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71.
Shinsaku Fujita 《Journal of mathematical chemistry》2007,42(2):215-263
The concepts of double coset representations and sphericities of double cosets are proposed to characterize stereoisomerism, where double cosets are classified into three types, i.e., homospheric double cosets, enantiospheric double cosets, or hemispheric double cosets. They determine modes of substitutions (i.e., chirality fittingness), where homospheric double cosets permit
achiral ligands only; enantiospheric ones permit achiral ligands or enantiomeric pairs; and hemispheric ones permit achiral
and chiral ligands. The sphericities of double cosets are linked to the sphericities of cycles which are ascribed to right
coset representations. Thus, each cycle is assigned to the corresponding sphericity index (a
d
, c
d
, or b
d
) so as to construct a cycle indices with chirality fittingness (CI-CFs). The resulting CI-CFs are proved to be identical
with CI-CFs introduced in Fujita’s proligand method (S. Fujita, Theor. Chem. Acc. 113 (2005) 73–79 and 80–86). The versatility
of the CI-CFs in combinatorial enumeration of stereoisomers is demonstrated by using methane derivatives as examples, where
the numbers of achiral plus chiral stereoisomers, those of achiral stereoisomers, and those of chiral stereoisomers are calculated
separately by means of respective generating functions. 相似文献
72.
Tetsuro Fujita 《中国化学快报》2007,18(2):175-177
A new highly conjugated alkaloid of veratramine type, 225,25S,5α-veratramine-7(8),12(14)-diene-3β,13β,23β-triol-6-one (1), was isolated from the bulbs of Fritillaria hupehensis Hsiao et K.C. Hsia. Its structure was determined on the basis of spectroscopic evidences. 相似文献
73.
ESTIMATION OF AN INDEX OF HYDROPHOBICITY OF DNA INTERIOR USING 5-METHOXYPSORALEN AS A FLUORESCENT PROBE 总被引:1,自引:0,他引:1
Masako Sasaki Isao Nakasato Hiroyuki Sugiura Hitoshi Fujita Toshibumi Sakata 《Photochemistry and photobiology》1987,46(4):551-555
The index of hydrophobicity of DNA interior was estimated by measuring fluorescence spectra of psoralen derivatives associated with DNA. The environment around 5-MOP associated with DNA was as hydrophobic (Dk = 34) as methanol, suggesting that the molecules reside at the space between the base-pairs in B-form DNA. This is also true for 8-MOP. Thus, planar and aromatic molecules of 5- and 8-MOP are more stable in the interior of DNA than in aqueous medium due to hydrophobic affinity. 相似文献
74.
Position — Sensitive single-wire proportional counter for conversion electron Mössbauer spectroscopy
A position-sensitive single-wire proportional counter for the INS 2 air-core spectrometer has been improved to take conversion electron Mössbauer spectrum as a function of electron energy with a multichannel mode. The position resolution at 13.6 keV was found to become 1.6 mm with the counter gas pressure of 320 Torr. The position resolution was obtained as a function of energy between 7 and 60 keV for gas pressure of 40 Torr, 160 Torr and 320 Torr. The L, M and N conversion electron spectrum of the 14.4 keV transition in57Fe was taken with the present system. Overall momentum resolution was found to be 0.23% for the L1-line and 0.19% for the M1 line. 相似文献
75.
In bacteriorhodopsin (bR), Arg-82bR has been proven to be a very important residue for functional role of this light-driven proton pump. The arginine residue at this position is a super-conserved residue among archaeal rhodopsins. pharaonis phoborhodopsin (ppR; or called as "pharaonis sensory rhodopsin II") has its absorption maximum at 498 nm and acts as a sensor in the membrane of Natronobacterium pharaonis, mediating the negative phototaxis from the light of wavelength shorter than 520 nm. To investigate the role of the arginine residue (Arg-72ppR) of ppR corresponding to Arg-82bR, mutants whose Arg-72ppR was replaced by alanine (R72A), lysine (R72K), glutamine (R72Q) and serine (R72S) were prepared. These mutants were unstable in low concentrations of NaCl and lost their color gradually when the proteins were solubilized with 0.1% n-dodecyl-beta-D-maltoside. The order of instability was R72S > R72A > R72K > R72Q > the wild type. The rates of denaturation were reduced in a solution of high concentrations of monovalent anions. 相似文献
76.
