Glucosidases são enzimas que catalisam a hidrólise de ligações glicosídicas liberando unidades monossacarídicas de um terminal não redutor de um oligossacarídeo ou glicoconjugado. Iminoaçúcares são alcalóides piperidínicos polihidroxilados isolados de plantas (gênero Morus) e microrganismos (Bacillus), como nojirimicina (NJ) (1) e 1-desoxinojirimicina (DNJ) (2), os quais são descritos como inibidores de glucosidase. O potencial uso destes inibidores no tratamento de infecções virais, crescimento tumoral, metástases, diabetes, doença de Gaucher e osteoartrite tem motivado a comunidade científica na busca por novos derivados iminoaçúcares. Desse modo, a síntese de pseudodissacarídeos, contendo ambos resíduos de iminoaçúcar e glicopiranose, constitui uma estratégia interessante de obtenção desses derivados, apesar dos desafios envolvidos na geração da ligação entre estes dois açúcares. Por esta razão, foi utilizada a estratégia de click chemistry como uma ferramenta para introduzir uma ponte de grupo 1,2,3-triazol entre os açúcares a partir do acoplamento de azido-glicosídeo com N-propargil-iminoaçúcar. Desta forma, a síntese do iminoaçúcar N-propargílico (73), com função acetileno terminal, foi realizada em cinco etapas e foi usado na reação de cicloadição 1,3- dipolar com três derivados glicosídicos contendo grupo azido nas posições anomérica (C-1), C-3 ou C-6. A partir desta reação CuAAC (Copper(I)-catalyzed Azide-Alkyne Cycloaddition), três novos pseudo-dissacarídeos (77, 81 e 85) foram sintetizados em rendimentos moderados e foram, então, avaliados em ensaios de - D-glucosidase isolada de Sacharomyces cerevisiae. Nestes testes preliminares, o composto 77 foi o mais ativo, o qual foi capaz de inibir a atividade da enzima em 40% a 1mM. Esses resultados encorajam a realização de novos experimentos, principalmente, a determinação de Ki e avaliação da atividade relativa à replicação do vírus HIV. Portanto, a obtenção destes pseudodissacarídeos trouxe uma contribuição importante no que diz respeito à química de carboidratos e também ao tratamento das doenças citadas. / Glucosidases are enzymes that catalyze the hydrolysis of glycosidic bonds releasing monosaccharide units from a non-reducing end of an oligosaccharide or glycoconjugate. Iminosugars are polihydroxilate piperidinic alkaloids isolated from plants (Morus alba) and microorganisms (Bacillus), such as nojirimicin (NJ) (1) and 1- deoxynojirimicin (2), which are described as glucosidase inhibitors. The potential use of these inhibitors in the treatment of viral infection, tumoral growing, metastasis, diabetes, Gaucher´s disease and osteoarthritis has stimulated the scientific community on the search for novel iminosugar derivatives. Thereby, the synthesis of pseudodisaccharides, having both iminosugar and glycopyranose residues, represents an interesting strategy to obtain these derivatives, despite the challenges involved in generating the link between these two sugars. For this reason, we have used click chemistry as a tool to introduce a 1,2,3-triazole bridge between the sugars from the coupling of azide-glycosides with N-propargyl-iminosugar. Thus, the synthesis of N-propargyl-iminosugar (73), containing the terminal acetylene function, was performed in five steps, and was used in the 1,3-dipolar cycloaddition reaction with three glycosidic derivatives containing the azide group at anomeric (C-1), C-3 or C-6 positions. By applying this CuAAC (Copper(I)-catalyzed Azide-Alkyne Cycloaddition), three novel pseudo-disaccharides (77, 81 and 85) were synthesized in moderate yields and then, evaluated in -D-glucosidase assays isolated from Sacharomyces cerevisiae. In these preliminary test, compound 77 was the most active from the series, which was able to inhibit 40% of the enzyme activity at 1 mM. These results encourage us to perform new experiments, notably the determination of Ki and evaluation towards HIV replication. Thus, a contribution regarding carbohydrate chemistry and treatment of the supracited diseases was achieved by the synthesis of these pseudodisaccharides.

