Stereoselective synthesis of a Glc-NAc conjugate as potential modulator of carbohydrate metabolism and Regio- and stereoselective behaviour of carbapyranose 1,2-epoxides with α-gluco and β-manno configuration

The first part of the present work thesis concerns the synthesis of a Glc-NAc-Conjugated Lactate Dehydrogenase Inhibitor as promising anticancer agent. It was widely demonstrated that solid tumors have an enormous consumption of glucose and are characterized by a “metabolic switch”, because tumor cells use as principal source of energy aerobic glycolysis, instead of oxidative phosphorylation. Besides, cancer cells overexpress the glucose transporter GLUT-1 and enzymes of glycolysis, including Lactate Dehydrogenase Isoform A (LDH-A), which has recently emerged as a new potential target in the anticancer therapy, because of its key role in glycolysis progression. On the basis of these evidences, N-hydroxyindole-based (NHI) LDH-A inhibitors were synthesized in our Department. Recently the research team where I carried out my thesis converted one of these NHI-based LDH-A inhibitors into the corresponding glucose-conjugate and the preliminary studies on its anticancer activity demonstrated that this activity depends on a dual-targeting mechanism, which involves both LDH-A and glucose transporter GLUT-1. On account of this, our goal was synthesizing the corresponding Glc-NAc-conjugate, since the N-acetylglucosamine group, as reported, plays a very important biological role and appears to be involved in determining some features of cancer cells. The second part of this work thesis concerns regioselective studies of the nucleophilic addition reactions to carbapyranose-1,2-epoxide with α-gluco and β-manno configuration. Ring-opening reactions of carbapyranose-1,2-epoxide with β-manno configuration had been widely studied because these epoxides were opened efficiently with attack at C(1) (sterically and electronically favoured) to give 1,2-trans-diaxial carba-α-manno derivatives with both oxygen and nitrogen nucleophiles. Instead carbapyranose-1,2-epoxide with α-gluco configuration did not give such good results, because nucleophiles attack was often unregioselective. Precedent studies, finalyzed to the synthesis of useful α-manno glycoconjugates confirmed these kinds of behaviour, besides in our studies on epoxides with α-gluco configuration it was observed an undesired intramolecular addition process with the internal nucleophile C(5)-CH2OR, that allows the formation of a bicyclic byproduct. The first goal of my thesis was to minimize or to avoid the formation of this bicyclic byproduct, in order to better study and direct the stereo- and regioselectivity of nucleophilic addition reaction on these substrates. For these reasons, first we introduced different bulky protecting groups on the C(6) position, then, we introduced a deoxy-methyl group on C(6) position. On the one hand, introduction of bulky protective groups on C(6) position still have not allowed to obtain regioselective results in nucleophilic addition reactions with O-nucleophiles, however reduced formation of the bicyclic compound was achieved. On the other hand, the introduction of a methyl substituent on C(5) position completely avoids the formation of the bicyclic compound but still affords unregioselective results in nucleophilic addition reactions. More interesting, the use of alcohols different from MeOH efficiently influences the regio- and stereoselectivity of the ring opening process. A very nice result was obtained under methanolysis using LiClO4 as the coordinating agent: in these reaction conditions we observed a completely C(1) regio- and stereoselective nucleophilic addition process

Synthesis and biological evaluation of non-glucose glycoconjugated N-hydroyxindole class LDH inhibitors as anticancer agents

Inhibitors of human lactate dehydrogenase A (LDH-A) are promising therapeutic agents against cancer. The development of LDH-A inhibitors that possess cellular activities has so far proved to be particularly challenging, since the enzyme’s active site is narrow and highly polar. In the recent past, we were able to develop a glucose-conjugated N-hydroxyindole-based LDH-A inhibitor designed to exploit the sugar avidity expressed by cancer cells (the Warburg effect). Herein we describe a structural modulation of the sugar moiety of this class of inhibitors, with the insertion of α-D-mannose, β-D-gulose, or β-N-acetyl-D-glucosamine portions in their structures. Their stereospecific chemical synthesis, which involve a substrate-dependent stereospecific glycosylation step, and their biological activity in reducing lactate production and proliferation in cancer cells are reported. Interestingly, the α-D-mannose conjugate displayed the best properties in the cellular assays, demonstrating an efficient antiglycolytic and antiproliferative activity in cancer cells

