NMR Assignments and Molecular Modeling -- Approaches to Structures and Conformational Analysis of Natural Products

NWR spectra are very important tool in the structure elucidations, such as 1H-1H COSY for either two bonds or long range coupling may be emphasized, nOe and its related techniques give the informations of proximate proton—proton relationship and HETCOR provide the correlations between a carbon and its attached proton(s). But the assignments of quarternary carbons are very important in the structure determinations, because they divide the whole molecule into the isolate parts. the selective INEPT, FLOCK and related techniques are the more efficient method to establish the relationship between different parts in the molecule via long range HETCOR techniques.