Adamantane-retropeptides, new building blocks for molecular channels

Novel adamantane-oxalamide derivatives, N,N′-bis(1-adamantylglycine methyl ester)oxalamide (meso-1 and rac-1), N,N′-bis(3-aminoadamantane-1-carboxylic acid methyl ester)oxalamide (2) and N,N′-bis(3-aminoadamantane-1-carboxylic acid)oxalamide (3) were prepared and structurally characterized by spectroscopic methods and X-ray analysis. Crystal packing of the structures meso-1 and rac-1 is defined by one-dimensional α-networks of hydrogen-bonded chains. The crystal structures of 2 and 3 are characterized by two-dimensional β-networks of hydrogen bonds. The oxalamide 3 crystallizes as the solvates only. In the crystal structure of 3 the protic solvent participates in hydrogen bonding with the oxalamide moieties. However, in non-protic solvents 3 crystallizes as a solvate but the solvent does not participate in hydrogen bonding. The two-dimensional network of hydrogen bonds connecting molecules of 3 generates channels, which are filled by discrete solvent molecules.