Personne :
Voyer, Normand

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Structures organisationnelles
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Université Laval. Département de chimie
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Voici les éléments 1 - 10 sur 14
  • Publication
    Accès libre
    Total synthesis of Crotogossamide using an on-resin concomitant cyclization/cleavage reaction
    (Phytochemical Society of Europe, 2018-05-22) Bérubé, Christopher; Borgia, Alexandre; Grenier, Daniel; Simon, Gaëlle; Voyer, Normand
    Crotogossamide, a cyclic peptide isolated from the latex of Croton gossypifolius, has been synthesized by a rapid and efficient Boc solid-phase peptide synthesis. The strategy takes advantage of the oxime resin nucleophile susceptibility and comprises the synthesis of a linear precursor followed by on-resin head-to-tail concomitant cyclization/cleavage. In addition, we report the first antimicrobial and antibiofilm investigations on Crotogossamide.
  • Publication
    Accès libre
    Crown-ether-modified cyclic dipeptides as supramolecular chiral catalysts
    (Gordon and Breach Science Publishers, 2017-10-20) Bérubé, Christopher; Voyer, Normand
    With the objective to develop supramolecular catalysts for useful chemical transformations, we report here a rapid and efficient solid-phase synthesis of novel cyclic dipeptides (crown-CDPs) with a diversity of L-DOPA derived crown ether substituents and stereochemistry. We prepared and characterized 14 crown-CDPs and evaluated their efficiency as supramolecular epoxidation catalysts in a water/hexanes biphasic system. Yields increase significantly in the presence of the crown-CDPs, though enantioselectivity depends on the nature of the substituents. The results reported constitute a useful approach for chiral epoxides of interest and further illustrate the potential of cyclic peptides as supramolecular catalysts.
  • Publication
    Accès libre
    Modulating the activity of membrane-active peptides through Zn(II) complexation
    (Pergamon Press, 2017-12-13) Paradis, Jean-Philippe; Tuck, Kellie L.; Voyer, Normand; Paquet-Côté, Pierre-Alexandre; Graham, Bimbil
    Seeking to increase the selectivity of antimicrobial peptides for prokaryotic cells, we incorporated a bis-dipicolyl amine (bis-DPA) ligand at the N-terminus of de novo designed model peptides. The Zn2·bisDPA complex increases the interaction of peptides with anionic model membranes, while decreasing interactions with zwitterionic model membranes. Further, it improves the peptides’ antimicrobial activity and decreases their hemolytic activity without substantial changes to their secondary structure. Therefore, incorporating a Zn2·bisDPA complex is a useful strategy to enhance the selectivity of antimicrobial peptides.
  • Publication
    Accès libre
    Chemical composition of the unexplored volatile fraction of betula glandulosa, a prevalent shrub in Nunavik, Québec
    (Wiley, 2021-12-09) Boudreau, Stéphane; Fernandez, Xavier; Voyer, Normand; Séguin, Jean-Christophe
    The volatile fraction of the leaves of Betula glandulosa Michx. has been investigated for its secondary metabolite composition by GC/MS and GC/FID. The rapid expansion of this shrub species in subarctic landscapes, like the ones found in Nunavik (Northern Québec, Canada), highly impacts ecosystem dynamics. Yet, despite its abundance, few phytochemical investigations have yet been conducted on this species. In this study, we present the first phytochemical investigation of the volatile metabolites of B. glandulosa leaves. Although no essential oil was isolated, volatile compounds were extracted from the hydrosol by steam distillation. The main metabolites observed were linalool (14.6–19.0 %), C6 oxylipins (known as green leaf volatiles, GLV; total of 18.2–40.2 %), eugenol (1.6–8.6 %) and α-terpineol (3.3–4.8 %). Dwarf birch is an important food source for insects and herbivores, so knowledge of its metabolite composition could help understand parts of its functional role in subarctic ecosystems. The composition of the volatile fraction could serve as marker for differentiating B. glandulosa from other dwarf birch species like Betula nana L.
  • Publication
    Accès libre
    Total synthesis and antimalarial activity of mortiamides A–D
    (Royal Society of Chemistry, 2019-05-20) Bérubé, Christopher; Gagnon, Dominic; Richard, Dave; Borgia, Alexandre; Voyer, Normand
    Mortiamides A–D (1–4) are head-to-tail cyclic heptapeptides that were identified from a novel Mortierella sp. isolate obtained from marine sediments from Northern Canada. Herein we report the first total synthesis of mortiamides A–D (1–4) on a solid support by concomitant cyclization/cleavage without any oligomerization side reactions, and overall yields up to 48%. We also report on the antiplasmodial activity of mortiamides A–D (1–4). We show that three out of the four tested mortiamides (A, B and D) have moderate antiplasmodial activity, while mortiamide D (4) exhibits low micromolar activity.
