Synthesis of Cross-Linked Glycopeptides and Ureas by a Mechanochemical, Solvent-Free Reaction and Determination of Their Structural Properties by TEM and X-ray Crystallography

A highly efficient and cost-effective green method for the synthesis of complex glycopeptides and ureas mediated by carbonyl diimidazole under solvent-free conditions is reported. The reactions could be performed conveniently in a planetary ball mill by dry grinding, and the isolation of the novel sugar derivatives thus produced could be very efficiently achieved by size exclusion chromatography with environmentally benign substances. A diacetone galactose based diamide, upon crystallization, could be examined by X-ray crystallography and was found to possess a heart-shaped structure. Although the 4-aminophenyl galactoside based diamide synthesized formed spherical particles, the alanine-based diamide formed nanofilamentous/-tubular structures as analyzed by TEM imaging.