Sébastien Noël

Caprolactam from renewable resources: catalytic conversion of 5-hydroxymethylfurfural into caprolactone

In zijn dissertatie beschrijft dhr. Teddy experimentele onderzoek naar de omzetting van 5-hydroxymethylfurfural (HMF) naar caprolactam, de uitgangsstof voor nylon 6. Het HMF kan op zijn beurt weer gemaakt worden uit lignocellulosische biomassa, zoals hout of grasachtig afval, is dan dus een groen basismateriaal. C6-suikers in lignocellulosische biomassa zijn interessante startmaterialen voor groene chemicalien met grote toepassingsmogelijkheden. HMF kan gemaakt worden uit D-fructose en mogelijk ook uit goedkopere suikers als D-glucose. Een grote uitdaging voor dit onderzoek betrof de ontwikkeling van katalytische routes voor de omzetting van HMF naar 1,6-hexanediol (1,6-HD). Vier verschillende routes zijn onderzocht: de directe hydrogenatie van HMF naar 1,6-HD, een tweestapsroute via 2,5-THF-dimethanol (THFDM), een driestapssynthese via THFDM en 1,2,6-hexanetriol (1,2,6-HT) en ten slotte een vierstapssynthese via THFDM, 1,2,6-HT en tetrahydro-2H-pyran-2-ylmethanol (2-THPM).

A phylogenetic analysis of the Trypanosoma cruzi genome project CL Brener reference strain by multilocus enzyme electrophoresis and multiprimer random amplified polymorphic DNA fingerprinting.

We have assessed the phylogenetic status of the Trypanosoma cruzi Genome Project CL Brener reference strain by multilocus enzyme electrophoresis (MLEE) and multiprimer random amplified polymorphic DNA (RAPD) including a set of cloned stocks representative of the whole genetic diversity of T. cruzi. MLEE and RAPD data gave congruent phylogenetic results. The CL Brener reference strain fell into the second major phylogenetic subdivision of T. cruzi, and was genetically very close to the Tulahuen reference strain. No reliable RAPD character and only one MLEE character permitted us to distinguish between the CL Brener and Tulahuen reference strains. In contrast, many RAPD and MLEE characters were able to distinguish between the CL Brener reference strain and the other T. cruzi genotypes analyzed here, in particular the formerly described principal zymodemes I, II and III. It is suspected that both CL Brener and Tulahuen are hybrid genotypes, a fact that should be taken into account when interpreting sequence data. Moreover, our study confirms that the species T. cruzi is genetically very heterogeneous. We recommend future comparison of sequencing data from the CL Brener reference strain with those of at least one radically distinct T. cruzi genotype, belonging to the other major phylogenetic subdivision of this species.

Compared vectorial transmissibility of pure and mixed clonal genotypes of Trypanosoma cruzi in Triatoma infestans

Abstract A total of 15 mixtures involving 9 different stocks attributed to the 19/20, 32 and 39 major clonal genotypes of Trypanosoma cruzi were used to infect third-instar nymphs of Triatoma infestans via an artificial feeding device. Three biological parameters were considered: (1) the percentage of infected insects (%II), (2) the number of flagellates per insect (NFI), and (3) the percentage of trypomastigotes per insect (%DIF). Genetic characterization by both multilocus enzyme electrophoresis (MLEE) and random amplification of polymorphic DNA (RAPD) indicated that in almost all cases (87%), mixtures remained present after completion of the whole cycle in the insect vector. Two lines of comparison were performed: (1) pure clonal genotypes versus corresponding mixed clonal genotypes and (2) the␣actual behavior of mixed clonal genotypes versus the expected behavior of the theoretical mixture (i.e. the␣arithmetic mean of the results observed for each of the two clonal genotypes taken separately). Statistical analyses of the variables were made difficult because of the presence of large standard deviations. Nevertheless, in several cases, mixtures differed significantly from pure clonal genotypes, and in one case the actual mixture differed significantly from the theoretical mixture. In some cases, interaction (either potentialization or reciprocal inhibition) could be suspected.

Is Leishmania (Viannia) peruviana a distinct species? A MLEE/RAPD evolutionary genetics answer

Abstract A set of 38 Leishmania stocks from the Andean valleys of Peru was characterized by both Multilocus Enzyme Electrophoresis (MLEE) and Random Amplified Polymorphic DNA (RAPD). Data were analyzed in terms of taxonomy and evolutionary genetics. Synapomorphic MLEE and RAPD characters, clear-cut clustering, and strong agreement between the phylogenies inferred from either MLEE or RAPD supported the view that Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis correspond to two closely related, but distinct monophyletic lines (clades) and can therefore be considered as “discrete typing units” (DTUs). The question whether the L. (V.) peruviana DTU deserves species status is dependent upon the desirability of it, in terms of epidemiological and medical relevance. A previous Orthogonal Field Alternating Gel Electrophoresis (OFAGE) analysis of the same L. (V.) peruviana isolates was published by Dujardin et al. (1995b). The data from the different markers (i.e. MLEE, RAPD and OFAGE) were compared by population genetics analysis. RAPD and OFAGE provided divergent results, since RAPD showed a strong linkage disequilibrium whereas OFAGE revealed no apparent departure from panmictic expectation. MLEE showed no linkage disequilibrium. Nevertheless, contrary to OFAGE, this is most probably explainable by the limited variability revealed by this marker in L. (V.) peruviana (statistical type II error). RAPD data were consistent with the hypothesis that the present L. (V.) peruviana sample displays a basically clonal population structure with limited or no genetic exchange. Disagreement between RAPD and OFAGE can be explained either by accumulation of chromosomal rearrangements due to amplification/deletion of repeated sequences, or by pseudo-recombinational events.

