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611.
Susumu Tajima Tamae Yanagisawa Tadashige Azami Toshikazu Tsuchiya 《Journal of mass spectrometry : JMS》1980,15(12):609-612
The temperature effect on the single and double hydrogen atom transfer reactions in o-, m- and p-toluic acid n-butyl esters and isobutyl esters has been investigated. For the meta and para isomers, the abundance of the m/z 137 ion [C8H9O2]+ generated by a double hydrogen atom transfer reaction increases relative to the m/z 136 ion [C8H8O2]+˙ generated by a single hydrogen atom transfer reaction upon lowering the temperature of the ionization chamber. On the other hand, the ratio of the peak abundances [137]+/[136]+ for the ortho isomers is nearly constant when the temperature is changed. It is shown that this is due to the difference between the appearance energies of the m/z 136 and m/z 137 ions. 相似文献
612.
Susumu Tajima Tadashige Azami Toshikazu Tsuchiya 《Journal of mass spectrometry : JMS》1977,12(1):24-27
The decomposition of the [C6H5CO]+ ions produced from eight alkyl benzoates by electron impact has been studied. By calculating the heat of formation of [C6H5CO]+ ions from the appearance potential value, it is shown that the ions from C6H5COOR when R?H, CH3, C2H5 have some excess energy, and those where R = n-C3H7, iso-C3H7, n-C4H9, iso-C4H9, iso-C5H11 are produced with more excess energy. It is also shown that by taking this excess energy into account, there is a linear relationship between the heat of formation of the activated complex produced in the reaction [C6H5CO]+→[C6H5]+ + CO and the vibrational degree of freedom of the neutral fragment ? OR. 相似文献
613.
Dependent on the selection of the light sources employed, the photoinduced iodoperfluoroalkylation of a variety of unsaturated compounds takes place efficiently via a radical mechanism. Upon irradiation with a xenon lamp through Pyrex (hnu >300 nm), terminal alkenes (R-CH=CH2) and alkynes (R-C triple bond CH) undergo iodoperfluoroalkylation with perfluoroalkyl iodides (RF-I) regioselectively, providing R-CH(I)-CH2-RF and R-C(I)=CH-RF, respectively. In the case of terminal allenes (R-CH=C=CH2), the photoinduced iodoperfluoroalkylation occurs selectively at the terminal double bond, giving the corresponding beta-perfluoroalkylated vinylic iodides (R-CH=C(I)-CH2-RF) in good yields. The photoinitiated reaction of vinylcyclopropanes (c-C3H5-C(R)=CH2) with RF-I proceeds via the rearrangement of cyclopropylcarbinyl radical intermediates to the homoallylic radical intermediates, and the corresponding 1,5-iodoperfluoroalkylated products (I-(CH2)2CH=C(R)-CH2-RF) are obtained in high yields. Isocyanides (R-NC), as C-N unsaturated compounds, also undergo the xenon-lamp-irradiated iodoperfluoroalkylation to provide the corresponding 1,1-adducts (R-N=C(I)-RF) in good yields. Furthermore, the present photoinitiation procedure can be applied to the iodotrifluoromethylation of unsaturated compounds, when the xenon-lamp-irradiated reactions are conducted under the refluxing conditions of excess CF3-I. 相似文献
614.
Banskota AH Tezuka Y Tran KQ Tanaka K Saiki I Kadota S 《Chemical & pharmaceutical bulletin》2000,48(4):496-504
From the MeOH extract of leaves of Combretum quadrangulare, fifteen new cycloartane-type triterpenes, methyl quadrangularates A-D (1-4) and N-P (8, 6, 12), methyl 24-epiquadrangularate C (5), quadrangularic acid E (9), 23-deoxojessic acid (10), 1-O-acetyl-23-deoxojessic acid (11), quadragularols A (7) and B (13) and norquadrangularic acids B (14) and C (15) were isolated together with two known cycloartane-type triterpenes, methyl 23-deoxojessate (16) and 4beta,14alpha-dimethyl-5alpha-ergosta-9beta++ +,19-cyclo-24(31)-en-3beta-hydroxy-4alpha-carboxylic acid (17). Betulinic acid (18), beta-sitosterol (19), kamatakenin (20), isokaempferide (21), 5,7,4'-trihydroxy-3,3'-dimethoxyflavone (22) and 5,4'-dihydroxy-3,7,3'-trimethoxyflavone (23) were also obtained from the same extract. The structures of the new compounds were elucidated on the basis of spectral analysis and chemical conversions. All the isolated compounds were tested for their cytotoxicity towards highly liver metastatic murine colon 26-L5 carcinoma cells, and the cycloartane-type triterpenes showed various degrees of cytotoxicity, whereas all the flavonoids possessed strong cytotoxicity with ED50 values equal to or less than 6 microM. 相似文献
615.
