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排序方式: 共有91条查询结果,搜索用时 31 毫秒
1.
2.
(R)-Tetrahydrozerumbone 2, which has a powerful balmy fragrance, contains a stereogenic carbon at the C2 position and can be easily prepared from zerumbone 1, one of the most important materials displaying an NMRDOS character. The reduction of 2 gave two diastereomers of tetrahydrozerumbol 3, and the optically active (>99%ee) alcohols were obtained by a lipase-catalyzed stereoselective transesterification of each racemic alcohol. A barrier to this development is a long reaction time (about four weeks) and the need to separate the diastereoisomers. The desired (2R)-form of 3 was efficiently obtained by a lipase-catalyzed transesterification under optimized conditions using a diastereomeric mixture of racemic 3 as the starting material without separation of the diastereomers. Using this method, the reaction of other zerumbone derivatives is greatly improved. 相似文献
3.
Takashi Kitayama Sayo Ohta Yasushi Kawai Tomoyasu Nakayama Masataka Awata 《Tetrahedron: Asymmetry》2010,21(1):11-15
Tetrahydrozerumbone 2, which has a powerful balmy fragrance, has a stereogenic carbon at C2 and can be easily prepared from zerumbone 1, which is one of the most important materials that displays an NMRDOS character. Reduction of 2 gave two diastereomers 3 and 4; their optically active (>99% ee) alcohols were obtained by lipase-catalyzed stereoselective transesterification of each racemic alcohol. The enantioselectivity of tetrahydrozerumbol does not entirely depend on the hydroxyl position but on the 2-methyl position. Compounds (R)-2 and (S)-2 were obtained by Dess–Martin oxidation of the corresponding alcohols. Interestingly, (R)-2 showed a strong balmy fragrance while (S)-2 had hardly any fragrance. 相似文献
4.
Eri?Takano Nobuaki?Shimura Takeshi?Akiba Yukiya?Kitayama Hirobumi?Sunayama Koichi?Abe Kazunori?Ikebukuro Toshifumi?TakeuchiEmail authorView authors OrcID profile 《Mikrochimica acta》2017,184(6):1595-1601
The authors describe a pipette type of biosensor for detecting target genes and using a zinc finger protein fused to luciferase (ZF luciferase). The ZF protein binds to a specific DNA sequence, and the target double-stranded (ds) DNA can be detected by monitoring the enzymatic activity of ZF luciferase. A small avidin-immobilized reaction plate is placed on a plastic pipette tip (referred to as Biologi tip). The dsDNA detection procedures are carried out by using a programmable dispensing robot equipped with a photodetector. These procedures include (a) the aspiration of an analyte to capture the biotinylated target dsDNA (a product of a polymerase chain reaction) on the small reaction plate inside the pipette tip, (b) the introduction of ZF luciferase and luciferin into the pipette tip, and (c) migration of the pipette tip to the detection port to measure bioluminescence on the small reaction plate. The emission originating from luciferase activity is observed on the reaction plate containing immobilized biotin-tagged target dsDNA, whereas plates containing non-target or biotinylated single-stranded DNA only do not yield a signal. The intensity of emission increases proportionally to the concentration of dsDNA, and the detection limit of the target dsDNA is as low as 62 pM. An actual genomic DNA sample from Escherichia coli O157 was successfully detected by this automatic analyzer using the Biologi tip equipped with a reaction plate. This indicates that this system has a large potential for practical applications, including in particular point-of-care analyses in hygiene control, food safety testing, and clinical diagnosis. 相似文献
5.
Takashi Kitayama Maki Nakahira Kae Yamasaki Hiromi Inoue Chika Imada Yuji Yonekura Masataka Awata Hikaru Takaya Yasushi Kawai Kohta Ohnishi Akira Murakami 《Tetrahedron》2013
Zerumbone 1, having powerful latent reactivity and containing two conjugated double bonds and a double conjugated carbonyl group is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. The conjugation system plays an important role in the expression of biological activity. N-Bromosuccinimide (NBS) reaction of 1 gave high reactive intermediate 2 with an exo-methylene group, which was obtained from 1 quantitatively. Treatment of 2 with nucleophiles gave various zerumbone-pendant derivatives, including C–H, C–O, C–N, and C–C bond formation, maintaining the conjugation system through SN2′-type reaction. Almost all zerumbone-pendant derivatives showed a good value of IC50 against the suppressive effect of NO generation. Among them, amine derivative 5, binding with 2 mol of zerumbone, showed the strongest activity (IC50: 0.24 μM). 相似文献
6.
