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41.
Hidetsura Cho Yoshiko Ohnaka Mariko Hayashimatsu Masaru Ueda Keiyuu Shima 《Tetrahedron letters》1986,27(52):6377-6380
Chlorination of 5,6-dihydropyrimidine-4-(3H)-one derivatives (1) with POCl3 gave 1,4(3,4)-dihydropyrimidines (3), whose alkoxycarbonylation (ClCOOREt3N or NaH) afforded regioselectively novel compounds (4). A new Pummerer
rearrangement of compound (1, X=
---S(O)CH3) with
3, gave compound (5h). 相似文献
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The INDO calculations were performed on bicyclo[2.1.1]hex-5-yl radical. From these calculations, it was confirmed that the hyperfine coupling constants depend largely on the geometry of the α hydrogen. The localized MO's were obtained from the canonical MO's calculated by using the INDO method. With the use of the localized MO's thus obtained, the variation in the hyperfine coupling constants at the 6exo- and 6endo-protons in this radical was explained in terms of the through-bond and/or the through-space interactions according to the procedure which we proposed previously. That is by the procedure we can selectively pick up a particular interaction between the specified localized MO's. The hyperfine coupling constant in this radical can be expressed by the summation of several interaction terms. The difference in the hyperfine spin coupling constants of the H6exo and H6endo in the radical now concerned has been attempted to explain using MO coefficients of the occupied orbitals. 相似文献
44.
Masaru Kihara Kouichi Yoshioka Tamboue Deffo Dwight S. Fullerton Douglas C. Rohrer 《Tetrahedron》1984,40(7):1121-1133
Earlier studies have shown that the β-D-digitoxose (2,6-dideoxy-β-D-mannopyranose) directly attached to the cardiac glycoside steroid C3 has the greatest effect on biological activity. This report describes the synthesis of eight digitoxosides (2a-9a), with widely varying cyclic and acyclic C17β-side groups, and the corresponding C3',C4'-acetonides (2b-9b). NMR analysis of conformational strain introduced by the acetonide groups is supported by crystallographic analysis of the sugars' torsion angles. 相似文献
45.
Kazunori Matsui Takayuki Kaneko Yasunori Yaginuma Masaru Ryu 《Journal of Sol-Gel Science and Technology》1997,9(3):273-277
A spin probe TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy) was dissolved in a tetraethyl orthosilicate sol-gel reaction
system and measured by electron spin resonance spectroscopy at 295 K. The nitrogen hyperfine coupling constant was from 1.64–1.66
mT in the sol-gel solutions. The values were sensitive to the ethanol-to-water ratio of the solutions. The hyperfine coupling
constant in the xerogels was 1.70 mT, which was almost the same as that in water, indicating that the probe molecules were
trapped in silica pores with water adsorbed on the silica surfaces. The motion of TEMPOL in the xerogels was considerably
slower than in the sol-gel solutions. The local viscosity estimated was from 70–90 cP. The ESR spectra of TEMPOL were altered
during the sol-gel process, indicating that adsorbed water on the silicas surfaces has an important role for trapping organic
molecules in sol-gel glasses. 相似文献
46.
Masaru Kawakami Katherine Byrne Bhavin S Khatri Tom C B McLeish D Alastair Smith 《Chemphyschem》2006,7(8):1710-1716
The viscoelastic properties of single poly(ethylene glycol) (PEG) molecules were measured by analysis of thermally and magnetically driven oscillations of an atomic force microscope (AFM) cantilever/molecule system. The molecular and monomer stiffness and friction of the PEG polymer were derived using a simple harmonic oscillator (SHO) model. Excellent agreement between the values of these two parameters obtained by the two approaches indicates the validity of the SHO model under the experimental regimes and the excellent reproducibility of the techniques. A sharp minimum in the monomeric friction is seen at around 180 pN applied force which we propose is due to a force induced change in the shape of the energy landscape describing the conformational transition of PEG from a helical to a planar state, which in turn affects the timescale of the transition and therefore modifies the measured internal friction. A knowledge of the viscoelastic response of PEG monomers is particularly important since PEG is widely used as a linker molecule for tethering groups of interest to the AFM tip in force spectroscopy experiments, and we show here that care must be exercised because of the force-dependent viscoelastic properties of these linkers. 相似文献
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