OLIGOSACCHARIDES AND MOLECULAR RECOGNITION

Carbohydrates have been established as the most abundant – and arguably the most structural diverse – organic molecules found in nature. They are chiral molecules readily available in nature in a variety of diastereomeric forms. Their conformational rigidity provides a well defined three-dimensional spatial arrangement of substituents with various multi-configured hydroxyl groups for chemical modification. Carbohydrates play a fundamental role in signal transduction and vital molecular recognition phenomena, they dominate the landscape of the cell and are responsible for cell-cell interaction, the recognition of virus and bacteria, binding of toxins and are involved in cell growth. For these reasons they are an attractive material for the development of new therapeutic agents, such as their application as antigenic material in vaccines formulation. In this framework we focused our attention in a troublesome nosocomial pathogen: Acinetobacter baumannii, a Gram-negative coccobacillus, in particular on the strain ATCC 17961. We synthesized three different fragments of the O-chain LPS of this bacterium, containing the unusual sugar residue 2,3-diacetamido-2,3- dideoxy-D-glucuronic acid. The binding affinity of these fragments will be evaluated by competitive ELISA assay against the anti-LPS serum of Acinetobacter baumannii ATCC 17961. Furthermore, thanks to chemical flexibility of carbohydrates, they are attractive chiral molecular scaffolds in asymmetric catalysis. They could be employed as metal ligands for enantioselective catalysis or themselves as metal-free organocatalysts. Sugars are an attractive material in this field for their low cost, potential polyfunctionalization, and the possibility to modify the chemical structure of the molecule in order to tune the chemical and physical properties for example the steric hindrance, the electronic and solubility properties of the catalyst. We synthesized two different carbohydrate-based organocatalyst, and we tested their activity in reaction between acetylacetone or diethylmalonate with β-nitrostyrene. e5