Comparison of diffusion coefficients for matched pairs of macrocyclic and linear molecules over a drug-like molecular weight range

The diffusion coefficients of a series of closely matched pairs of macrocyclic and linear molecules have been compared using NMR spectroscopy. The macrocyclic series was designed both to overlap with and extend beyond the molecular weight range typically employed for drug-like molecules. The linear molecules each represent a carbogenic fission of their macrocyclic counterparts, designed to minimize differences in functionality and physicochemical properties. Each series of molecules was prepared using copper catalyzed azide-alkyne cycloaddition (CuAAC) reactions conducted in a flow using a copper tube. The macrocyclic series exhibited consistently higher diffusion across the entire molecular weight range studied. The fold difference in diffusion coefficients between the macrocyclic and linear analogues appeared to be independent of either solvent viscosity or dielectric environment.