Regio- and stereoselective studies of nucleophilic addition reactions to small ring systems and their application to the synthesis of valuable glycoconjugates

Carbohydrate chemistry currently constitutes a “multifaceted” discipline which is strongly connected with both organic and medicinal chemistry. Carbohydrates are important biomolecules whose role is not only limited to energy storage, since they are constituents of glycoproteins, glycolipids, and other conjugates involved in important signaling and structural functions. Recently, studies in our laboratory have indicated α and β vinyl epoxides- and vinyl aziridines-glycal derived as excellent glycosyl donors able to give the corresponding 2,3-unsaturated- β− and α-O-glycosides, respectively, in a new, completely 1,4-regioselective, stereospecific, uncatalyzed and directly substrate-dependent glycosylation process. On these bases, we focused our attention on carbasugars and we moved towards enantioselective synthesis of α and β vinyl epoxides that are the carba analogues of glycal-derived α and β vinyl epoxides and the corresponding N-nosyl aziridines. Studies on reactivity and selectivity in nucleophilic addition reaction of these oxirane systems and elaboration of their 1,2-addition products have made possible the construction of O-linked carbohydrate mimetics and of pseudodisaccharides with a possible pharmacological activity.