One-pot synthesis of glycyrrhetic acid polyglycosides based on grafting-from method using cyclic sulfite

Graphical abstract
Highlights • One-pot synthetic pathway for glycyrrhetic acid polyglycosides was established. • The compounds were prepared via grafting reaction of cyclic sulfite 4 from the aglycon. • Cationic ring-opening polymerization of 4 gave (1 → 2)-linked polysaccharide skeletons. • Polymerization degree of the polymer was moderately controllable. • Thermodynamic parameters for degradation of 4 and glycal epoxide 3 were evaluated.
Glycyrrhetic acid polyglycosides were synthesized in one-pot via cationic ring-opening condensation polymerization of cyclic sulfite (4) initiated by glycyrrhetic acid as an aglycon. Sulfite 4 worked as a practical monomer for the preparation of (1 → 2)-linked polysaccharide skeletons. The chemical stability of 4 was evaluated by the comparison of thermodynamic parameters with those of conventional epoxide (2). The grafting reaction of 4 from glycyrrhetic acid (5) was performed in the presence of TfOH and MS 3A in CH2Cl2 at room temperature. The polymerization degree was moderately controllable by the change of feed ratio of initiator.