Direct Assignment of the Relative Configuration in 1,3,n-Methyl-Branched Carbon Chains by 1H NMR Spectroscopy

On the basis of the assignment of methylene proton signals in (1)H NMR and determination of the chemical shift difference (Deltadelta), the relative configuration of 1,3,n-methyl-branched deoxypropionates can be determined directly. Comparison of the chemical shifts in the corresponding syn- and anti-configured compound pairs shows remarkable differences, while the absolute values depend on the presence and nature of adjacent functional groups. The determination of the Deltadelta values provides a reliable assessment of the relative configuration in 1,3,n-methyl-branched polypropionate chains and is even valid for macrocycles.