Defect imaging using scanning laser source technique has been investigated for a plate with rounded defects and notch-type defects in our previous studies. This paper examines frequency dependence of the defect images with both calculations and experiments in order to acquire clearer images. Both calculation and experimental results for a straight notch revealed that clearer images of notch-type defects can be obtained in the range of low frequency-thickness product below about 200 kHz mm. Moreover, images of the defects of various shapes were obtained by synthesizing images from eight receiving transducers, and similarly to the case of the straight notches, they became more clearly in the low frequency range. 相似文献
7.
Fujiwara T Mohammadzai IU Kitayama K Funazumi Y Kumamaru T 《Journal of colloid and interface science》2007,310(2):682-685
Tris(2,2'-bipyridine) complex of iron(II) was found to cause an increase in the chemiluminescence (CL) emission of luminol dispersed in the reversed micellar medium of cetyltrimethylammonium chloride (CTAC) in 1:1 (v/v) dichloromethane-cyclohexane/water, when the iron(II) complex in dichloromethane was mixed directly with the reversed micellar solution containing luminol. Visible absorption measurements showed that, when dispersed in the CTAC reversed micellar medium, the iron(II) complex dissociates easily. In the reverse micelle, subsequently the free iron(II) ion produced may catalyze the CL oxidation of luminol even in the absence of hydrogen peroxide. The CL emission produced under the optimized experimental conditions was detectable at a minimum iron(II) concentration of 1.0 x 10(-9) M using a flow injection system. 相似文献
8.
Shimizu K Suzuki H Hayashi E Kodama T Tsuchiya Y Hagiwara H Kitayama Y 《Chemical communications (Cambridge, England)》2002,(10):1068-1069
Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction. 相似文献
9.
Bamba T Fukasaki W Kajiyama S Ute K Kitayama T Kobayashi A 《Journal of chromatography. A》2001,911(1):113-117
A high-resolution analysis of polyprenol mixtures was achieved by supercritical fluid chromatography (SFC). The separation of polyprenols was examined on an octadecylsilane-packed column with liquid carbon dioxide as the mobile phase and ethanol as modifier. Using this chromatography system, the resolution of separation (Rs) between octadecaprenol (prenol 18) and nonadecaprenol (prenol 19) was two times higher than that using conventional reversed-phase high-performance liquid chromatography. Our SFC technique allows the advantage of baseline separation of polyprenol samples containing hydrophobic components such as terpenes or fatty acids that are unfavorable for good separation. This method is very useful for the analysis of structurally close polyprenol analogues of rubber plant metabolites. 相似文献
10.
A Programmable Signaling Molecular Recognition Nanocavity Prepared by Molecular Imprinting and Post‐Imprinting Modifications 下载免费PDF全文
Ryo Horikawa Dr. Hirobumi Sunayama Dr. Yukiya Kitayama Dr. Eri Takano Prof. Dr. Toshifumi Takeuchi 《Angewandte Chemie (International ed. in English)》2016,55(42):13023-13027
Inspired by biosystems, a process is proposed for preparing next‐generation artificial polymer receptors with molecular recognition abilities capable of programmable site‐directed modification following construction of nanocavities to provide multi‐functionality. The proposed strategy involves strictly regulated multi‐step chemical modifications: 1) fabrication of scaffolds by molecular imprinting for use as molecular recognition fields possessing reactive sites for further modifications at pre‐determined positions, and 2) conjugation of appropriate functional groups with the reactive sites by post‐imprinting modifications to develop programmed functionalizations designed prior to polymerization, allowing independent introduction of multiple functional groups. The proposed strategy holds promise as a reliable, affordable, and versatile approach, facilitating the emergence of polymer‐based artificial antibodies bearing desirable functions that are beyond those of natural antibodies. 相似文献