Easy access to a carbohydrate-based template for stimuli-responsive surfactants

Thomas Holmstrøm,Daniel Raydan,Christian Marcus Pedersen

doi:10.3762/bjoc.16.229

Abstract

In this paper we describe the synthesis of a new carbohydrate-based building block functionalized with azido or amino groups on the 2 and 4 positions. The building block can be synthesized in anomerically pure form in only five scalable steps starting from commercially available levoglucosan. It was shown that the building block could undergo alkylations under strongly basic conditions. The building block with azido groups could furthermore take part in CuAAC reactions, generating derivatives with ester or carboxylic acid functionalities. In addition, the anomeric mixture of the building block was used for the synthesis of a molecule that could act as an emulsifier only in the presence of Zn2+ ions.

Highlights

Surfactants are molecules with both a hydrophilic and a lipophilic domain, thereby rendering them amphiphilic
In this paper we describe the synthesis of a new carbohydrate-based building block functionalized with azido or amino groups on the 2 and 4 positions
The anomeric mixture of the building block was used for the synthesis of a molecule that could act as an emulsifier only in the presence of Zn2+ ions

Summary

Introduction

Surfactants (surface-active agents) are molecules with both a hydrophilic and a lipophilic domain, thereby rendering them amphiphilic. The conformational change of the head group acts as a mechanical impulse that can increase or decrease the distance between the two lipophilic tails, changing the amphiphilic properties of the molecule Incorporating such molecules into the lipid bilayer of liposomes can result in the decomposition of the whole liposome when the stimuli-responsive surfactants are triggered, thereby releasing the cargo [8]. Guo and co-workers have earlier succeeded with the use of pH-sensitive surfactants and even introduced the term “flipids” for such pH-responsive lipids [7,8] This term could describe compounds where the binding of a guest molecule is able to change the conformation of the head group, for example, through a ring flip giving rise to an altered amphiphilicity. Levoglucosan is the ideal starting material for such transformations as the 2- and 4-positions can be functionalized with high regioselectivity via the Černý epoxide [20]

Results and Discussion

Evaluation of amphiphilic properties

Conclusion