Cyclodextrins as growth controlling agents for enhancing the catalytic activity of PVP-stabilized Ru(0) nanoparticles

Cyclodextrins act as growth controllers in the synthesis of PVP-stabilized Ru(0) nanoparticles, leading to enhancement of the catalytic activity in the hydrogenation of furfural.

Ruthenium-containing β-cyclodextrin polymer globules for the catalytic hydrogenation of biomass-derived furanic compounds

The confinement of catalytically active metallic nanoparticles within discrete and robust microenvironments was successfully achieved by using a water-compatible three-dimensional β-cyclodextrin-based polymer. The strategy was examined using ruthenium through an aqueous colloidal approach involving the chemical reduction of ruthenium nitrosyl nitrate by sodium borohydride in the presence of a water-soluble β-CD polymer crosslinked with citric acid (poly(CTR-β-CD)). The advantage of this polymer for nanoparticle synthesis is that (i) additional stabilizing effects are exerted through steric interactions (crosslinked chains and β-cyclodextrin entities) and electrostatic interactions (ionisable–COOH groups) and (ii) accessible nanopockets are provided between the stable junctions of the polymer skeleton. The poly(CTR-β-CD) Ru(0) system was characterized at different stages of the synthesis by combining proton nuclear magnetic resonance spectroscopy, dynamic light scattering and transmission electron microscopy measurements. The results highlighted that, in contrast with a series of control colloidal ruthenium catalysts, the specific use of poly(CTR-β-CD) allowed not only the stabilization of smaller size-controlled ruthenium nanoparticles (approximately 1.8 nm) but also their confinement in individual superstructures having sizes mostly in the range of 50 to 100 nm. These polymer-encapsulated ruthenium nanoparticles were applied as catalysts for the aqueous phase hydrogenation of biomass-derived 2-furaldehyde and 3-(2-furyl)acrolein under mild reaction conditions, i.e. 303 K and 1 MPa. The high reactivity was related to the presence of individual globular objects acting as catalytic “microreactors”, in which the consecutive hydrogenation reactions and product/substrate diffusional exchanges can occur efficiently in the confined spaces. The robustness of the system was demonstrated through recycling experiments and TEM characterizations after catalytic tests.

Carboxylated polymers functionalized by cyclodextrins for the stabilization of highly efficient rhodium(0) nanoparticles in aqueous phase catalytic hydrogenation

Rhodium(0) nanoparticles stabilized by a polymer containing carboxylate and β-cyclodextrin moieties have high stability and catalytic activity for aqueous hydrogenation reactions of olefins and aromatic substrates. This catalytic system can be recycled and reused without loss of activity. These high catalytic performances can be attributed to conjugated electrostatic interactions (carboxylate groups) and steric interactions (polymer structure and β-cyclodextrin moiety).

Direct synthesis of tricyclic 5H-pyrido[3,2,1-ij]quinolin-3-one by domino palladium catalyzed reaction

Unexpectedly, the palladium catalyzed coupling reaction of acrolein with 8-bromoquinoline gave 5H-pyrido[3,2,1-ij]quinolin-3-one in a single step.

Mesoporous RuO2/TiO2 composites prepared by cyclodextrin-assisted colloidal self-assembly: towards efficient catalysts for the hydrogenation of methyl oleate

Mesoporous RuO2/TiO2 composites were prepared using a template-directed colloidal self-assembly approach combined with a cyclodextrin (CD)-assisted aqueous impregnation method. The supramolecular assemblies formed between the randomly methylated β-cyclodextrin (RaMeβ-CD) and the block copolymer P123 acted as a template for the formation of a highly porous TiO2 network over which uniform dispersion of ruthenium nanoparticles was achieved. By combining dynamic light scattering, X-ray diffraction, N2-adsorption, temperature-programmed reduction, field-emission scanning electron microscopy and high-resolution transmission electron microscopy, we show that CD-based assemblies provide a versatile and easily accessible toolbox with different functionalities for generating metal-supported catalysts with controlled pore architecture and uniform metal distribution. The performance of these supported catalysts was evaluated in the liquid phase hydrogenation of methyl oleate (MO, C18:1) to methyl stearate (MS, C18:0). Control of ruthenium dispersion into the large pores of RaMeβ-CD-P123-templated TiO2 material enhanced catalyst activity and selectivity for the hydrogenation of the internal CC bond and permitted catalyst separation and reuse without loss of activity. Our findings highlight the pivotal role played by the CD-based assemblies on the performance of supported ruthenium catalysts.

Acid-tolerant cyclodextrin-based ruthenium nanoparticles for the hydrogenation of unsaturated compounds in water

A water-soluble β-cyclodextrin polymer synthesized by crosslinking β-cyclodextrin with epichlorohydrin and glycidyltrimethylammonium chloride allowed the stabilization of ruthenium nanoparticles not only in basic aqueous medium but also in acidic medium. The aqueous ruthenium colloidal suspensions obtained with this polymer were active as catalysts for the hydrogenation of a large variety of unsaturated compounds including aromatic or fatty acids. The recycling of this catalytic system was attested through ten consecutive runs without loss of stability and activity, demonstrating its robustness.