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41.
42.
Proton T1 measurement with the Fourier transform method combined with quenching of dipolar coupling through selective deuterium substitution is shown to be a useful method for elucidating intra- and intermolecular interactions in solution, with 2′,3′-isopropylideneadenosine as an example. Average distances between H-8 and ribose protons are determine in combination with carbon-13 T1 measurement. The method is compared with the nuclear Overhauser effect. 相似文献
43.
44.
Yasuhide Yukawa Hisao Morisaki Kiyoshi Tsuji Seung-Geon Kim Takashi Ando 《Tetrahedron letters》1981,22(51):5187-5190
The behavior of ion pairs in the trifluoroacetolysis of 2-arylethyl arenesulfonates was studied by means of tracer techniques with deuterium and oxygen-18. 相似文献
45.
Akira Ando 《Journal of fluorine chemistry》2005,126(5):765-770
Treatment of 2-chloro-3,3-difluoroprop-2-en-1-ol derivatives (2) with methanesulfonyl chloride in the presence of a base did not give the expected esters but 2-chloro-1,1-difluoroprop-2-enyl methanesulfonates (4) through a novel [3,3] sigmatropic rearrangement. Reaction of 4 with diethylzinc in the presence of tetrakis(triphenylphosphine) palladium gave 1-alkyl- or 1-aryl-2-chloro-3-fluoropenta-1,3-dienes in moderate to good yields through a CC bond formation followed by dehydrofluorination. 相似文献
46.
J Holinej H Y Ando J W Snow 《Journal of chemical information and computer sciences》1989,29(4):233-236
Buffer changes and certain drugs cause temperature shifts, amplitude changes, and transition broadening in the differential scanning calorimetric (DSC) analysis of erythrocyte membranes. However, it has been difficult to interpret and quantitate these shifts and changes because the scans are composed of multiple overlapping transitions and because more than one transition may be simultaneously affected. An empirical approach has been developed by using Gaussian modeling to resolve these calorimetric transitions. Data analysis was carried out on a microcomputer using a nonlinear regression program (PCNONLIN) to fit the data scans. These results show that changes in the calorimetric scans of erythrocyte membranes due to alterations in the buffer environment, such as pH and osmolarity, can be resolved by fitting the data scans with the proposed mathematical model and optimizing the resolution parameters with PCNONLIN. In addition, resolution uncovered hidden characteristics that may not have been readily evident. Under certain conditions, for example, apparent transition shifts were shown to actually be amplitude changes and transition broadening. Determination of the limitations and validity of this method was accomplished with simulation studies. This technique offers a simple means for fitting overlapping DSC transitions by use of a commercially available nonlinear regression program that can be run on a microcomputer. 相似文献
47.
The most widely used method for qualitative and quantitative analysis of carbonyl compounds is the 2,4-dinitrophenylhydrazine method through the formation of 2,4-dinitrophenylhydrazone derivatives. However, this method may cause an analytical error because 2,4-dinitrophenylhydrazones have both E- and Z-stereoisomers. Purified aldehyde-2,4-dinitrophenylhydrazone demonstrated only the E-isomer. However under UV irradiation and the addition of acid, both E- and Z-isomers were seen. The spectral patterns of Z-isomers were different from those of E-isomers and the absorption maximum wavelengths were shifted towards shorter wavelengths by 5-8 nm. An equilibrium Z/E isomer ratio was observed in 0.02-0.2% (v/v) phosphoric acid solutions. In the case of acetaldehyde- and propanal-2,4-dinitrophenylhydrazones, the equilibrium Z/E isomer ratios were 0.32 and 0.14, respectively. However, when irradiated with ultraviolet light at 364 nm, the isomer ratios were increased beyond this constant ratio and reached 0.55 and 0.33, respectively. Zero-order rates for decreases of aldehyde derivatives were observed under UV irradiation (364 nm), however the decreases of concentration were not observed in phosphoric acid solutions. The best method for the determination of aldehyde-2,4-dinitrophenylhydrazones by HPLC is to add phosphoric acid to both the sample and the standard solution, to form a 0.02-1% acid solution. 相似文献
48.
Silylcarbenes are generated by the pyrolysis of 1,1-bis(trimethylsilyl)-1-alkanols with elimination of trimethylsilanol. 相似文献
49.
[reaction: see text] Chiral C(4)-substituted (E)- or (Z)-1-alkynyl-1-trimethylsilyloxy-2-butene systems provide anti-(Z) or syn-(Z) conjugated dienyne, with a very high level of stereocontrol, on treatment with BF(3).OEt(2) in CH(2)Cl(2) at -50 degrees C in the presence of allyltrimethylsilane. The Cieplak conformation for (E)-substrates and neighboring-group participation for (Z)-substrates are considered to be responsible for the stereochemical consequences. 相似文献
50.
Rotational correlation times (τT) of the 5′-AMP molecule deduced from spin-lattice relaxation times (T1) of different protons in the molecule agree fairly well with each other in the temperature range of 3.5–74°C. The same is true with τT values deduced from 13CT1 values. These results indicate that the internal motions are slow as compared to the overall rotation of the 5′-AMP molecule. 相似文献