A number of novel phosphate triester derivatives of the anti-cancer nucleoside analogue araC have been prepared by a rapid 2-step procedure, not necessitating prior sugar protection. Spectroscopic and lipophilicity data have been collected on these compounds. An in vitro assay indicated inhibition of thymidine incorporation by mammalian epithelial cells, by each of these compounds, in the range 3-300 microM. Moreover, the degree of inhibition showed a close correlation to chemical structure; in particular, there was a clear relationship between inhibition of thymidine incorporation and log(P). These results are consistent with cellular penetration by the intact phosphate triesters and intracellular action by an unspecified mechanism. Triethyl phosphate is inactive under the conditions of the test.

International audienceOrganotin compounds particularly dibutyltin dilaurate, are commonly used as catalysts in coatings or adhesive materials to crosslink silyl modified polymers. However, environmental concerns should lead before 2020 to ban organotin compounds due to their high toxicity. Thus new catalysts must be developed. According to the different types of catalytic systems, i.e. acid, basic or metal containing catalysts, a large variety of candidates should be tested. Thus a high-throughput screening (HTS) method could be an interesting tool for the detection of new efficient catalysts to substitute organotin compounds. We report a global HTS method, compatible with organic amino or acid catalysts libraries, as well as with metal-containing librarie

Despite their instability, carbon-centered radicals have been involved as intermediates in many organic transformations that are essential to mankind. Radical polymerization,1-5 for example, provides a large part of polyacrylates and polystyrenes used as commodities in our everyday life. On a molecular level, the outcome of radical-mediated reactions is usually very different from those obtained via classical ionic based organic reactions. This is known since the 1930’s6 and has witnessed extensive developments such as radical cyclization or Atom Transfer Radical Additions (ATRA)7-9 . Radical processes10 typically begin with an initiation step in which the first radical species is created. It is eventually followed by one or several transfer steps which ultimately conduct to the formation of the main radical intermediate responsible for the reaction. The propagation steps of the radical chain are a succession of radical based transformations which, combined, outline the expected transformation.

Atom Transfer Radical Additions of alkyl halides to alkenes was developed using a low amount of a stable initiator, amine borane complexes. Thanks to a slow hydroboration step, the overall...

Cross-linking of silyl-modified polymers occurs at the alkoxysilane groups attached to the ends of polymer chains by hydrolysis and polycondensation mechanisms in the presence of moisture. During these reactions, three different physical states can be identified (viscous, skin effect and cross-linked state). Knowledge of the evolution of these states at each reaction time is essential to determine the open time for the adhesive industry and is generally obtained by a manual method. Automation of this monitoring could avoid operator error and could be used for very long cross linking reactions or to screen a large number of catalysts. Thus, a contactless micro process technology was developed to correlate these physical states with an optical technology, Raman spectroscopy, by monitoring the decrease in intensity of the Si-OCH 3 groups during chemical reactions. This online characterization method can also be used to compare the efficiencies of several catalysts for the cross-linking of silylmodified polymers, using a minimum amount of chemical materials.