Synthesis and conformational analysis of novel water soluble macrocycles incorporating carbohydrates, including a β-cyclodextrin mimic

Rigid macrocyclic scaffolds based on carbohydrates have potential for the display of recognition groups with defined 3D structure and may have application in bioorganic and supramolecular chemistry. A series of water soluble macrocyclic structures containing two saccharide units was synthesised by ring closing metathesis of allyl and pentenyl glycosides derived from glucuronic acid. The 3D structure of the constrained systems was explored by NMR and computational methods. CD spectra were also recorded. On the basis of experimental observations we suggest that the carbohydrate presentation is constrained into a U-shape for the smaller ring size but can access an S-shape arrangement in the larger macrocycle. As an extension it is shown that the larger macrocycle displayed phenomena similar to β-cyclodextrin (β-CD). The binding of 8-anilino-1-naphthalenesulfonate (ANS) to β-CD is detectable by reversal of quenching of the ANS emission spectrum and a similar reversal of quenching was observed when this macrocycle was added to a solution of ANS; this was further supported by NMR. Furthermore molecular modelling suggests that the macrocyclic scaffolding has potential for the development of peptidomimetics.