sulfur and Li-ions in the electrolyte to produce Li2S as the only discharge product over hundreds of cycles of charge and discharge at fixed current densities.

Structure control of polysaccharide derivatives for efficient separation of enantiomers by chromatography

Abstract: Chirality is a ubiquitous feature in living systems. Today, it is widely recognized that many biologically interesting compounds, such as drugs, agrochemicals, food additives, and fragrances, are chiral and their physiological properties usually rely on their chirality due to the extremely high chiral discrimination ability of enzymes and receptors.1-6 Particularly, the different pharmacological effects between enantiomers are ultimately an important concern in the pharmaceutical field in which only one enantiomer of a chiral drug often exhibits the desirable therapeutic activity, while the other shows an antagonistic function, side effects, or even toxic effects.7-14 During the late 1950s and early 1960s, a racemate of N-phthalylglutamic acid imide, which is a sedative and hypnotic drug known as thalidomide, was administrated to pregnant women and caused the birth of approximately 10 000 babies with malformations. Later, Blaschke pointed out that this teratogenic effect was attributed to the S-(-)isomer.15 Even though the administration of the pure R-(+)isomer could not halt the disaster because thalidomide is unstable in the body and easily undergoes racemization,16-18 this tragedy undoubtedly brought a profound movement in the drug administration and industries. In 1992, the U.S. Food and Drug Administration issued a specific guideline for the production of new chiral drugs,19 which demanded a systematic investigation of the biological behavior of their individual enantiomers and significantly encouraged the development of single enantiomer drugs.20-22 Today, most of the best-selling drugs around the world are administered as single enantiomers with the desired therapeutic activity,23 and the annual sales of single enantiomer drugs are expected to exceed 200 billion dollars in 2008. Furthermore, the preparation of single enantiomers has also become important in the fields of functional materials, such as ferroelectric liquid crystals and organic nonlinear optical molecules.24-26 Based on this historical background, substantial efforts have been undertaken to develop practical techniques for the preparation of enantiomers with a high enantiomeric excess (ee). In general, two approaches are utilized for this objective, asymmetric synthesis and chiral separation. Asymmetric synthesis using chiral sources, such as chiral pools, chiral auxiliaries, asymmetric catalysts, and enzymes, has significantly progressed over the last few decades.27-41 Although the large-scale preparation of enantiomers can be economically attained using this approach, the products do not always show a high ee, and therefore, a further purification step may be inevitable. Additionally, nature produces only one of the enantiomers as a chiral source in most cases. This means that if both enantiomers of the target compounds are required, at least two kinds of chiral sources are necessary for each enantiomer. However, it is sometimes difficult to obtain both of them. On the other hand, the chiral separation approach can easily provide both enantiomers with a high ee. Since Pasteur first isolated two enantiomers of sodium ammonium tartrate using a magnifying glass and a pair of tweezers in 1848,42,43 the innovation of chiral separation techniques has attracted great interest. Basically, chiral separations44 are carried out by (i) crystallization,45-47 (ii) enzymatic kinetic resolution,48-50 and (iii) chromatographic separation.51-53 Specifically, direct chiral separation using chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) has significantly evolved during the past few decades and is recognized as the most popular and reliable tool for both the analysis of enantiomer compositions and the preparation of pure enantiomers.51-64 Chiral separations can * To whom correspondence should be addressed. Mailing address: EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 4648603, Japan. Phone: +81-52-789-4600. Fax: +81-52-789-3188. E-mail: okamoto@apchem.nagoya-u.ac.jp. † Nagoya University. ‡ Harbin Engineering University. Chem. Rev. 2009, 109, 6077–6101 6077