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51.
Kita Y Iio K Kawaguchi K Fukuda N Takeda Y Ueno H Okunaka R Higuchi K Tsujino T Fujioka H Akai S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(21):3897-3905
A linear approach to the total synthesis of racemic fredericamycin A (1) through the oxidative intramolecular [4 + 2] cycloaddition of a (phenylthio)acetylene-cobalt complex is described, which is applicable for the asymmetric total synthesis of naturally occuring 1. The highlight of this work is the aromatic Pummerer-type reaction with 1-ethoxyvinyl chloroacetate, which effects the introduction of the oxygen functional group to the internal B-ring of the highly functionalized, congested polyaromatic ABC-ring moiety. 相似文献
52.
Native DL-pantothenic acid, having a 1,3-diol structure, was chirally resolved by ligand exchange capillary electrophoresis using (S)-3-amino-1,2-propanediol as a chiral selector and the borate anion as a central ion. The optimum conditions for both high resolution and short migration time of DL-pantothenic acid were found to be 200 mM (S)-3-amino-1,2-propanediol and 200 mM borate buffer (pH 9.2) containing 15% methanol with an applied voltage of +25 kV at 20 degrees C, using direct detection at 200 nm. With this system, the resolution (Rs) of racemic pantothenic acid was approximately 1.7. When (S)-1,2-propanediol, (S)-1,2,3-propanetriol, (S)-1,3-butanediol or (S)-1-amino-2-propanol were used as chiral ligand instead of (S)-3-amino-1,2-propanediol, DL-pantothenic acid was not enantioseparated. When borate was replaced with Tris or butylborate, no chiral separation was achieved. Therefore, the ionic interaction between the amino and carboxyl groups of the ternary complex may play an important role in the enantioseparation of DL-pantothenic acid by the proposed CE system. 相似文献
53.
A capillary electrophoresis-mass spectrometry method for the simultaneous chiral determination of enantiomers of methamphetamine (MA), amphetamine (AP), dimethylamphetamine (DMA) and p-hydroxymethamphetamine (pOHMA), in urine has been developed. The internal standards used were 2-phenylethylamine and 1-amino4-phenylbutane. The electrolyte was 1 M formic acid (pH 2.2). The chiral selector, which was added to the electrolyte, was a mixture of 3 mM beta-cyclodextrin and 10 mM heptakis(2,6-di-O-methyl)-beta-cyclodextrin. The detection limits were 0.03 microg ml(-1) for the enantiomers of MA and AP and 0.05 microg ml(-1) for the enantiomers of pOHMA using selected ion monitoring. In the analysis of healthy adult urine samples spiked with MA, AP and pOHMA, the precision of within-run assays (n = 4) for the migration time after correction with two internal standards were under 0.04%, and the detection yields utilizing solid phase extraction were 95-105%. This method was applicable to the analysis of urine samples of MA addicts and DMA addicts. 相似文献
54.
The cyclization of 2-(3′,4′-dimethyl6?′-trimethylsilyl-4′-hexenyl)-2-cyclohexenone with TiCl4, afforded stereospecifically 6α,7α-dimethyl-6β-vinyl-5βH-1-decalone derivative and the two-fold diastereoselection involved is reasoned in terms of orientation control and folding strain control. 相似文献
55.
Yamanaka K. Nishiwaki Y. Iio K. Kato T. Mitsui T. Tojo T. Atake T. 《Journal of Thermal Analysis and Calorimetry》2002,70(2):371-378
The complex phase transitions involving dielectricity and magnetism on distorted triangular lattice antiferromagnets, "KNiCl3-family" crystals, which have the crystal structures derived from the prototype CsNiCl3, were studied through the heat capacity measurements. These crystals are classified into characteristic three groups from
the viewpoint of magnetic and structural properties clarified so far. The results of the dielectric constant measurement as
a function of temperature are also presented in detail. The present calorimetric study reveaed that the structural successive
phase transitions rather than the magnetic transitions in these crystals are recognized more distinctly as the presence of
specific heat anomalies at the respective phase transition points.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
N Yui Y Akiyama T Matsumoto T Iinuma T Ishikawa T Nakajima K Machida J Nishikawa M Iio K Uno 《Radioisotopes》1988,37(11):608-614
Prospective study of bone scintigraphy was performed on 414 patients with breast carcinoma and 88 patients with prostate carcinoma. In 468 of them, confirmative diagnoses of bone, whether metastasis was existent or not, were made after the observations over a year. Finally, the incidences of bone metastasis were 11 percent for breast carcinoma and 54 percent for prostate carcinoma respectively. The efficacy of preoperative bone scintigraphy in breast carcinoma was comparable to that in prostate carcinoma with regard to improvement of predictive probability of bone metastasis: raising up the probability in the positive cases and bringing down in the negative cases. 相似文献
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58.
The aromatic segment of rifamycin S () was synthesized from the cyclohexadienone or in high overall yield. 相似文献
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