CO2 as versatile carbonation agent of glycosides: Synthesis of 5- and 6-membered cyclic glycocarbonates and investigation of their ring-opening.

This study demonstrates the successful use of CO 2 as versatile carbonation agent for the synthesis of 5-membered and 6-membered bicyclic glycocarbonates from methyl α- d -mannopyranoside (MDM) and methyl α- d -galactopyranoside (MDG). On the one hand, these two sugars were cyclized into 5-membered glycocarbonates by mere reaction of CO 2 with their hydroxyls either at cis-2,3 or cis-3,4 positions and without resorting to phosgene or its derivatives. The reactivity of the obtained 5-membered cyclic glycocarbonates were further tested with hexyl- and dodecyl amine. The self-assembling behavior of the formed alkyl glycosides in water was investigated and characterized by transmission electron microscope (TEM). On the other hand, secondary hydroxyls at 2- and 3- positions in MDM and MDG were first protected by a ketal group and by two ether, respectively before subjecting their respective 6-position hydroxyl to bromination. Their respective 6-bromo and 4-hydroxyl functions were subsequently reacted in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and CO 2 . The resulting 6-membered cyclic glycocarbonates were then polymerized using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) or DBU as organocatalyst. All the synthesized 5- and 6-membered cyclic glycocarbonates and polyglycocarbonates were thoroughly characterized by FT-IR, 1 H, 13 C NMR and MALDI-ToF and Gel Permeation Chromatography (GPC). [ABSTRACT FROM AUTHOR]