  • Publication
    Accès libre
    Total synthesis of pseudacyclins A-E by an on-resin head-to-side chain concomitant cyclization-cleavage reaction
    (Elsevier, 2018-10-16) Bérubé, Christopher; Borgia, Alexandre; Voyer, Normand
    Taking advantage of the nucleophile-sensitive ester link of oxime resin, a novel synthetic strategy was applied to the first synthesis of a type of cyclic peptides known as pseudacyclins A–E. The endocyclic ornithine side-chain part was incorporated by an on-resin acid-catalyzed concomitant cyclization-cleavage reaction after a selective deprotection of orthogonally protected ornithine. The synthetic methodology gives high macrocyclization yields and low oligomerization side-products. The combination used of solid-phase/solution-phase strategy was efficient to prepare pseudacyclins and could prove useful to prepare other natural cycle-tail peptides.
  • Publication
    Accès libre
    Total synthesis of chrysamide B
    (Elsevier, 2017-06-14) Bérubé, Christopher; Carpentier, Claudia; Voyer, Normand
    We report an efficient synthesis of the dimeric trans-epoxyamide chrysamide B, recently isolated from the deep-sea-derived fungus Penicillium chrysogenum SCSIO41001. Our synthetic strategy exploits a convergent approach using solid-phase peptide synthesis for the piperazine core and a Sharpless-Katsuki epoxidation to prepare the chiral epoxyacid. The double amidation final step provides chrysamide B that was thoroughly characterized with all spectra identical to those of the natural sample. The approach was devised to facilitate the preparation of a library of analogs of chrysamide B.
  • Publication
    Accès libre
    Crown ether helical peptides are preferentially inserted in lipid bilayers as a transmembrane ion channels
    (Wiley Periodicals, Inc., 2015-07-27) Bacon, Anne; Otis, François; Bürck, Jochen; Voyer, Normand; Savoie, Jean-Daniel
    Oriented circular dichroism was used to study the alignment crown ether-modified peptides. The influence of different N- and C-functionalities was assessed using at variable peptide:lipid ratios from 1:20 to 1:200. Neither the functionalities nor the concentration had any major effect on the orientation. The alignment of the 21-mer peptides was also examined with lipid membranes of different bilayer thickness. The use of synchrotron radiation as light source allowed the study of peptide:lipid molar ratios from 1:20 to 1:1000. For all conditions studied, the peptides were found to be predominantly incorporated as a transmembrane helix into the membrane, especially at low peptide concentration, but started to aggregate on the membrane surface at higher peptide:lipid ratios. The structural information on the preferred trans-bilayer alignment of the crown ether functional groups explains their ion conductivity and is useful for the further development of membrane-active nanochemotherapeutics.
  • Publication
    Accès libre
    Membrane assembly and ion transport ability of a fluorinated nanopore
    (Public Library of Science, 2016-11-11) Godbout, Raphaël; Auger, Michèle; Lagüe, Patrick; Auger, Maud; Otis, François; Légaré, Sébastien; Carpentier, Claudia; Voyer, Normand
    A novel 21-residue peptide incorporating six fluorinated amino acids was prepared. It was designed to fold into an amphiphilic alpha helical structure of nanoscale length with one hydrophobic face and one fluorinated face. The formation of a fluorous interface serves as the main vector for the formation of a superstructure in a bilayer membrane. Fluorescence assays showed this ion channel's ability to facilitate the translocation of alkali metal ions through a phospholipid membrane, with selectivity for sodium ions. Computational studies showed that a tetramer structure is the most probable and stable supramolecular assembly for the active ion channel structure. The results illustrate the possibility of exploiting multiple Fd-:M+ interactions for ion transport and using fluorous interfaces to create functional nanostructures.
  • Publication
    Accès libre
    Revisiting the Juliá–Colonna enantioselective epoxidation : supramolecular catalysis in water
    (Royal Society of Chemistry, 2017-04-12) Barbeau, Xavier; Bérubé, Christopher; Lagüe, Patrick; Voyer, Normand
    We describe an efficient epoxidation process leading to chiral epoxyketones using the reusable homo-oligopeptide poly-L-leucine (PLL) in pure water, without any organic co-solvent. A range of substituted epoxyketones can be accessed with good conversions and high enantioselectivities. Based on the experimental results and computational studies, we propose a mechanism that demonstrates the importance of both the α-helical structure and the presence of a hydrophobic groove of the homo-oligopeptide catalyst for reactivity and selectivity