Saccharide Induction of Chiral Orientation of the Aggregate Formed from Boronic-Acid-Appended Amphiphiles

A boronic-acid-appended amphiphile bearing an azobenzene chromophore at the chain center, N-[4-(dihydroxyboryl)benzyl]-N-(10-{4-[(4-dodecyloxyphenyl)azo)]phenoxy}decyl)- N,N-dimethylammonium bromide (4) was synthesized. In aqueous media, compound 4 formed a scarcely-oriented aggregate in the absence of saccharides, but in the presence of saccharides the boronic acid groups formed saccharide complexes and the resultant amphiphiles formed well-ordered aggregates. The ΔH value in DSC depended on the inherent structure of the added saccharides. Although D-glucose and methyl α-D-glucopyranoside could only form less ordered aggregates, D-fructose and D-xylose formed well-ordered aggregates. The saccharide complexes with 4 became CD-active with the appearance of exciton-coupling bands inherent to the saccharides. The CD band intensity was increased with increasing saccharide concentration but decreased by a further increase in the saccharide concentration. These results indicate that the reversible boronic acid-saccharide interaction is useful to induce the chirality in the ordered aggregate structure, where saccharides are used as a trigger for the chiral induction.