Direct Conversion of Agarose into Alkyl Mono- and Disaccharide Surfactants Based on 3,6-Anhydro L- and D-Galactose Units

In this work, a new type of agaran-derived non-ionic surfactants has been prepared through the one-pot transformation of agarose into 3,6-anhydro L- and D-galactose acetal monomers and dimers possessing one or two alkyl chains according to the cyclic or open form of the L- and D-galactose units. The two steps process involves the butanolysis of agarose into butyl mono- and disaccharide 3,6-anhydro L- and D-galactose acetals promoted by the presence of Amberlyst-15Dry, followed by the transacetalization with n-dodecanol using the same acid catalyst. The chemical structures of the alkyl mono- and disaccharide surfactants were fully characterized by 1D and 2D NMR experiments. Surface activities of these products in a pure form or as mixtures were investigated depending on their hydrophilicity/hydrophobicity and quite low values of superficial tensions (<27 mN m(-1)) and sunflower seed oil/water interfacial tensions (similar to 5 mN m(-1)) were obtained.

Automated summary

A new type of agaran-derived non-ionic surfactants were prepared by transforming agarose into anhydro L- and D-galactose acetal monomers and dimers with alkyl chains, followed by characterization and investigation of their surface activities, showing low superficial tensions and interfacial tensions.