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131.
Xiang T Shibuya M Katsube Y Tsutsumi T Otsuka M Zhang H Masuda K Ebizuka Y 《Organic letters》2006,8(13):2835-2838
[structure: see text] Thirteen oxidosqualene cyclase homologues exist in the genome of Arabidopsis thaliana. One of these genes, At4g15340, was amplified by PCR and expressed in yeast. The yeast transformant accumulated tricyclic triterpene, (3S,13R)-malabarica-17,21-dien-3,14-diol (arabidiol), whose structure was determined by NMR and MS analyses. Its epoxide analogue, (3S,13R,21S)-malabarica-17-en-20,21-epoxy-3,14-diol (arabidiol 20,21-epoxide), was also isolated from the transformed yeast. This is the first example of a triterpene synthase that yields a tricyclic triterpene with two hydroxyl groups. 相似文献
132.
Kushiro T Hoshino M Tsutsumi T Kawai K Shiro M Shibuya M Ebizuka Y 《Organic letters》2006,8(24):5589-5592
Arabidopsis thaliana LUP1 (At1g78970) catalyzes the cyclization of oxidosqualene into lupeol and 3beta,20-dihydroxylupane (lupanediol). The stereochemical course of water addition to the lupanyl cation was studied. The X-ray crystal structure of lupanylepoxide 3,5-dinitrobenzoate established the configuration of epoxide as 20S. LiAlD4 reduction of the epoxide enabled the chemical shift assignment of prochiral methyl groups at C20 of lupanediol. Correlation of these methyl groups with biosynthetic lupanediol from [1,2-(13)C(2)] acetate established the stereochemical course of water addition. [reaction: see text]. 相似文献
133.
We present a new high-speed phase distribution measurement, in which a polarization imaging camera is applied to a quadrature
phase-shifting interferometer. The polarization imaging camera composed of a polarizer-mask on a detector array can provide
simultaneously two phase-shifted data in quadrature. Two sets of two phase-shifted data in quadrature are obtained before
and after a change of the interferometer such as object displacement or environmental disturbances. Phase sum and difference
distributions of the interferograms between two states with arbitrary phase-shift in the interferometer are calculated with
the two sets of two phase-shifted data in quadrature. This phase calculation method in the pixel displaced phase-shift method
has such advantage that phase-shifted data required for the calculation of phase distributions can be obtained by only two
pixels in the polarizer-mask detector array, which means no reduction of the image resolution in the other direction. The
principle of this technique and experimental results are presented. 相似文献
134.
Masato Shibuya 《Optical Review》1997,4(1):151-160
Production of a fine pattern is necessary to get a high integration degree of integrated circuits. The conventional methods
which utilize high numerical aperture and short wavelength exposure are limited by designing and manufacturing of a practical
lens and make the focus depth narrow. Resolution enhancement techniques (RETs) have, therefore, been required and proposed.
This paper introduces a phase-shifting mask, a typical RET, points out the problems and inconsistencies of conventional optical
imaging theory and explains the image formation concept of expansion of plane waves. Essentially using this concept, an attempt
is also made to describe some other typical RETs with potential. 相似文献
135.
Experimental wavelet analysis of flexural waves in beams 总被引:10,自引:0,他引:10
The wavelet transform (WT) is applied to the time-frequency analysis of flexural waves in beams. The WT with the Gabor wavelet
decomposes a dispersive wave into each frequency component in the time domain, which enables one to determine the traveling
time of a wave along the beam at each frequency. By utilizing this fact, a method is developed to identify the dispersion
relation and impact site of beams. 相似文献
136.
Ichiro Suzuki Akira ShigenagaAtsuo Manabe Hisao NemotoMasayuki Shibuya 《Tetrahedron》2003,59(30):5691-5704
The synthesis and Myers-Saito type cycloaromatization reactions of 10-membered enediynes containing a sulfone or a sulfoxide moiety are described. These enediynes cycloaromatized smoothly under physiological conditions to generate bioactive α,3-didehydrotoluene biradicals, that showed potent DNA damaging abilities. Further, in the presence of a nucleophile such as amine or sulfide, cycloaromatization did not occur following the radical reaction pathway but ionically induced cycloaromatization took place. 相似文献
137.
138.
139.
In order to reveal the anticlastogenic potency of aspirin, we evaluated the suppressive ability of aspirin on chromosome aberrations induced by X-ray. Aspirin at doses of 0.5, 5 and 50 mg/kg was administrated intraperitoneally or orally at 0.5 h after or before the X-ray irradiation. The anticlastogenic activity of aspirin on chromosome aberrations induced by X-ray was determined in the mouse micronucleus test and alkaline single cell gel electrophoresis (SCG) assay in vivo. The frequency by polychromatic erythrocytes with micronuclei (MNPCEs) was decreased by about 19–61% at 0.5 h after and about 23–62% at 0.5 h before the X-ray irradiation. DNA damage by X-ray was significantly decreased by oral administration of aspirin at 0.5 h after or before the X-ray irradiation for the SCG assay. We consider aspirin can be used as preventive agents against exposure of X-ray. 相似文献
140.
Dr. Masatoshi Shibuya Miki Matsuda Prof. Yoshihiko Yamamoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(34):8822-8831
We report the novel single-step 1,2-dicarbofunctionalization of an arylacetylene with an allylsilane and tris(pentafluorophenyl)borane [B(C6F5)3] involving C−C bond formation with C−H bond scission at the β-position to the silicon atom of an allylsilane and B→C migration of a C6F5 group. The 1,2-carbopentafluorophenylation occurs smoothly without the requirement for a catalyst or heating. Mechanistic studies suggest that the metallomimetic “pull-push” reactivity of B(C6F5)3 imparts consecutive electrophilic and nucleophilic characteristics to the benzylic carbon of the arylacetylene. Subsequent photochemical 6π-electrocyclization affords tetrafluoronaphthalenes, which are important in the pharmaceutical and materials sciences. Owing to the unique reactivity of B(C6F5)3, the 1,2-carbopentafluorophenylation using 2-substituted furan proceeded with ring opening, and the reaction using silyl enolates formed a C−C bond with C−O bond scission at the silyloxy-substituted carbon. 相似文献