1,721,056 research outputs found
SINTESI E PROPRIETA’ BIOLOGICHE DI LIGANDI GLICOSIDICI MULTIVALENTI
No full textProtein-carbohydrate interactions are at the heart of many important biological processes as the
adesion of bacteria and viruses to the cell surfaces. It is widely accepted that nature compensates for
the low intrinsic affinity of carbohydrate for proteins through the cooperative binding between
multiple copies of ligands and receptors so that a strong adhesion results. This important concept,
termed cluster effect, has stimulated the search for the construction of highly glycosylated ligands
to inhibit polyvalent processes as well as probe for cell-surfaces-binding events. The aim of this
PhD research work was the synthesis of calix[4]arene-based glycoclusters via Cu(I)-catalyzed
azide-alkyne coupling reaction (CuAAC), as well as the investigation of their biological proprieties.
The first research conducted dealt with the synthesis of sialoside clusters as potential inhibitors of
viruses infectivity. Tetra- and octavalent sialoside clusters were prepared exploiting the multiple
copper-catalyzed cycloaddition of a propargyl thiosialoside with calix[4]arene polyazides. It was
demonstrated that these unnatural motifs did not hamper the desired biological activity of the
sialoclusters. In fact, they were able to inhibit, at submillimolar concentrations, the
hemagglutination and the viral infectivity mediated both by BK and influenza A viruses.
Then, this thesis focused on the possibility to support C-glycoside clusters on microarrays to study
their affinity against lectins. To this aim C-glycosylated calix[4]arenes have been synthesized in
which four galactose residues are linked through a triazole tether to the upper rim of the macrocycle
cavity while an azido group is present on the opposite side. Next the calixsugars were grafted
through CuAAC on mono or dipropargyloxymethyl-propanediol moieties allowing the synthesis of
oligonucleotides bearing one or two calixarene glycoclusters, respectively. Finally, their affinity for
lectins PA-IL and RCA 120, galactose specific lectins from Pseudomonas aeruginosa and Ricinus
communis, respectively, were compared to that displayed by linear and antenna-type glycoclusters.
During the last period of the PhD work it was performed the immobilization of calix[4]arenebased
glycoclusters on TiO2 nanoparticles via Cu(I)-catalyzed azide-alkyne coupling reaction. The
strategy that has been followed involved first the grafting of bis-functionalized calix[4]arenes
(azido groups at upper rim and fenolic or carboxylic groups at the lower rim) onto TiO2 and then
multiple click copper(I)-catalyzed cycloaddition
to propargil glycosides. The glyconanoparticles
obtained were characterized by thermogravimetric analysis (TGA) and infrared spectroscopy. This
constitutes the first example of TiO2 nanoparticles coated by a monolayer of calix[4]arene-based
glycoclusters
Application of MCRs to the stereoselective synthesis of diverse heterocycles starting from chemoenzymatycally obtained chiral aldehydes
No full textBiocatalysis and MCRs: a Potential Green Strategy for the Synthesis of High-Added Value Compounds Starting from Biomass
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Diversity-oriented Synthesis of Benzoxazepinones through Coupling the Ugi Multicomponent Reaction with a Mitsunobu Cyclization
No full textAn unexpected benzylic oxidation in the multicomponent synthesis of simplified analogs of anchinopeptolides and eusynstyelamides
No full textThe combination of a photoinduced multicomponemt reaction with dimerization of the resulting intermediate can generate complex heterocyclic compounds in a stereodefined manner, with six new bonds and two quaternary carbons formed in just two steps. Remarkably, final heterocycles share the same core with two families of natural products, namely anchinopeptolides and eusynstyelamides. During the synthesis of simplified analogs of these compounds, we came across an unexpected oxidation and decided to study this process, trying to understand the factors able to influence it. We report here preliminary results showing that the structure of the substrates is a key factor in determining the oxidative or nonoxidative outcome of the dimerization reaction
Divergent and Stereocontrolled Synthesis of a Variety of Heterocycles Starting from Erythritol, Exploiting Biocatalysis and Multicomponent Reactions
No full textSynthesis of bio-based heterocycles from levulinic acid using the Ugi multicomponent reaction
No full textSynthesis and biological evaluation of β-Amyloid and Tau protein aggregation inhibitors for Alzheimer’s disease
No full textSynthesis of seven-membered nitrogen heterocycles through the Ugi multicomponent reaction
No full textThis paper reviews all the syntheses of 7-membered nitrogen heterocycles that are based on the Ugi multicomponent reaction. Different systems may be obtained in a diversity-oriented manner employing three general strategies: i) intramolecular Ugi reaction; ii) Ugi reaction followed by cyclization involving one additional functional group; iii) Ugi reaction followed by cyclization involving two additional functional groups
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