Polysaccharides’ Structures and Functions in Biofilm Architecture of Antimicrobial-Resistant (AMR) Pathogens

Bacteria and fungi have developed resistance to the existing therapies such as antibiotics and antifungal drugs, and multiple mechanisms are mediating this resistance. Among these, the formation of an extracellular matrix embedding different bacterial cells, called biofilm, is an effective strategy through which bacterial and fungal cells are establishing a relationship in a unique environment. The biofilm provides them the possibility to transfer genes conferring resistance, to prevent them from desiccation and to impede the penetration of antibiotics or antifungal drugs. Biofilms are formed of several constituents including extracellular DNA, proteins and polysaccharides. Depending on the bacteria, different polysaccharides form the biofilm matrix in different microorganisms, some of them involved in the first stage of cells’ attachment to surfaces and to each other, and some responsible for giving the biofilm structure resistance and stability. In this review, we describe the structure and the role of different polysaccharides in bacterial and fungal biofilms, we revise the analytical methods to characterize them quantitatively and qualitatively and finally we provide an overview of potential new antimicrobial therapies able to inhibit biofilm formation by targeting exopolysaccharides

Retaining the structural integrity of disulfide bonds in diphtheria toxoid carrier protein is crucial for the effectiveness of glycoconjugate vaccine candidates.

The introduction of glycoconjugate vaccines marks an important point in the fight against various infectious diseases. The covalent conjugation of relevant polysaccharide antigens to immunogenic carrier proteins enables the induction of a long-lasting and robust IgG antibody response, which is not observed for pure polysaccharide vaccines. Although there has been remarkable progress in the development of glycoconjugate vaccines, many crucial parameters remain poorly understood. In particular, the influence of the conjugation site and strategy on the immunogenic properties of the final glycoconjugate vaccine is the focus of intense research. Here, we present a comparison of two cysteine selective conjugation strategies, elucidating the impact of both modifications on the structural integrity of the carrier protein, as well as on the immunogenic properties of the resulting glycoconjugate vaccine candidates. Our work suggests that conjugation chemistries impairing structurally relevant elements of the protein carrier, such as disulfide bonds, can have a dramatic effect on protein immunogenicity

ILC Reference Design Report Volume 1 - Executive Summary

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2s^-1. This report is the Executive Summary (Volume I) of the four volume Reference Design Report. It gives an overview of the physics at the ILC, the accelerator design and value estimate, the detector concepts, and the next steps towards project realization.The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2s^-1. This report is the Executive Summary (Volume I) of the four volume Reference Design Report. It gives an overview of the physics at the ILC, the accelerator design and value estimate, the detector concepts, and the next steps towards project realization

ILC Reference Design Report Volume 4 - Detectors

This report, Volume IV of the International Linear Collider Reference Design Report, describes the detectors which will record and measure the charged and neutral particles produced in the ILC's high energy e+e- collisions. The physics of the ILC, and the environment of the machine-detector interface, pose new challenges for detector design. Several conceptual designs for the detector promise the needed performance, and ongoing detector R&D is addressing the outstanding technological issues. Two such detectors, operating in push-pull mode, perfectly instrument the ILC interaction region, and access the full potential of ILC physics.This report, Volume IV of the International Linear Collider Reference Design Report, describes the detectors which will record and measure the charged and neutral particles produced in the ILC's high energy e+e- collisions. The physics of the ILC, and the environment of the machine-detector interface, pose new challenges for detector design. Several conceptual designs for the detector promise the needed performance, and ongoing detector R&D is addressing the outstanding technological issues. Two such detectors, operating in push-pull mode, perfectly instrument the ILC interaction region, and access the full potential of ILC physics

ILC Reference Design Report Volume 3 - Accelerator

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC.The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC

International Linear Collider Reference Design Report Volume 2: PHYSICS AT THE ILC

This article reviews the physics case for the ILC. Baseline running at 500 GeV as well as possible upgrades and options are discussed. The opportunities on Standard Model physics, Higgs physics, Supersymmetry and alternative theories beyond the Standard Model are described.This article reviews the physics case for the ILC. Baseline running at 500 GeV as well as possible upgrades and options are discussed. The opportunities on Standard Model physics, Higgs physics, Supersymmetry and alternative theories beyond the Standard Model are described