Synthesis of linear and cyclic polyglycerols. Polyglyceryled surfactants: synthesis and characterization

Glycerol is one of the main by-products of oleochemistry. In order to develop the possible uses of this by-product, research can focus on the production of polyglycerols and their non-ionic surfactants. However, they are usually prepared under drastic conditions (caustic media and high temperatures) leading to complex mixtures of undefined oligomers. In this context, a European Program started to prepare authentic standards of oligomers of glycerol as well as corresponding surfactants and to establish relations between structures and activity. This work describes a new means of access to authentic standards of linear and cyclic oligoglycerols and their mono-esters or mono-ethers with well-defined structures and determined degrees of polymerisation from 2 to 5, through short and efficient syntheses allowing further scaling up. On the one hand, linear oligomers were obtained by means of a convergent approach based on regioselective opening of epoxides. lodocyclisation reactions involving unsaturated alcohols permitted to build cyclic diglycerols, whereas larger cycles were prepared thanks to the condensation of two linear fragments. On the other hand, the use of orthogonal protective groups and of selective reactions yielded a large range of amphiphilic molecules bearing different kind of fatty chain (length, unsaturations, position on the polar head, ester or ether bond).