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Tesi etd-05162017-095350

Thesis type
Tesi di laurea magistrale LM5
Regio- and stereoselective control of the ring-opening of carbapyranose 1,2-epoxide with α-gluco configuration under chelating conditions
Corso di studi
relatore Prof.ssa Di Bussolo, Valeria
relatore Bordoni, Vittorio
Parole chiave
  • chelating process
  • carba-epoxides
  • ionic liquids
Data inizio appello
Riassunto analitico
Carbapyranose 1,2-epoxides have been extensively studied as “glicosyl-donor mimics”, in that the epoxide opening reactions can be used to form ether-linked pseudosaccharides and pseudodisaccharides[1].<br><br>Ring-opening reactions of carbapyranose 1,2-epoxides with β-manno configuration had been widely studied because these type of epoxides were opened efficiently with attack at C(1), which is sterically and electronically favoured, to give 1,2-trans-diaxial carba-α-manno derivatives with both O- and N-nucleophiles. Instead carbapyranose 1,2-epoxide with α-gluco configuration didn’t provide good results, because nucleophilic attack was often unregioselective. <br>Despite of this, carbapyranose 1,2-epoxides with α-gluco configuration turn out to be very useful for the synthesis of pseudosaccharides and pseudodisaccharides with pseudo-gluco configuration on carbapyranose unit. <br><br>In my thesis work I have synthesized carbapyranose 1,2-epoxides (1.2) starting from the commercially available tri-O-acetyl-D-glucal (1.1) and I have studied the regiochemical behaviour of this epoxide under different reaction conditions in order to direct the ring-opening process. <br><br><br> <br> 1.1 1.2 <br><br>Synthesis of 1,2-epoxide with α-gluco configuration<br><br>I verified that a completely C(1) regio- and stereoselective nucleophilic addition process, with the exclusive formation of the C(1) regioisomer, occurs under methanolysis using LiClO4 as the coordinating agent. <br><br>On this basis, I have used some ionic liquids as solvent, containing a Li+ cation, in order to promote the coordination effect and to permit a regio- and stereoselective ring-opening process with different nucleophiles.<br>G4TFSI[2], synthesized in the laboratory of prof. Chiappe, turned out to be the most efficient ionic liquid to direct the ring-opening process and to permit the regio- and stereoselective formation of C(1) adducts which correspond to pseuodoglycosides 1.3 with β-gluco configuration.<br><br><br> <br> G4TFSI 1.3<br><br><br><br><br>References:<br><br>1. Roscales, S.; Plumet, J. International Journal of Carbohydrate Chemistry 2016, 1<br>2. Eyckens, D. J.; Champion, M. E.; Fox, B. L.; Yoganantharajah, P.; Gibert, Y.; Welton, T.; Henderson, L. C., Eur. J. Org. Chem., 2016, 913-917.<br>