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Digital archive of theses discussed at the University of Pisa


Thesis etd-10192023-215716

Thesis type
Tesi di laurea magistrale LM5
Thesis title
Stereoselective synthesis of 1,4- D- gulo disaccharides as ligands for Protein Tyrosine Phosphatase 1B (PTP-1B) ​
Course of study
relatore Prof.ssa Di Bussolo, Valeria
relatore Dott. Di Pietro, Sebastiano
relatore Dott.ssa Santangelo, Maria Chiara
  • Disaccharides
  • stereoselective glycosylation
  • PTP-1B
Graduation session start date
Release date
Among the different mechanisms used by cells to control regulatory processes, protein phosphorylation and dephosphorylation is one of the most important. This reversible mechanism consists of the addition or abstraction of a phosphate group to various amino acid residues by a protein kinase (PK) or phosphatase (PP), respectively, triggering a conformational change that modulates the activity of the target protein.
Protein tyrosine phosphatase 1B (PTP1B), belonging to the PTP family, is considered a direct negative regulator of numerous receptor and receptor-associated tyrosine kinases. This enzyme localized on the cytoplasmic side of the endoplasmic reticulum of several tissues such as liver, adipose tissue, skeletal muscle, and brain is involved in the pathophysiology of several diseases. More recently, PTP1B has attracted attention in the field of neuroscience. Indeed, its inhibition has been shown to prevent microglial activation, thus exerting a potent anti-inflammatory effect, and it has also shown the potential to enhance cognition through hippocampal insulin stimulation, leptin and insulin. As a result, most research on the clinical efficacy of targeting PTP1B has been developed in the field of obesity and type 2 diabetes mellitus (TD2M).
Crystallographic structures of the protein show the presence of hydrophilic active sites containing Cys and Arg residues, despite this, several allosteric sites on the protein also demonstrate affinity towards lipophilic ligands. The different degrees of hydrophilicity and lipophilicity of the allosteric sites allows the use of heterogeneous ligands.
In this regard, the aim of my thesis work has been focused on the synthesis of linear 1,4-stereodefined disaccharides with different degree of polarity and their evaluation as ligands of PTP1B.
Recently, our research group identified a microwave-activated one-pot reiterative assembly of glycal-derived vinyl epoxides, that allow a substrate-dependent non-catalyzed stereospecific process for the preparation of both β-1,4-D –Gulo- and α-1,4- D-Manno-oligosaccharides. The general procedure involves the addition of the glycosyl donor vinyl epoxide 1β, generated in situ by cyclization under basic conditions for t-BuOK of its stable precursor hydroxy mesylate, to a series of previously synthesized glycosyl acceptors such as which therefore represent the first unit.
The distribution of oligosaccharides resulting from the process depends on the relative ratio between the initiator and the vinyl epoxide 1β. For the synthesis of the disaccharide, we used 2.5 equivalents of initiator and 1 equivalent of vinyl epoxide 1β.
Disaccharide was then treated with OsO4 in presence of NMO to afford the dehydroxylated disaccharide, then deprotected in a reducing environment to provide the most hydrophilic disaccharide.
The advantage of this procedure is to easily assess the 2,3-unsaturated-1,4-disaccharides without any protection/deprotection/activation protocol and to allows the possibility of increase the lipophilicity of the molecules by subsequent functionalization, in order to test them as PTP1B ligands.
Ongoing, in vitro evaluations of these compounds demonstrated their possible use as ligands for the PTP1B protein.