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71.
This paper describes an efficient synthetic route for various types of novel carbocyclic nucleosides. The required stereochemistry of the targeted nucleosides was successfully obtained with use of Grubbs cyclization and Trost allylic alkylation from the carbohydrate chiral template "D-lactose". 相似文献
72.
Martin R. Bryce Peter J. Skabara Adrian J. Moore Andrei S. Batsanov Judith A.K. Howard Vanessa J. Hoy 《Tetrahedron》1997,53(52):1002-17794
Reactions of tetrathiafulvalenyllithium (TTF-Li) with a range of aldehydes and ketones have been explored for the first time, to provide an efficient route to mono-functionalised TTF derivatives of general formulae TTF-CH(OH)R (R = alkyl, phenyl, tetrathiafulvalenyl and ferrocenyl) and TTF-CR(OH)R′ (R = alkyl, phenyl, R′ = alkyl, phenyl, tetrathiafulvalenyl, ferrocenyl, and R-R′ = fluorenyl). Subsequent transformations involving the reactive alcohol group of some of these compounds are reported. The structures of the three title compounds have been established by single-crystal X-ray analysis. 相似文献
73.
Howard C. Clark Anil B. Goel Chun S. Wong 《Journal of organometallic chemistry》1980,190(4):C101-C104
Simple synthetic routes to the mixed ligand complexes PtLL'X2 and PtLL'XY (L' = PEt3; L = phosphine, arsine, etc.; X = Cl and Y = Cl, H or Me) are described; unexpectedly, these display an extensive chemistry without disproportionation, although in some cases ligand scrambling does occur. 相似文献
74.
Conformations of 2-methoxytetrahydropyran as a model for the six-membered ring in aldopyranosides have been calculated by the PCILO method using the algorithm of the conjugated gradient to optimize the geometry. The calculated geometry of the fourteen basic forms of 2-methoxytetrahydropyran was found to be in agreement with the available data obtained by X-ray diffraction of pyranosides. The results indicate differences in the geometry of 2-methoxytetrahydropyran resulting from the change of the axial vs. equatorial position of the methoxyl group. These changes are particularly meaningful in the values of bond angles and they are in agreement with the anomeric and exoanomeric effects. The experimentally found differences in the energies of an axial (4
C
1) and equatorial (1
C
4) conformer, G = 2.9–3.7 kJ/mol, and the dipole moment, = 1.20 ± 0.05 D (1D = 3.33 10–30mAs) agree well with the calculated values E = 3.18 kJ/mol and <> = 1.18 D which, in turn, suggest that the axial conformer is preferred over the equatorial one by a ratio a:e = 78:22. 相似文献
75.
S. N. Dmitrieva N. I. Sidorenko A. I. Vedernikov L. G. Kuz’mina J. A. K. Howard T. M. Buslaeva S. P. Gromov 《Russian Chemical Bulletin》2007,56(5):993-1002
The condensation reaction of 1,2-bis(2-haloethoxy)-4-nitrobenzenes with acyclic α,ω-(oxa)alkanedithiols in the presence of
alkali metal carbonates produced a series of nitrobenzodithiacrown ethers with macrocycles of different size. The structures
of three ethers were established by X-ray diffraction. A new method was developed for the synthesis of nitrobenzomonothia-15-crown-5
ether. Nitro derivatives of benzodithiacrown ethers were tested as reagents for extraction of palladium(II), platinum(IV), and rhodium(III) from hydrochloric acid solutions. Extraction of PdII salts was found to be highly selective compared to that of PtIV and RhIII salts. Benzodithia-15-crown-5 ether is the most efficient extractant for palladium(II). Reduction of nitrobenzothiacrown ethers with hydrazine hydrate in the presence of a platinum catalyst afforded their amino
derivatives.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 958–966, May, 2007. 相似文献
76.
Laser-induced luminescence in quasi-one-dimensional Ba(Pt, Ni)(CN)4·nH2O crystals has been measured from 5 to 300 K. A well-defined luminescence peak is observed, corresponding to an excited electronic state of platinum and nickel. Energy transfer from this Pt—Ni excited state to Pt(CN)42? clusters is found to be very much dependent on the temperature. 相似文献
77.
