153 research outputs found
Conformational and docking studies of acyl homoserine lactones as a robust method to investigate bioactive conformations
International audienc
Sur le rĂŽle de la partie glucidique ou de la partie lipidique dans l auto-organisation des neoglycolipides (SynthĂšse de deux nouvelles familles de glycoamphiphiles et Ă©tude de leur comportement liquide cristallin)
Cette thĂšse est une contribution Ă l Ă©tude des relations structure propriĂ©tĂ©s dans le domaine de la glycoamphiphilie. Trois nouvelles familles de neoglycolipides ont Ă©tĂ© synthĂ©tisĂ©es, deux familles principalement destinĂ©es Ă apporter des Ă©lĂ©ments sur l Ă©tat liquide cristallin des glycolipides, et une troisiĂšme famille permettant d aborder l Ă©tude de nouvelles glycosondes fluorescentes. Plus de 50 produits finaux ont Ă©tĂ© prĂ©parĂ©s (et donc leurs trĂšs nombreux prĂ©curseurs) et caractĂ©risĂ©s structuralement par spectroscopie RMN, de masse, et par analyse Ă©lĂ©mentaire. Les propriĂ©tĂ©s liquides cristallines de ces nouveaux produits ont Ă©tĂ© ensuite Ă©tudiĂ©es par microscopie optique et DSC. L Ă©tude des propriĂ©tĂ©s liquides cristallines de la famille d Ă©thers montrent que la localisation de la chaine sur le squelette sucre modifie la rĂ©partition entre liaisons hydrogĂšne inter- ou intra molĂ©culaires entre tĂȘtes polaires sucres. L analyse du comportement thermotrope des glucostĂ©roĂŻdes, notamment ceux qui sont disubstituĂ©s, montre que les interactions lipide-lipide sont Ă©galement trĂšs importantes. Il a Ă©tĂ© observĂ© que ces systĂšmes complexes pouvaient adopter deux types d architectures au niveau supramolĂ©culaire en fonction de la flexibilitĂ© du systĂšme, laissant plus ou moins aux trois motifs prĂ©sents dans la molĂ©cule la libertĂ© de choisir leur prĂ©fĂ©rence d autoassociation. Les glycostĂ©roĂŻdes Ă©tant largement rencontrĂ©s dans la Nature, on peut considĂ©rer que ces observations nouvelles qui ont Ă©tĂ© apportĂ©es signalent que le comportement supramolĂ©culaire de telles molĂ©cules est potentiellement multiple. Enfin, une brĂšve exploration d une nouvelle famille de glycosondes fluorescentes a Ă©tĂ© abordĂ©e.In this study, we have synthesized two families of new carbohydrate-based amphiphilic derivatives: a series of alkyl glucoside ethers varying in terms of chain length and position on the sugar, and a series of glucosteroids varying in terms of alkyl spacer and, for the disutibstuted systems, in terms of alkyl side chain length. By the means of analytical methods, such as NMR spectroscopy, mass spectroscopy and elementary analysis, the structure of all the compounds was carefully established, as well as their purity. Their liquid crystalline behaviors were studied by the means of transmission light microscopy and differential scanning calorimetry. The two families of compounds which have been studied illustrate how much the behavior can be essentially related to polar interactions (H-bonding), therefore to the sugar moiety, for the ether series, or to hydrophobic interactions (lipid-lipid) in the glucosteroid series. In this latter series, preference for either steroid-stroid or steroid alkyl packing appears as an insight in understanding the behavior of complex lipids, showing potentially more than one conformational structure with important consequences on the supramolecular level, therefore to their potential biological role. This could be regarded as lipid denaturation by analogy to the protein denaturation. Also, when we see that compounds like the glycosteroids having an long chain ester -CAG, BbGL-I, are found to exist in Nature, and how much glycolipid-cholesterol interactions were recently shown to be critical in some biological processes, it is hoped that our observations can provide a new vision angle for the study of complex lipids and glycolipids. As a start to develop new probes targeting the lipid raft microdomain in membranes, we also explored a sequence towards carbohydrate laurdan hybrids. Further development of this strategy and evaluation of the biological properties is programmed within new collaborative projects.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF
Carboxymethyl TriâOâacetylâαâDâglucopyranoside 2âOâLactone â A Synthon for the Preparation of Neoglucoconjugates
International audienceCarboxymethyl triO -acetyl-α-D-glucopyranoside 2-O-lactone (CMGL), the bicyclic lactone obtained in two steps from isomaltulose by an oxidation-acetylation sequence, is a convenient synthon for connecting a glucosyl moiety with other constructs. Its synthesis and its reactivity with regards to various nucleophilic species are described and the different types of glucoconjugates which have been prepared by this method, as well as other sources of carboxymethyl glycosides, are reviewed
New functionalized scaffolds from hydroxymethylfurfural and glucosyloxymethylfurfural by MoritaâBaylisâHillman reaction with cycloalkenones
Synthesis of sugars embodying conjugated carbonyl systems and related triazole derivatives from carboxymethyl glycoside lactones. Evaluation of their antimicrobial activity and toxicity.
