Convenient Synthesis of a Galacturonic Acid Based Macrocycle with Potential Copper-Complexation Ability

A convenient approach to the construction of a galacturonic acid based macrocycle containing an amide group and a triazole ring has been achieved. The key step relies on the efficient formation of a 16-membered ring by a copper-catalysed intramolecular cycloaddition reaction applied to analkyne-azide galacturonate. Depending on the reaction conditions, the outcome of the 1,3-dipolar cycloaddition varied; the expected intramolecular 1,4-triazole was obtained as well as a C2-symmetric dimer in different ratios. A preliminary study of the complexation properties of this macrocycle towards CuII cations revealed the formation of cryptates in a 1:1 metal/ligand ratio.