Hiroto Tachikawa Hiroshi Kawabata Kazumi Matsushige 《Journal of organometallic chemistry》2005,690(12):2895-2904
The structures and electronic states of phenyl-capped terthiophene (denoted by P3T) and the ionic species of P3T have been investigated by means of density functional theory (DFT) and direct MO dynamics calculations. P3T is one of the high-performance molecular devices, which has been utilized as a semi-conductor. The calculations indicated that the neutral P3T has a non-planar structure whose the phenyl rings in both ends of thiophene chain are largely deviated from the molecular plane. The cation and anion radicals, dication and dianion were considered as its ionic states. The structure for cation radical of P3T is close to more planar than that of neutral P3T. The structures for anion radical, dication and dianion take a pure planar structure. The first excitation energy of neutral P3T is calculated to be 2.90 eV at the TD-B3LYP/6-31G(d)//B3LYP/6-311+G(d) level, while the P3T cation and anion radicals have lower excitation energies (1.22 and 1.10 eV, respectively). The direct MO dynamics calculation showed that neutral, cation and anion hold near planar structure at 300 K. On the other hand, oligothiophene (n = 5) and its ionic species are strongly deformed from the planar structure, and thiophene rings in both ends of chain rotate rapidly by thermal activation. The mechanism of the electron conductivity in P3T was discussed on the basis of theoretical results. 相似文献
77.
Cs2CO3 was found to efficiently catalyze the reaction of β-cyclodextrin and N-tosylimidazole. Stirring β-cyclodextrin and N-tosylimidazole in 1/1.2 molar ratio in DMF in the presence of catalytic amount of Cs2CO3 at rt for 1.5 h afforded 2A-mono(O-tosyl)-β-cyclodextrin in 32% yield. The 2A,2B-, 2A,2C- and 2A,2D-ditosylates were isolated in ca. 6-7% yields, respectively, when β-cyclodextrin and N-tosylimidazole were used in 1/2.5 molar ratio. The charge of excess (10 equiv) of N-tosylimidazole ensured a one-step direct (protection-free) synthesis of the per(2-O-tosyl)-β-cyclodextrin in 5% isolated yield. N-(m-Nitrobenzenesulfonyl)imidazole even allowed a much faster access to the corresponding persulfonate in only 1 h reaction. 相似文献
78.
A mixed-valence state of the cation radical tetrathiafulvalene dimer, [(TTF)2]+*, is generated by the electrochemical oxidation of a stacked TTF dimer accommodated within an organic-pillared coordination cage. This mixed-valence species is remarkably stable (t1/2 = approximately 1 day at room temperature in aqueous solution under air) and clearly characterized by cyclic voltammogram and electronic absorption spectroscopy. 相似文献
79.
80.
Hiroyuki Ishibashi Hajime Komatsu Kazumi Maruyama Masazumi Ikeda 《Tetrahedron letters》1985,26(47):5791-5794
A Pummerer rearrangement product, 4-chlorophenylthiomethyl trifluoroacetate (6), obtained from 4-chlorophenyl methyl sulfoxide (5) and trifluoroacetic anhydride, reacted with 1-alkenes in trifluoroacetic acid to give the ene products 8, which were readily converted into the terminal 1,3-dienes 10 by oxidation and subsequent pyrolysis. Using this method, 9,11-dodecadien-1-yl acetate (12), a sex pheromone of the red bollworm moth, was synthesized. 相似文献