Kazuhisa Yoshimura Hiroyuki Kaji Eishi Yamaguchi Toshikazu Tarutani 《Analytica chimica acta》1981,130(2):345-352
Vanadium(V) ions are strongly adsorbed on Sephadex G-25 gel at pH 4.2, and are desorbed reversibly into 0.1 M acids. Vanadium present in rocks and in natural waters at μg l−1 levels can be separated and concentrated by means of a gel column at pH 6 (in order to avoid the interference of molybdenum(VI)) and determined spectrophotometrically with 4-(2-pyridylazo)resorcinol. Interference by iron(III) can be suppressed by adding copper(II)—CyDTA. Large amounts of sodium chloride and potassium nitrate have little effect on the adsorption. 相似文献
616.
Kazuhiro Hayasaka Toshikazu Ohtsuka Haruhisa Shirahama Takeshi Matsumoto 《Tetrahedron letters》1985,26(7):873-876
Africanol, which had been previously derived from humulene, was converted to dactylol through a formal 1,2-shift of a methyl group, which involved a cyclopropane sliding reaction and subsequent cyclopropane ring opening. 相似文献
617.
Reactions of several cyclic disulfides with carbenes generated by catalytic and photochemical decompositions of diazo compounds have been studied. Carbenes reacted with cyclic disulfides yielding 1,3-dithiane quantitatively as S-S insertion reaction, while the selective desulfurization results in the reaction of disulfides with bulky substituents. The carbene reaction is sensitive to bulkiness of disulfides. 相似文献
618.
Toshikazu Kawaguchi Dhesingh Ravi Shankaran S.J. Kim Kiyoshi Matsumoto Norio Miura 《Talanta》2007,72(2):554-560
We have developed a new immunosensor based on self-assembly chemistry for highly sensitive and label-free detection of 2,4,6-trinitrotoluene (TNT) using surface plasmon resonance (SPR). A monolayer of amine terminated poly(ethylene glycol) hydrazinehydrochloride (PEG-NH2) thiolate was constructed on an activated gold surface and immobilized with trinitrophenyl-β-alanine (TNPh-β-alanine) by amide coupling method. The binding interaction of a monoclonal anti-TNT Ab (M-TNT Ab) with TNPh-β-alanine immobilized thiolate monolayer surface was monitored and evaluated for detection of TNT based on the principle of indirect competitive immunoreaction. Here, the competition between the self-assembled TNT derivative and the TNT in solution for binding with antibody yields in the response signal that is inversely proportional to the concentration of TNT in the linear detection range. With the present immunoassay format, TNT could be detected in the concentration range from 0.008 ng/ml (8 ppt) to 30 ng/ml (30 ppb). The response time for an immunoreaction was 2 min and one immunocycle could be done with in 4 min including surface regeneration. Bound antibodies could be easily eluted from the self-assembled immunosurface at high recoveries (more than 100 cycles) using pepsin solution without any damage to the TNT derivatives immobilized on the surface. The compact self-assembled monolayer was highly stable and prevented the non-specific adsorption of proteins on the surface favoring error free measurement. 相似文献
619.
A convergent synthesis of the FGHI ring segment of yessotoxin was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis. 相似文献
620.
Susumu Tajima Tadashige Azami Haruo Shizuka Toshikazu Tsuchiya 《Journal of mass spectrometry : JMS》1979,14(9):499-502
Single and double hydrogen atom transfers in reactions (1) and (2) in the mass spectra of ethyl benzoate, isopropyl benzoate, and isobutyl benzoate have been investigated with reference to the ortho effect: (1) [C6H5CO2R]+? → [C6H5CO2H]+? (m/z 122) + (R-H); (2) [C6H5CO2R]+? → [C6H5CO2H2]+ (m/z 123) + · (R-2H). It is demonstrated that the intermediate ion [C6H5CO2H2]+ has the protonated benzoic acid structure with the hydrogen atom on the carbonyl group. 相似文献