Skeletal Structure Connectivities of Atoms

Additional partial structures Ib-f (Table 10) are detected by two-dimensional CH-correlation experiments using pulse sequences adjusted to the much smaller CH coupling constants of C and H nuclei separated by two, three, or more bonds. Such experiments are known as the CH COLOC with detection (Fig. 9) or as the more sensitively H detected and therefore less time-consuming HC HMBC. Contour plots of these experiments (Fig. 9) permit the localization of carbon atoms two or three bonds apart from a certain proton. Thus, the methyl protons with Sh 2.02 in Fig. 9 display eross signals with the earbon nuclei at 8c = 170.5 and 8c = 68.8. 

To conclude, this methyl group belongs to an acetoxy function attached to the carbon with 5c = 68.8 (Table 10, partial strueture 1d). 

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