Incredible natural abundance double assignment

Whereas the structural assignment by one-dimensional 13C NMR spectroscopy is unambiguous in the case of D2-Cj(,2,51 Achiba and co-workers were able to determine the carbon atom connectivity by 2D 13C NMR INADEQUATE (incredible natural abundance double-quantum transfer experiment) analysis performed on an isotopically enriched sample (20% 13C).58 In particular, they found that the observed chemical shifts correlate well with the curvature of the spheroid, the more strongly pyramidalized carbon atoms being shifted toward lower magnetic field. 

It is possible to generate more information rich spectra by the introduction of a second frequency dimension. Correlated two-dimensional experiments have recently been developed to extend the assignment process of solid state spectra. For instance, the solution state experiment INADEQUATE (Incredible natural abundance double quantum transfer experiment) which shows direct connectivities based on (essentially a COSY) has been found applicability for the solid state at natural C abundance [227]. 

MAS NMR spectra of a (anhydrous) and (3 (dihydrate) forms of testosterone were recorded. The aliphatic region of the spectrum for the a form of testosterone showed the doublet lines assigned to the two independent molecules by an incredible natural abundance double quantum transfer experiment (INADEQUATE) combined with computation of the chemical shifts of the two forms. 

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