Structure Elucidation of a Regioisomer and Another Proton-Deficient Breitfussin Analogue Using Anisotropic NMR.

Determination of the correct 3D structure of regioisomers and other proton-deficient molecules such as the breitfussin analogue is a very challenging task. In the current work, we present the structural differentiation between the two regioisomeric forms of a spiro compound using anisotropic NMR data measured in graphene oxide derivatized cyclopentylamine liquid crystal. The constitution of the regioisomer was first derived from various 2D isotropic NMR data using CASE software, from which other possible regioisomer was generated. Finally, the correct 3D structure is obtained from the anisotropic NMR data, which is also further corroborated with DP4 and DP4+ analysis. We also investigated one proton-deficient breitfussin structural analogue. Finally, results obtained from the anisotropic NMR and DP4+ analysis were compared.