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61.
Māris Turks Inta Strakova Kirils Gorovojs Sergey Belyakov Yuri A. Piven Tatyana S. Khlebnicova Fedor A. Lakhvich 《Tetrahedron》2012,68(31):6131-6140
A new route toward 4-acylamino- and 4-amino-substituted tetrahydroindazoles is disclosed. The title compounds are obtained in good to excellent yields in the Ritter reaction between 4-hydroxy-tetrahydroindazoles and various nitriles. The reactivity of the tetrahydroindazole-derived carbenium ion is both sufficiently high to react with trichloroacetonitrile and sufficiently selective to resist the azide functionality within its structure. The present approach adds a method to the toolbox of tetrahydroindazole chemistry and facilitates the structural modifications of the scaffold, which has found important applications in medicinal chemistry. 相似文献
62.
63.
Gabel-Jensen C Gammelgaard B Bendahl L Stürup S Jøns O 《Analytical and bioanalytical chemistry》2006,384(3):697-702
To elucidate how selenite is metabolised in the intestine after oral intake, it was incubated with homogenized epithelial
cells from pigs. When the metabolites were analysed by LC–ICP–MS, two major selenium metabolites were separated in the supernatant
from the homogenate. These metabolites were formed instantly but disappeared within 15 min. No other selenium-containing compounds
appeared during this time. Hence, the secondary reaction products were either volatilised or precipitated. To verify the identity
of the compounds, a larger amount of selenite was incubated with epithelial cells. The presence of Cys-Se-SG and GS-Se-SG
was verified by LC–ESI-MS. Selenotrisulfides were synthesized by reaction of L-cysteine and L-glutathione with sodium selenite. The reaction mixture contained three main products: selenodicysteine (Cys-Se-Cys), selenocysteine
glutathione (Cys-Se-SG), and selenodiglutathione (GS-Se-SG). The two transient selenium compounds in the epithelial cell incubation
mixture co-eluted with the synthesized Cys-Se-SG and GS-Se-SG, respectively. The identities of these compounds were verified
by LC–ESI-MS. Hence, these selenium metabolites have now been identified by ESI-MS after isolation from epithelial cells. 相似文献
64.
Hadronization in simple models of quark systems is discussed with emphasis on the combinatorial aspects. The numberN of quarks and the numberN c of colours are the relevant variables. In onedimension and in the meson and baryon sector the problem is completely soluble. When multiquark hadrons are included an iterative procedure still allows a complete solution. Higher dimensions are difficult to treat but global hadronization, without dimensionality constraints, is again soluble. As a general result the baryon/meson ratio is, for large quark densities, rather large, ?1/3 and may grow without limit asN→∞. 相似文献
65.
Jekaterina Rjabova Vitālijs Rjabovs Antonio J. Moreno Vargas Elena Moreno Clavijo Māris Turks 《Central European Journal of Chemistry》2012,10(2):386-394
Recently, monosaccharide-triazole conjugates have proved to possess a large variety of useful biological activities. This
paper describes synthesis of a new series of 3-deoxy-3-C-triazolylmethyl-allose derivatives. These new compounds are obtained from acetonide-protected 3-deoxy-3-azidomethyl allose
and commercial alkynes via Cu(I) catalyzed 1,3-dipolar cycloaddition. The obtained molecular scaffolds differ from those described
earlier by the presence of a methylene linker (-CH2-) between the C(3) of allose and the triazole moiety. It was demonstrated that acetonide-protected monosaccharide, 3-deoxy-3-C-(4-phenyl-1H-1,2,3-triazol-1-yl)methyl-1,2:5,6-di-O-isopropylidene-α-d-allofuranose, inhibited α-L-fucosidase for 26% at 0.1 mM concentration, but a deprotected analog, 3-deoxy-3-C-(4-(4-tert-butylphenyl)-1H-1,2,3-triazol-1-yl)methyl-β-d-allofuranose, showed 15% inhibition of β-glucosidase at 1 mM concentration.
相似文献
66.
J.V. Kunzler T.A. Grandi W.H. Schreiner P. Pureur D.E. Brandāo 《Journal of Physics and Chemistry of Solids》1980,41(10):1023-1026
Electrical resistivity measurements have been performed on the Cu2Mn(Al1?xSnx) Heusler alloys, where x = 0; 0.05; 0.10; 0.15, in the temperature range of 4–800 K. The experimental curves clearly show the importance of the ferromagnetic character on the resistivities of the alloys. The results obtained are in agreement with an interpretation in terms of a spin-disorder model. 相似文献
67.
In the presence of sulfur dioxide and an acid promoter, (-)-(1E,3Z)-2-methyl-1-((1S)-1-phenylethoxy)penta-1,3-dien-3-yl isobutyrate reacts with (Z)-3-(trimethylsilyloxy)pent-2-ene giving a silyl sulfinate intermediate that undergoes, in the presence of palladium catalyst, a desilylation and retro-ene elimination of SO(2) with formation of (-)-(1Z,2S,3R,4S)-1-ethylidene-2,4-dimethyl-5-oxo-3-((1S)-1-phenylethoxy)-heptyl isobutyrate as major product. This ethyl ketone undergoes cross-aldol reaction with (2S)-2-methyl-3-[(tert-butyldimethylsilyl)oxy]propanal giving an aldol that is reduced into a stereoheptad corresponding to the C(19)-C(27)-segment of Rifamycins with high diastereoselectivity and enantiomeric excess. 相似文献
68.
P. Pazos-Capeáns M.C. Barciela-Alonso P. Herbello-Hermelo P. Bermejo-Barrera 《Microchemical Journal》2010,96(2):362-370
Chromium is an estuarine contaminant due to its industrial applications like leather tanning, dyeing or chromium plating. The most common explanation about the presence of this metal is the frequent estuarine spill, particularly in ecosystems like rivers, estuaries and coasts near anthropogenic activities.The purpose of this study is the investigation of the distribution and evolution of chromium in sediments of the surface layer of an estuary, determining directly the total content by electrothermal atomic absorption spectroscopy (ETAAS) using slurries. Results were correlated with the environmental conditions and the chemistry of the metal to have a partial overview of the potential risk of chromium presence in the water column and the biota of the estuary. The pH values, oxidation–reduction potential (ORP), elemental analysis (carbon, nitrogen and hydrogen content), and changes of total chromium with time were analysed. This information was used to establish the environmental conditions where chromium appeared, was transported and was accumulated in the marine sediments collected following a time evolution of two years. 相似文献
69.
[reaction: see text] In the presence of a Lewis or protic acid and at low temperature, 1,3-dioxy-1,3-dienes add to sulfur dioxide generating zwitterionic intermediates that can react with carbon nucleophiles such as allylsilanes. After a retro-ene elimination of SO(2), valuable polyketide precursors are obtained. 相似文献
70.
The analytical properties of N-nitroso-N-cyclohexylhydroxylamine (“hexahydrocupferron”) are described. This reagent is much more stable in acidic media than its analogue cupferron, but offers very similar reactions and sensitivities. The solubility, RF and pK values, u.v. and i.r. spectra for the reagent are given. Very sensitive qualitative tests for iron, vanadium and titanium are reported. A turbidimetric determination of aluminium(III), suitable for 0.6–10 μg Al ml-1, is evaluated. 相似文献