Complexation-driven assembly of imine-linked helical receptors showing adaptive folding and temperature-dependent guest selection

Abstract

The development of synthetic receptors capable of selectively binding guests with diverse structures and multiple functional groups poses a significant challenge. Here, we present the efficient assembly of foldamer-based receptors for monosaccharides, utilising the principles of complexation-induced equilibrium shifting and adaptive folding. Diimine 4 can be quantitatively assembled from smaller components when d-galactose is added as a guest among monosaccharides we examined. During this assembly, dual complexation-induced equilibrium shifts toward both the formation of diimine 4 and the conversion of d-galactose into α-d-galactofuranose are observed. Diimine 6 is quantitatively assembled in the presence of two different guests, methyl β-d-glucopyranoside and methyl β-d-galactopyranoside, resulting in the formation of two dimeric complexes: (6-MP)2⊃(methyl β-d-glucopyranoside)2 and (6-MM)2⊃(methyl β-d-galactopyranoside∙2H2O)2, respectively. These two complexes exhibit distinct folding structures with domain-swapping cavities depending on the bound guest and temperature. Interestingly, (6-MM)2⊃(methyl β-d-galactopyranoside∙2H2O)2 is exclusively formed at lower temperatures, while (6-MP)2⊃(methyl β-d-glucopyranoside)2 is only formed at higher temperatures.