International audienceThe synthesis of a series of pyranoid derivatives comprising a conjugated carbonyl function and related triazole derivatives, structurally suitable for bioactivity evaluation, was achieved in few steps starting from readily available carboxymethyl glycoside lactones (CMGL). 3-Enopyranosid-2-uloses were generated by oxidation/elimination of tri-O-acylated 2-hydroxy pyranosides. Subsequent Wittig olefination provided stereoselectively 2-C-branched-chain conjugated dienepyranosides with (E)-configuration around the exocyclic double bond. A heterogeneous CuI/Amberlyst-catalyzed 'click' chemistry protocol was used to convert glycosides bearing a propargyl moiety into the corresponding 1,2,3-triazoles. These new molecules were screened for their in vitro antibacterial and antifungal activities and those containing conjugated carbonyl systems demonstrated the best efficacy. (N-Dodecylcarbamoyl)methyl enone glycerosides were the most active ones among the enones tested. The α-anomer displayed very strong activities against Bacillus cereus and Bacillus subtilis and strong activity toward Enterococcus faecalis and the fungal pathogen Penicillium aurantiogriseum. The corresponding ÎČ-anomer presented a very strong inhibitory effect against two fungal species (Aspergillus niger and P. aurantiogriseum). (N-Dodecyl-/N-propargyl/or N-benzylcarbamoyl)methyl dienepyranosides exhibited selectively a strong activity toward E. faecalis. Further acute toxicity evaluation indicated low toxic effect of the (N-dodecylcarbamoyl)methyl enone glyceroside α-anomer and of the carbamoylmethyl dienepyranosides N-protected with propargyl or benzyl groups
Sporopollenin exine capsules (SpECs) derived from Lycopodium clavatum provide practical antioxidant properties by retarding rancidification of an Ï-3 oil
In recent years the use of natural antioxidants in foodstuffs and personal care products has become increasingly important for consumers and therefore manufacturers. In this work, sporopollenin exine capsules (SpECs), extracted from spores of the common club moss Lycopodium clavatum L, have been shown to protect an Ï-3 oil from oxidation caused by natural light or accelerated oxidation with UV irradiation. The mechanism of action has been shown to be principally by free radical quenching as opposed to light shielding, supported by evidence of similarity in levels of protection when the ratio of SpECs to oil was 0.2 % w/v compared with 50 % w/w. The antioxidant effect is not materially altered by the extraction process from the raw material and is clearly an inherent property of the sporopollenin contained in the spores of L. clavatum due to the accessible phenolic groups on the surface on the SpECs. These results provide promising evidence that SpECs could be useful as a bio-sourced antioxidant for protecting Ï-3 oils and related oxidation-prone molecules
Catalytic etherification of sucrose with 1,2-epoxydodecane: investigation of homogeneous and heterogeneous catalysts
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