Spacer-mediated synthesis of bis-spiroketal disaccharides: Nonsymmetrical furanose-pyranose difructose dianhydrides

Abstract

The stereochemical outcome of the dimerization reaction of D-fructose, leading to tricyclic bis-spiroketal systems, can be tuned by inserting a xylylene template between the reacting moieties. Spirocyclization becomes then an intramolecular process, the available conformational space depending on the nature of the tether. The methodology is here illustrated by the stereoselective synthesis of two nonsymmetrical di-D-fructose dianhydrides present in commercial caramel