Stereochemical investigation of flexible macrocyclic cembranes depending on residual dipolar couplings method

It is a great challenge to unambiguously validate stereochemistry for flexible macrocyclic compounds, such as cembrane diterpenoids. In the present study, the feasibility of residual dipolar couplings (RDCs) method is verified using ten cembranes with the configurations confirmed by X-ray diffraction. The result showed that the application of RDCs is reliable for the stereochemical elucidation of most compounds. But it is less determination for the stereochemistry of some other compounds. Nevertheless, a new idea was provided that the reconstructed correlation data which was processed by tick out the flexible fragments in superimposed conformers, which relied on the occasioned problem that the correct configuration should have the best agreement with the experimental result for RDCs.