Bruce M. Howard William Fenical Edward V. Arnold Jon Clardy 《Tetrahedron letters》1979,20(31):2841-2844
The structure of a unique bromine-containing ketal, obtusin (), has been determined by spectral and X-ray crystallographic techniques. Obtusin is a natural component of the Mediteranean red alga . 相似文献
78.
Howard C. Haas Monis J. Manning Martin H. Mach 《Journal of polymer science. Part A, Polymer chemistry》1970,8(7):1725-1730
Differential thermal analysis has been used to study the fusion of aqueous thermally reversible gels of gelatin and polyacrylylglycinamide (PAG). In the case of gelatin gels, endotherms close to the melting point are readily observed and these are sometimes preceeded by a small exothermic heat of gel reorganization. Calculations are presented to show that breaking of the gelatin gel network requires only a small fraction of the observed endothermic heat of fusion and that most of the heat is required for melting larger crystallites within gelatin aggregates and for perhaps a helix → coil transition. Failure to observe endotherms by DTA over the known temperature range of fusion of PAG gels is consistent with prior measurements and conclusions. The noncrystallinity of PAG gels and soluble aggregates together with a heat of crosslinking of only ?5 to ?10 kcal/mole of crosslinks places the heat of fusion of PAG gels outside the lower limits of DTA sensitivity. 相似文献
79.
Seo YJ Jeon MH Lee JH Lee YJ Youn HJ Ko JH Lee JH 《Experimental & molecular medicine》2005,37(6):624-630
Bis (Bag-3, CAIR), a Bcl-2-interacting protein, promotes the anti-apoptotic activity of Bcl-2 and increased levels of Bis have been observed in several disease models. The involvement of Bcl-2 and some Bcl-2-binding proteins in differentiation has recently been reported. However, the relevance of Bis to cellular differentiation remains unknown. The findings herein show that Bis expression is up-regulated during the differentiation of HL-60 cells. To investigate the effect of Bis expression on differentiation, we established Bis-overexpressing HL-60 cells (HL-60-bis). HL-60-bis cells have a low nuclear: cytoplasmic ratio and indented nucleus in Wright- Giemsa staining, and an increased expression of CD11b in immunofluorescence study, indicating the promotion of differentiation. The overexpression of Bis also resulted in a retarded cell growth rate, accompanied by the accumulation of HL-60 cells at the G0/G1 phase of the cell cycle, which was sustained during the differentiation process. Western blot analysis revealed that the expression of p27, a representative inducer of cell cycle arrest at the G1 phase, was increased 2.5-fold in HL-60-bis cells compared to HL-60-neo cells. These results suggest that the Bis induced growth inhibition of HL-60 cells promotes G0/G1 phase arrest via up-regulation of p27, which seems to be a prerequisite for differentiation. Further studies will be required to define the exact roles of Bis on cellular differentiation more precisely. 相似文献
80.
FrankH. Allen Raju Mondal NigelA. Pitchford JudithA.K. Howard 《Helvetica chimica acta》2003,86(4):1129-1139
Symmetry‐modified principal‐component analysis has been used to visualise the geometrical distortions of three‐coordinate metal centres observed in crystal structures retrieved from the Cambridge Structural Database. It is shown that compounds of Cu, Ag, Hg, Zn, and Au dominate the dataset, and exhibit distortions away from the trigonal planar archetype towards a) T‐shaped and b) Y‐shaped geometries. A small number of compounds, principally of Cu and Ag, also show distortions towards trigonal pyramidal geometries. The interconversions from Y‐shaped geometries, through the trigonal planar form to T‐shaped geometries are clearly mapped by the PC analysis. For HgII complexes, it is possible to interpret the transition from T‐shaped geometries to the trigonal planar form in terms of a reaction pathway for ligand addition to linear L1? HgII? L2 species. 相似文献