Hierarchical Self-Assembly of Amphiphilic ß-C-Glycosylbarbiturates into Multiresponsive Alginate-Like Supramolecular Hydrogel Fibers and Vesicle Hydrogel.

Ordered molecular self-assembly of glycoamphiphiles has been regarded as an attractive, practical and bottom-up approach to obtain stable, structurally well-defined, and functional mimics of natural polysaccharides. This study describes a versatile and rational design of carbohydrate-based hydrogelators through N,N'-substituted barbituric acid-mediated Knoevenagel condensation onto unprotected carbohydrates in water. Amphiphilic N-substituted ß-C-maltosylbarbiturates self-assembled into pH- and calcium-triggered alginate-like supramolecular hydrogel fibers with a multistimuli responsiveness to temperature, pH and competitive metal chelating agent. In addition, amphiphilic N,N'-disubstituted ß-C-maltosylbarbiturates formed vesicle gels in pure water that were scarcely observed for glyco-hydrogelators. Finally, barbituric acid worked as a multitasking group allowing chemoselective ligation onto reducing-end carbohydrates, structural diversity, stimuli-sensitiveness, and supramolecular interactions by hydrogen bonding.

Synthetic Factors Governing Access to Tris(ß-diketimine) Cyclophanes versus Tripodal Tri-ß-aminoenones.

Tris(ß-diketimine) cyclophanes are an important ligand class for investigating cooperative multimetallic interactions of bioinorganic clusters. Discussed herein are the synthetic factors governing access to tris(ß-diketimine) cyclophanes versus tripodal tri-ß-aminoenones. Cyclophanes bearing Me, Et, and MeO cap substituents and ß-Me, Et, or Ph arm substituents are obtained, and a modified condensation method produced α-Me ß-Me cyclophane. These operationally simple procedures produce the ligands in gram quantities and in 22-94% yields.