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61.
62.
The synthesis of cyclic, branched, and bicyclic oligonucleotides was performed by copper-catalyzed azide-alkyne cycloaddition assisted by microwaves in solution and on solid support. For that purpose, new phosphoramidite building blocks and new solid supports were designed to introduce alkyne and bromo functions into the same oligonucleotide by solid-phase synthesis on a DNA synthesizer. The bromine atom was then substituted by sodium azide to yield azide oligonucleotides. Cyclizations were found to be more efficient in solution than on solid support. This method allowed the efficient preparation of cyclic (6- to 20-mers), branched (with one or two dangling sequences), and bicyclic (2 x 10-mers) oligonucleotides. 相似文献
63.
Luvino D Baraguey C Smietana M Vasseur JJ 《Chemical communications (Cambridge, England)》2008,(20):2352-2354
The synthesis of a borononucleotide analogue of thymidine and its association towards the formation of new borono-linked dimers is described. 相似文献
64.
65.
Heat and Mass Transfer - The buoyancy-induced flows of non-Newtonian fluids in a horizontal fluid saturated porous layer is studied analytically and numerically using the power-law model to... 相似文献
66.
DNA‐Templated [2+2] Photocycloaddition: A Straightforward Entry into the Aplysinopsin Family of Natural Products 下载免费PDF全文
Nicolas Duchemin Adam Skiredj Justine Mansot Karine Leblanc Dr. Jean‐Jacques Vasseur Dr. Mehdi A. Beniddir Dr. Laurent Evanno Prof. Dr. Erwan Poupon Prof. Dr. Michael Smietana Dr. Stellios Arseniyadis 《Angewandte Chemie (International ed. in English)》2018,57(36):11786-11791
Biosynthetic considerations inspired us to harness the templating properties offered by DNA to promote a [2+2] photoinduced cycloaddition. The method was developed based on the dimerization of (E)‐aplysinopsin, which was previously shown to be unproductive in solution. In sharp contrast, exposure of this tryptophan‐derived olefin to light in the presence of salmon testes DNA (st‐DNA) reproducibly afforded the corresponding homo‐dimerized spiro‐fused cyclobutane in excellent yields. DNA provides unique templating interactions enabling a singular mimic of the solid‐state aggregation necessary for the [2+2] photocycloaddition to occur. This method was ultimately used to promote the prerequisite dimerizations leading to both dictazole B and tubastrindole B, thus constituting the first example of a DNA‐mediated transformation to be applied to the total synthesis of a natural product. 相似文献
67.
B Gerland A Goudot G Pourceau A Meyer S Vidal E Souteyrand JJ Vasseur Y Chevolot F Morvan 《The Journal of organic chemistry》2012,77(17):7620-7626
Homo- and heterofunctionalized glycoclusters with galactose and/or fucose residues targeting both PA-IL and PA-IIL lectins of Pseudomonas aeruginosa were synthesized using "Click" chemistry and DNA chemistry. Their binding to lectins (separately or in a mixture) was studied using a DNA Directed Immobilization carbohydrate microarray. Homoglycoclusters bind selectively to their lectin while the heteroglycocluster binds simultaneously both lectins with a slight lower affinity. 相似文献
68.
Ohara K Jacquinet JC Jouanneau D Helbert W Smietana M Vasseur JJ 《Journal of the American Society for Mass Spectrometry》2009,20(1):131-137
A better understanding of the biological roles of carbohydrates requires the use of tools able to provide efficient and rapid structural information. Unfortunately, highly acidic oligomers-such as polysulfated oligosaccharides-are very challenging to characterize because of their high polarity, structural diversity, and sulfate lability. These features pose special problems for matrix-assisted laser desorption/ionization mass spectrometric (MALDI-MS) analysis because polysulfated carbohydrates exhibit poor ionization efficiency and usually do not produce any signal. The present report demonstrates how MALDI-MS can be used to derive structural and compositional information from pure and mixed fractions of polysulfated oligosaccharides. Indeed, pyrenemethylguanidine (pmg, a derivatizing agent and ionization efficiency enhancer) was used for the analysis of di- to decasaccharides, carrying from two to nine sulfate groups. The method is applied to various highly sulfated chondroitin and carrageenan oligosaccharides as well as to the analysis of mixtures of compounds. In the mass spectra, the observation of a unique pmg-complexed ladder of peaks in both ionization modes allows an easy and rapid determination of both the number of sulfate groups carried by the analyte and its molecular weight. Moreover, we have developed a software tool for the rapid and automatic structural elucidation of carrageenans based on the mass spectra obtained. 相似文献
69.
Bouillon C Meyer A Vidal S Jochum A Chevolot Y Cloarec JP Praly JP Vasseur JJ Morvan F 《The Journal of organic chemistry》2006,71(12):4700-4702
A versatile approach has been developed for the multiple labeling of oligonucleotides. First, three linkers as a H-phosphonate monoester derivative were condensed on a solid-supported T12 to introduce H-phosphonate diester linkages which were oxidized in the presence of propargylamine. Second, three galactosyl azide derivatives were conjugated to the solid-supported three-alkyne-modified T12 by a 1,3-cycloaddition so-called "click chemistry" in the presence of Cu(I) assisted by microwaves. 相似文献
70.
A numerical study has been carried out on mixed convection and conduction in open cavities. The study covers the Rayleigh number from 10 to 106, the Reynolds number from 1 to 103 andk r =k w /k a from 1 to 100 forPr=0.72 (air) and cavity aspect ratioB from 0.8 to 1.3. The flow is assumed to be laminar and two-dimensional. The density variation is taken into account by the Boussinesq approximation. The controlvolume approach is used for solving the governing equations of conjugate heat transfer involving conduction in the walls. Streamlines and isotherms in the system are produced and the results are represented in terms of the Nusselt number as function of other parameters. Correlations are derived to calculate heat transfer through the cavity openings. 相似文献