Caryophyllene Oxide DQF-COSY

The exocyclic olefinic methylene protons show obvious COSY correlations to one another. In addition, we note weak cross peaks between the olefinic protons at 4.86 and 4.97 ppm and an apparent diastereotopic methylene group (2.11 and 2.37 ppm) and a quartet at 2.60 ppm, respectively. These interactions are reminiscent of the long-range allylic coupling that we saw in ipsenol we could assign these correlations to the diastereotopic methylene C-7 and the methine at C-9. For now, we will be cautious and conservative, and return to this point later in the chapter. 

A look at the extreme low-frequency portion of this COSY spectrum reveals an unexpected interaction. It seems that either one or both of the methyl singlets shows coupling to resonances at 1.65 and at 2.09 ppm. 

This apparent conflict can be resolved by a close examination of the methyl singlets at about 0.98 ppm. There is an unusually low-frequency multiplet, partially buried by the methyl singlets, which we had initially overlooked. This type of unexpected dividend is common in correlation spectra both partially and completely obscured resonances usually reveal themselves in 2-D spectra (see HMQC below). Before continuing our discussion of caryophyllene oxide, let us consider H—13C correlations and how H— H correlations interplay with H—13C correlations. 

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