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61.
Isiaka A. Owolabi U.V. Subba Reddy Madhu Chennapuram Chigusa Seki Yuko Okuyama Eunsang Kwon Koji Uwai Michio Tokiwa Mitsuhiro Takeshita Hiroto Nakano 《Tetrahedron》2018,74(36):4705-4711
A new type of amino amide organocatalysts was designed and synthesized from commercially available amino acids in easy steps. Their catalytic activities were examined in enantioselective crossed aldol reaction of various acyclic and cyclic ketones with aromatic aldehydes to afford the corresponding chiral anti-aldol adducts with good to excellent chemical yields, diastereoselectivities and enantioselectivities (up to 99%, up to syn:anti?=?1:99, up to 97% ee). 相似文献
62.
Izumi Sakamoto Kazuya Iwaoka Yuta Kawada Takanori Naito Kazuyoshi Makida Yuki Takeuchi Takeshi Nishii Mitsuyo Horikawa Hiroto Kaku Tetsuto Tsunoda 《Tetrahedron》2018,74(24):3052-3060
3,3-Dimethoxypropylsulfonyl (Dimps) chloride was prepared and used as a new versatile sulfonating agent for ammonia, primary and secondary amines to afford corresponding Dimps-amides in excellent yields. The resulting N-nonsubstituted and N-monosubstituted Dimps-amides, activated amines, were alkylated satisfactorily under new Mitsunobu conditions. The Dimps group was removed by treatment in aqueous solution under acidic followed by basic conditions. Furthermore, epilachnene, the defensive droplets from the Mexican bean beetle, Epilachna varivestis, was synthesized utilizing this Dimps methodology in short steps. 相似文献
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65.
Hiroto Watanabe 《Tetrahedron letters》2007,48(46):8132-8137
Oxygenation of fullerene took place under mechanical stressing by a simple vibration mill in an oxygen atmosphere at 1 atm. Milled products were mixtures of poly-oxidized fullerene, C60On, containing C-O-C and CO bonds. We observed a concurrent reaction as well, that is, polymerization of C60 and C60O. The average number of oxygen, n, of the overall products obtained by milling for 5 h was 8.6 per molecule of C60. We confirmed generation of singlet oxygen during the present mechanochemical reaction by an ESR spin trapping method. Trapping of 1O2 was completely inhibited the oxygenation of fullerene. Formation of 1O2 is attributed to the energy transfer from mechanically excited state of fullerene and plays a decisive role on the present oxygenation of fullerene under mechanical stressing in O2. In contrast, no 1O2 was observed by mechanically stressing the conventional photo-sensitizer, rosebengal. The difference in the behavior of C60 and rosebengal is interpreted in terms of molecular deformation, being much easier for a 3D molecule, C60, than a planar molecule, in line with the concept of inverse Jahn-Teller effects. 相似文献
66.
El-Mashtoly SF Takahashi H Shimizu T Kitagawa T 《Journal of the American Chemical Society》2007,129(12):3556-3563
The direct oxygen sensor protein from Escherichia coli (Ec DOS) is a heme-based signal transducer protein responsible for phosphodiesterase (PDE) activity. Binding of either O2 or CO molecule to a reduced heme enhances the PDE activity toward 3',5'-cyclic diguanylic acid. We report ultraviolet resonance Raman (UVRR) spectroscopic investigations of the reduced, O2- and CO-bound forms of heme-bound PAS domain of Ec DOS. The UVRR results show that heme discriminates different ligands, resulting in altered conformations in the protein moiety. Specifically, the environment around Trp53 that contacts the 2-vinyl group of heme, is changed to a more hydrophobic environment by O2 binding, whereas it is changed to a more hydrophilic environment by CO-binding. In addition, the PDE activity of the O2- and CO-bound forms for the Trp53Phe mutant is significantly decreased compared with that of the wild type (WT), demonstrating the importance of Trp53 for the catalytic reaction. On the other hand, the binding of O2 or CO to the heme produces drastic changes in the Tyr126 of Ibeta-strand at the surface of the sensor domain. Furthermore, we found that Asn84 forms a hydrogen bond with Tyr126 either in the O2- or CO-bound forms but not in the reduced form. Finally, the PDE activities of the ligand-bound forms for Asn84Val and Tyr126Phe mutants are significantly reduced as compared with that of WT, suggesting the importance of the hydrogen-bonding network from heme 6-propionate to Tyr126 through Asn84 in signal transmission. 相似文献
67.
Chiral cationic palladium-phosphinooxazolidine catalysts in ionic liquid afforded excellent enantioselectivity in Diels-Alder reactions and the catalyst was easily recycled eight times without any significant decrease in chemical yields or enantioselectivity (89-99%, 88-99% ee). 相似文献
68.
Yoshida H Mimura Y Ohshita J Kunai A 《Chemical communications (Cambridge, England)》2007,(23):2405-2407
Arynes were found to insert into carbon-halogen sigma-bonds of various acid halides, enabling acyl and halogen moieties to be introduced simultaneously into adjacent positions of aromatic rings. 相似文献
69.
Simultaneous Measurement of Individual ATPase and Mechanical Reactions by a Single Myosin Molecule at Work 总被引:1,自引:0,他引:1
Based on techniques for single molecule imaging and nanomanipulation by optical tweezers, we have developed a new technique that allows simultaneous measurement of individual ATPase and mechanical reactions from a single myosin molecule during force generation. We show how the ATPase reaction couples to the mechanical reaction directly at the single molecule level. The results show that the myosin head can produce force even after releasing the bound nucleotide, probably ADP, suggesting that the chemical energy driven by ATP hydrolysis can be hysteretically stored in the myosin molecule. This view does not support a widely accepted hypothesis in which the force generation is tightly coupled to ligand dissociation.This paper was originally presented as an invited paper at the seventh Meeting on Near Field Optics, which was held on July 1, 1998 at Nagoya University, Nagoya, organized by the Research Group on Near Field Optics of the Optical Society of Japan, an affiliate of the Japan Society of Applied Physics. 相似文献
70.