Catalytic And Economic Method Using As Catalyst the I-Si(CH3)3 Generated During The Condensation Of Silylated Base With Natural Phosphate Doped With KI (NP/KI)

Several D-ribonucleosides are prepared from 1-O-acetyl-2,3,5-tri-O-benzoyl-?-D-ribofuranoside  and trimethylsilylated nucleobases under mild conditions by using as catalyst I-Si(CH3)3 generated during the condensation of  silylated base with NP/KI. Keywords: I-Si(CH3)3 generated during the condensation of silylated base with NP/KI,one-step synthesis, and D-ribonucleosides

Novel approach to Synthesis of Pentofurano nucleoside assisted natural phosphate doped with CF3SO3H as catalyst

This article describes a method for the preparation of ribonucleosides using the solid-phase approach. Several D-ribonucleosides are prepared from 1-O-acetyl-2,3,5-tri-O-benzoyl-?-D-ribofuranoside and trimethylsilylated nucleobases under mild conditions by using natural phosphate doped with CF3SO3H (NP/ CF3SO3H) as catalyst. Keywords: Natural phosphate, CF3SO3H, D-Ribonucleoside

Heterogeneous Solid-Liquid Catalysis Of N-glycosylation By Natural Phosphate Doped With Potassium Iodide

Theone-step synthesis of several ?-D-ribonucleosides was performed in good yields under reflux in HMDS. Keywords: N-Glycosylation D-ribonucleosides,Natural phosphate doped with Potassium iodide KI (NP/KI), heterogeneous solid-liquid catalysi

Nucleoside analogues synthesis using natural phosphate doped with I2 (NP/I2) in HMDS

Several D-ribonucleosides are prepared from1-O-acetyl-2,3,5-tri-O-benzoyl-?-D-ribofuranoside and trimethylsilylated nucleobases under mild conditions by using natural phosphate doped with I2 as catalyst Keywords: Natural Phosphate doped with I2, one-step seynthesis. ?/?-D-ribonucleoside

A New Selective Synthesis Of D-Ribonucleosides In Acetonitrile With BSA Using NP/KI As Catalyst

The one-step synthesis of several ?-D-ribonucleosides was performed in good yields under reflux. Keywords: D-nucleosides, natural phosphate, catalyst, one-step seynthesis

Applications of Microwave in Organic Synthesis: A One-step Synthesis of Ribonucleosides using natural phosphate as solid catalyst

A clean, efficient and fast method for synthesis of ribonucleosides was developed, using  natural phosphate as solid catalyst catalysts supported in a solid phase  promoted by MW irradiation. Keywords: Natural phosphate, Ribonucleosides , Micowave irradiation

Synthesis of branched-phosphodiester and mannosecentered fucosylated glycoclusters and their binding studies with Burkholderia ambifaria lectin (BambL)

Universite Montpellier 2, Region Rhoˆne-Alpes Cluster Chimie. A.A.International audienceFive fucosylated glycoclusters exhibiting 4, 6 or 8 residues were synthesised with two different spatial environments based on mannose-centered and branched-phosphodiester scaffolds. Their synthesis was performed in solution using phosphoramidite chemistry to generate phosphodiester linkages, combined with Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The multivalent ligands were evaluated for their ability to bind to Burkholderia ambifaria Lectin (BambL). Binding evaluation was performed through inhibition of hemagglutination (HIA), surface plasmon resonance (SPR) and isothermal titration microcalorimetry (ITC). All fucosylated glycoclusters exhibited a higher affinity to BambL than methyl α-L-fucoside. A dissociation constant of 43 nM was observed for the fucocluster exhibiting four residues with the branched-phosphodiester spatial environment corresponding to a 22-fold increase in comparison with methyl α-L-fucoside. These multivalent fucoclusters represent the first example of ligands of high affinity to BambL

Molecular Basis for Nucleotide Conservation at the Ends of the Dengue Virus Genome

International audienceThe dengue virus (DV) is an important human pathogen from the Flavivirus genus, whose genome- and antigenome RNAs start with the strictly conserved sequence pppAG. The RNA-dependent RNA polymerase (RdRp), a product of the NS5 gene, initiates RNA synthesis de novo, i.e., without the use of a pre-existing primer. Very little is known about the mechanism of this de novo initiation and how conservation of the starting adenosine is achieved. The polymerase domain NS5PolDV of NS5, upon initiation on viral RNA templates, synthesizes mainly dinucleotide primers that are then elongated in a processive manner. We show here that NS5PolDV contains a specific priming site for adenosine 59-triphosphate as the first transcribed nucleotide. Remarkably, in the absence of any RNA template the enzyme is able to selectively synthesize the dinucleotide pppAG when Mn 2+ is present as catalytic ion. The T794 to A799 priming loop is essential for initiation and provides at least part of the ATP-specific priming site. The H798 loop residue is of central importance for the ATP-specific initiation step. In addition to ATP selection, NS5PolDV ensures the conservation of the 59-adenosine by strongly discriminating against viral templates containing an erroneous 39-end nucleotide in the presence of Mg 2+. In the presence of Mn2+, NS5Pol DV is remarkably able to generate and elongate the correct pppAG primer on these erroneous templates. This can be regarded as a genomic/antigenomic RNA end repair mechanism. These conservational mechanisms, mediated by the polymerase alone, may extend to other RNA virus families having RdRps initiating RNA synthesis de novo

Kilometer range filamentation

International audienceWe demonstrate for the first time the possibility to generate long plasma channels up to a distance of 1 km, using the terawatt femtosecond T&T laser facility. The plasma density was optimized by adjusting the chirp, the focusing and beam diameter. The interaction of filaments with transparent and opaque targets was studied