Electrochemical behaviour of new electroreducible amphiphilic saccharide derivatives II: Electroreduction in protic media

The electrochemical reduction of new amphiphilic molecules derived from sug ars and aromatic ketones has been performed in protic media under basic and acidic conditions. Exhaustive electrolyses have yielded, regardless of pH, the alcohol resulting from two-electron and two-proton exchanges. No trace of pinacol was detected. This unusual behaviour has been related to the pr operties of the saccharidic moiety, which can favour a highly hindered bent back conformation. The dimerisation reaction is thus less probable. Molecu lar calculations and a dynamic study in aqueous solution have shown that th e less energetic conformations are stabilised by hydrogen bonds between the sugar moiety and the carbonyl group by means of six water molecules, three of them building a solvation chain between the carbonyl function and the p rimary alcohol of the sugar. As a comparison the same calculations, applied to an aprotic solvent (DMF), indicate an extended form for the conformatio n of lowest energy.