Toll like receptors (TLRs) are found on B cells, macrophages, monocytes, and dendritic cells, and these cells belong to the innate immune system that recognizes antigens and induces multiple cell responses through the release of cytokines. TLR1, TLR2 and TLR6 function as heterodimers, either as TLR1/TLR2 or TLR2/TLR6 to recognize lipopeptides. TLR1/2 dimer activation releases inflammatory cytokines, while TLR2/TLR6 dimer activation releases immunomodulatory cytokines. Based on the size of the binding pocket between TLR2 and TLR6, it was hypothesized that lipopeptides, such as FSL1, could be simplified while keeping overall activity. FSL1 is a lipopeptide first isolated from Mycoplasma salivarum that activates macrophages at picomolar concentrations. It is expected that synthetic lipopeptides mimicking immunostimulatory molecules such as FSL1 will allow development of better ways to stimulate or modulate the immune system. Therefore, novel synthetic TLR2/6 ligands were synthesized replacing the polylysine chain with a polyamine chain showing activation of the immune cells in a manner like FSL1. Natural killer T-cell (NKT) antigens, such as α-galactosylceramide (α-GalCer), are carried through the body by lipid transfer proteins before they interact with the NKT cells. Not all the proteins involved in glycolipid transportation have been characterized. The synthesis of an α-GalCer analogue, termed CD1d-Triceps was designed to help find additional proteins involved in glycolipid trafficking. CD1d-Triceps has three functionalities: the first is the α-GalCer structure, and the other two are on C6 of the sugar: biotin, which helps tag the molecule for its purification, and a photoactive tag that, upon UV light activation, will cross-link with neighboring proteins. Antibiotic-resistant strains of Staphylococcus aureus (SA) are a growing health problem worldwide. Serotype 5 and 8 are the most common SA pathogens. Loading the serotype 5 or 8 disaccharides onto Qβ-particles that are linked to an NKT cell activator yield a vaccine that is expected to trigger adaptive immunity to the disaccharide. Previous similar studies showed production of antibodies with high affinity against Streptococcus pyogenes oligosaccharides in a similar vaccine.

The mechanisms of transepithelial absorption of dietary sucrose in the American lobster, Homarus americanus, were investigated in this study to determine whether sugars can be transported across an animal gut intact or as monosaccharides following hydrolysis. Lobster intestine was isolated and mounted in a perfusion chamber to characterize the mechanisms of mucosal to serosal (MS) 14C -sucrose transport across the intestine MS fluxes were measured by adding varying concentrations of 14C-sucrose to the perfusate which resulted in a hyperbolic curve following Michaelis-Menten kinetics. The kinetic constants of the proposed sucrose transporter were KM = 15.84 ± 1.81 µM and Jmax = 2.32 ± 0.07 ρmol cm-2min-1. The accumulation of 14C-sucrose in the bath in the presence of inhibitors, phloretin, phloridzin, and trehalose was observed. Inhibitory analysis showed that phloridzin, an inhibitor of Na+-dependent mucosal glucose transport, decreased MS 14C-sucrose transport suggesting that MS 14C-sucrose radioactive flux may partially involve an SGLT-1-like transporter. Phloretin, a known inhibitor of Na+-independent basolateral glucose transport, decreased MS 14C-sucrose transport, suggesting that some 14C-sucrose radioactivity may be transported to the blood by a GLUT 2-like carrier. Decreased MS 14C-sucrose transport was also observed in the presence of trehalose, a disaccharide containing D-glucose moieties. Thin-layer chromatography (TLC) was used to identify the chemical nature of radioactively labeled sugars in the bath following transport. TLC revealed 14C-sucrose was transported across the intestine largely as an intact molecule with no 14C-glucose or 14C-fructose appearing in the serosal bath or luminal perfusate. Bath samples evaporated to dryness and resuspended disclosed only 15% volatile metabolites. Results of this study strongly suggest that disaccharide sugars can be transported intact across animal intestine and provide support for the occurrence of a disaccharide membrane transporter that has not previously been functionally characterized.