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21.
The antitumor activity of (1----3)-beta-D-glucans was tested in order to clarify its conformation-dependent response together with conformational elucidation by carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy. It was shown that the following three conformations, single chain, single helix and triple helix, are readily distinguished by the high-resolution solid-state 13C-NMR method. It turned out that preparations of linear (1----3)-beta-D-glucans of a triple helical conformation were ineffective in the inhibition of tumor growth. These linear (1----3)-beta-D-glucans were converted to an effective form in the inhibition of tumor growth when they were lyophilized from dimethyl sulfoxide (DMSO) solutions as a result of a conformational change from the triple helical to the single chain forms. They were not effective, however, when assayed in DMSO solution. In contrast, it was found that a branched (1----3)-beta-D-glucan is effective not only in either saline solutions of the triple helical sample or the lyophilized sample from DMSO, but also in DMSO solution. The aforementioned drastic change in antitumor activity was interpreted in terms of resulting conformational changes as analyzed by the 13C-NMR method. 相似文献
22.
The title 9-borabicyclo[3.3.1]nonane(9-BBN) ate complex (1) brings about selective removal of tertiary alkyl, benzyl and allyl halides to give the corresponding hydrocarbons in excellent yields without concomitant attack on secondary, primary and aryl derivatives. The reduction of cis- and trans - 4 - t - butyl - 1 - methylcyclohexyl chlorides (2) with 1 gives 4 - t - butyl - 1 - methylcyclohexanes (3) with partial inversion of configuration in cyclohexane, while that in benzene gives thermodynamically stable trans-3 predominantly. The reactions of 1,1 - dimethyl - 5 - hexenyl chloride (4) and 1,7,7 - trimethylbicyclo[2.2.1]hept - 2 - yl chloride (8) with 1 proceed with the rearrangements characteristic to a carbonium ion intermediate. The reduction of 1 - ethyl - 1 - methylpentyl chloride with 1 follows a second-order rate equation. 相似文献
23.
Itoh T Nagata K Yokoya M Miyazaki M Kameoka K Nakamura S Ohsawa A 《Chemical & pharmaceutical bulletin》2003,51(8):951-955
Chiral 1-substituted isoquinoline derivatives, which were obtained by the reaction using alanine derivatives as chiral auxiliaries, were transformed to (S)-2,3,9,10,11-pentamethoxyhomoprotoberberine (7) and a synthetic intermediate for O-methylkreysigine (9) in good yields and high stereoselectivity. The corresponding chiral allyl derivative of isoquinoline was transformed to a pyrrolidinoisoquinoline (16) in a highly enantioselective manner. 相似文献
24.
Akio Okamoto Eiichi Watanabe Itaru Mita 《Journal of polymer science. Part A, Polymer chemistry》1979,17(8):2483-2490
The deactivation of α-methylstyryl and styryl carbanions followed by spectral change and titration was studied kinetically. First-order rate constants were obtained for the deactivation of oligo-α-methylstyryl lithium, disodium, and dipotassium in tetrahydrofuran and of polystyryl potassium in varying degrees of polymerization in benzene that contained a small amount of tetrahydrofuran and n-hexane. It was observed that the addition of cryptate [222] exerts a significant effect on the system of oligo-α-methylstyryl disodium in tetrahydrofuran. The effect of dilution, degree of polymerization of the polymer, and counterions on the rate of deactivation of carbanions was discussed. 相似文献
25.
The purpose of this study is to examine whether molecular dynamics (MD) simulations using a commercially available software for personal computers can estimate the glass transition temperature (Tg) of amorphous systems containing pharmaceutically-relevant excipients. MD simulations were carried out with an amorphous matrix model constructed from isomaltoheptaose, and the Tg estimated from the calculated density versus temperature profile was compared with the Tg measured by differential scanning calorimetry (DSC) for freeze-dried isomalto-oligomer having an average molecular weight close to that of isomaltoheptaose. The Tg values determined by DSC were lower by 10 to 20 K than those extrapolated from the Tg values estimated by MD simulation. Fragility parameter was estimated to be 56 and 51 from MD simulation and from DSC measurement, respectively. Thus, the results suggest that MD simulation can provide approximate estimates for the Tg and fragility parameter of amorphous formulations. However, a reduction of the cooling rate, achievable by sufficiently elongating the simulation duration, is necessary for more accurate estimation. 相似文献
26.
