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61.
The present efficient synthesis of [5'-13C]ribonucleosides and 2'-deoxy[5'-13C]ribonucleosides is characterized by the synthesis of the D-[5-13C]ribose derivative as an intermediate via the Wittig reaction of 4-aldehydo-D-erythrose dialkyl acetals with Ph3P13CH3I-BuLi to introduce the 13C label at the 5-position of a pentose. This was followed by the highly diastereoselective osmium dihydroxylation for the preparation of 2,3-di-O-benzyl-D-[5-13C]ribose dialkyl acetal and the cyclization from D-[5-13C]ribose dialkyl acetal derivatives to the alkyl D-[5-13C]ribofuranoside derivative by the use of LiBF(4). The obtained D-[5-13C]ribose derivative was converted into [5'-13C]ribonucleosides and subsequently into the corresponding 2'-deoxynucleosides. 相似文献
62.
Kaoru Suzuki Iwao Nishiyama Yasushi Ozaki Kozo Kuchitsu 《Chemical physics letters》1978,58(1):145-148
Light emission from Cl(5p) atoms (near 440 nm) produced in the reaction of HCl in a discharged flow of argon was investigated with a flowing-afterglow apparatus. Ionic species, most probably argon ions in metastable states, Ar+M, were found to be responsible for the Cl(5p) production in the dissociative excitation of HCl. 相似文献
63.
Tatsuya Oshima Kaoru Oishi Keisuke Ohto Katsutoshi Inoue 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):79-85
Extraction behaviors of catecholamines with a series of calixarene carboxylic acid derivatives were investigated. Relatively large calix[6]arene and calix[8]arene extract catecholamines into the organic solution, while smaller calix[4]arene and the monomer analog do not. The calix[6]arene, which has a cavity that fits a protonated amino group well, selectively extracts a primary amino compound dopamine over other catecholamines. Slope analysis and Job’s method confirmed formation of a 1:1 complex between the calix[6]arene and dopamine. On the other hand, the calix[8]arene extracts both dopamine and adrenaline, due to the large cavity for induced-fit recognition. Dopamine extracted with the calixarene is quantitatively stripped by contacting the organic solution with a fresh acidic solution. 相似文献
64.
Since the physical properties of lithium borate glasses xLi2O-(1-x)B2O3 (0<x< 0.28) vary over a wide range with the composition, this binary system is particularly suitable for studying the relationship
between vibrational anharmonicity and fragility. The density, the linear expansion coefficient, the longitudinal and transverse
ultrasonic velocities and their respective temperature coefficients of the velocities are measured, from which the vibrational
anharmonicity in lithium borate glasses is evaluated with the help of the Grüneisen parameter at the Debye cut-off frequency
and the Anderson-Grüneisen parameter: these two parameters plotted vs. composition have the same characteristics with minima at x≈0.08. The fragility is evaluated from the temperature width of the glass transition; the fragility also shows a minimum at
x≈0.08. The presence of minima at x≈0.08 is ascribable to the fact that the crosslinking density between six-membered rings in the glass reaches a maximum at
this composition. We show that the anharmonic parameters strongly correlate with the fragility metrics.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
65.
K Maruyama T Yuda A Okamoto C Ishikura S Kojima M Iwatsuru 《Chemical & pharmaceutical bulletin》1991,39(6):1620-1622
The effect in mice of the molecular weight of polyethyleneglycol on prolonging the circulation time of large unilamellar liposomes (LUVs) was examined using four different distearoyl N-(monomethoxy polyethyleneglycol succinyl) phosphatidylethanolamines (DSPE-PEGs). The molecular weights tested were 1000, 2000, 5000 and 12000. Incorporation of 6 mol% of DSPE-PEG in LUV composed of distearoylphosphatidylcholine (DSPC) / cholesterol (CH) (1:1 in molar ratio) increased the blood circulation half-life significantly more than those without DSPE-PEG derivatives. DSPE-PEGs with molecular weights of 1000 and 2000 prolonged the circulation time of liposomes more than other DSPE-PEGs with higher molecular weights, such as 5000 and 12000. Their effects are also higher than ganglioside GM1, a well described glycolipid with this effect. DSPC/CH LUV-incorporated DSPE-PEG with a molecular weight of 2000 displayed a high concentration in the blood, approximately 40% of the dose, 6 h after the injection. 相似文献
66.
Hiroto Nagaoka Kaoru Kobayashi Toshiaki Okamura Yasuji Yamada 《Tetrahedron letters》1987,28(52):6641-6644
The sequential Michael reaction of (S)-4,5-di-O-isopropylidenepent-2- enoate
and
with lithium enolate
afforded diastereo- and enantioselectively bicyclo[2.2.2]octane
and
(or
), respectively. The adducts were efficiently converted into both enantiomeric keto aldehydes (−)-
and (+)-
. 相似文献
67.
68.
Yamaguchi T Sunatsuki Y Kojima M Akashi H Tsuchimoto M Re N Osa S Matsumoto N 《Chemical communications (Cambridge, England)》2004,(9):1048-1049
Dinuclear [(NiL)Gd(hfac)(2)(EtOH)](H(3)L = 1,1,1-tris(N-salicylideneaminomethyl)ethane, Hhfac = hexafluoroacetylacetone), trinuclear [(NiL)(2)Gd(NO(3))], and tetranuclear [(NiL)Gd(CH(3)CO(2))(2)(MeOH)](2) complexes, were prepared by treating [Ni(HL)] with [Gd(hfac)(3)(H(2)O)(2)], Gd(NO(3))(3).6H(2)O, and Gd(CH(3)CO(2))(3).4H(2)O, respectively, in the presence of Et(3)N. All the complexes show that ferromagnetic interactions occur between the Ni(II) and Gd(III) ions. 相似文献
69.
T Takahashi N Kakuhara S Katsuragawa Y Kojima A Hirose T Nakasato K Yoshioka K Kato T Yanagisawa 《Radioisotopes》1987,36(10):519-522
Patients with diffuse increased accumulation in both kidneys on 99mTc-MDP bone scintigram were evaluated quantitatively. Among 1,100 cases, 7 (0.63%) showed this finding. The accumulation density ratios of kidneys/lumbal vertebra in A/D exchanged images of these patients were compared with control group, so that these ratios of patient group were higher than control group statistically. In conclusion, the accumulation density ratio was made the index of diffuse increase accumulation in both kidneys on 99mTc-MDP bone scintigram. 相似文献
70.
Masaru Kojima 《Tetrahedron letters》2007,48(25):4431-4436
A new fluorous benzylidene acetal protecting group was regioselectively introduced into carbohydrates, deprotected under acidic conditions, and reused. Oligosaccharides were synthesized via regioselective conversion of the fluorous acetal group to the benzyl group by traditional reaction conditions. The fluorous compounds were easily separated from non-fluorous by-products by fluorous solid phase extraction. 相似文献