significantly underutilized. In our own work we have found that 13C spectroscopy is a more powerful tool than IH NMR spectroscopy, especially for probing subtle stereochemical questions in complicated systems. This is especially true in five membered ring compounds where IH NMR is at a particular disadvantage. The two techniques can be used independently to solve the same question-that of stereochemistry - but they do so in different ways. Advantage can be taken in IH NMR of a relatively consistent relationship between stereochemical orientation and coupling constants between vicinal protons, while in 13C NMR it is the correlation between spatial relationships of non-hydrogen, y substituents and their effect on chemical shift that can be used to assign stereochemistry. It was also clear that the use of 13C NMR required a different approach to problem solving than that typically used with IH NMR. While the latter technique could be employed with a very general approach (e.g., the Karplus equation), 13C NMR would, at least for the immediate future, require a relatively extensive set of model systems from which the consequences of stereochemical changes could be derived for any given carbon framework.

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