Kazuyuki MiyashitaHidenobu Murafuji Hiroshi IwakiEito Yoshioka Takeshi Imanishi 《Tetrahedron》2003,59(26):4873-4879
As a second-generation pyridoxal model compound for cystathionine β-synthase, we designed a novel model compound having an ionophore function and an imidazole function, application of which to the β-replacement reaction with various thiols smoothly took place to give S-substituted cysteines. Peptides having a serine-O-carbonate residue at the N-terminal position were also converted to the corresponding peptides having an S-substituted cysteine residue under the catalytic conditions of the novel pyridoxal model compound. 相似文献
27.
Itoh F Yoshioka Y Yukishige K Yoshida S Ootsu K Akimoto H 《Chemical & pharmaceutical bulletin》2000,48(9):1270-1280
The glutamic acid moiety of N-[4-[3-(2,4-diamino-7H-pyrrolo[2,3-d]pyrimidin-5-yl)propyl]benzoyl]-L-g lutamic acid (1b, TNP-351) and the related compound (1a), was replaced with various N(omega)-acyl-, sulfonyl-, carbamoyl- and aryl-2,omega-diaminoalkanoic acids, and the inhibitory effects of the resulting products (9, 11, 14, 18, 21, 23, 25, 30, 36) on dihydrofolate reductase (DHFR), the growth of murine fibrosarcoma Meth A cells, and methotrexate-resistant human CCRF-CEM cells, were examined. Compounds (9a-f) acylated with a hemiphthaloyl group were efficiently synthesized by coupling pyrrolo[2,3-d]pyrimidine carboxylic acids (7a,b) and N(omega)-phthaloyl 2,omega-diaminoalkanoic acid methyl esters (6a-c) and subsequent hydrolysis. The other N(omega)-acyl- and sulfonyl-ornithine analogs (21, 23, 25) were synthesized by acylation of free amino intermediates (19a,b) derived from tert-butoxycarbonyl-ornithine analogs (17a,b). A free ornithine analog (18) did not strongly inhibit Meth A cell growth, whereas all N(omega)-acyl-, sulfonyl-, carbamoyl- and aryl-ornithine analogs (9, 11, 21, 23, 25, 30, 36) exhibited much more potent inhibitory activities against both DHFR and Meth A cell growth. In particular, compounds 9c, 21k and 36a also showed remarkable growth-inhibitory activities against methotrexate-resistant CCRF-CEM cells. These results demonstrate that the potent inhibitory activities of N(omega)-masked ornithine analogs against the growth of Meth A cells and methotrexate-resistant CCRF-CEM cells, results from effective uptake via reduced folate carrier and their potent DHFR inhibition. 相似文献
28.
Fuyuki Ito Nobuaki Tanaka Akio Katsuki Akikazu Kakehi Tsuneo Fujii 《Research on Chemical Intermediates》2004,30(3):331-336
Three types of flavylium salts (FVs, yellow, green and red) have been synthesized and the colors depended on recrystallization conditions. The existence of these color states was confirmed by diffuse reflectance spectra. The spectra were almost the same as the absorption spectra in ethanol solution. The molecular state of FVs in crystals will be the same as that in solutions. The crystal colors of the FVs are controlled by the recrystallization conditions. 相似文献
29.
Application of dibutyltin oxide method to regioselective acylation and alkylation of tylosin at C-4' 总被引:1,自引:0,他引:1
K Kiyoshima M Sakamoto T Ishikura Y Fukagawa T Yoshioka H Naganawa T Sawa T Takeuchi 《Chemical & pharmaceutical bulletin》1989,37(4):861-865
4'-O-Acyl-, 4'-O-alkyl- and 4'-deoxy-tylosin derivatives were synthesized using 2'-O-acetyl-3',4'-O-(dibutyl-stannio)tylosin as a synthetic intermediate. The in vitro biological evaluation showed that the new derivatives were active against macrolide-resistant clinical isolates of bacteria and mycoplasmas, and that they were resistant to hepatic esterase. 相似文献
30.
T. Kambara K. Hasegawa H. Yoshioka Y. Kamiya T. Kotani K. Tabei 《Journal of Radioanalytical and Nuclear Chemistry》1977,36(1):87-94
Variations of125Sb valency states in HCl solutions were investigated by the use of the N-benzoyl-N-phenyl-hydroxylamine (BPHA) extraction
method.125Sb(V) is completely reduced to Sb(III) by one hour refluxing in conc. HCl.125Sb(III) is gradually oxidized to Sb(V) in solutions of low HCl concentrations by the effects of their own radiations. Natural
light promotes such oxidation reactions. By utilizing such oxidation-reduction effects125Sb(V) can be easily prepared from125Sb(III) and also125Sb(III) can be prepared by the reduction of Cl
aq
−
. Their valency states were stable on keeping them in brown-colored bottles at 6M HCl concentrations. 相似文献