The COSY Technique

When we obtain the splitting patterns for a particular proton and interpret it in terms of the numbers of protons located on adjacent carbons, we are using only one of the ways in which NMR spectroscopy can be applied to a structure proof problem. We may also know that a certain proton has two equivalent protons nearby that are coupled with a J value of 4 Hz, another nearby proton coupled with a / value of 10 Hz, and three others nearby that are coupled by 2 Hz. This gives a very rich 

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The 300 MHz XH NMR spectra of the all- isomers of 67-72 were measured in CDCI3. The signals were assigned using the COSY technique. The chemical shift values and the values of the coupling constants are completely in agreement with their all-trans structures and are summarized in Tables 19 and 20, respectively, together with the values for 66 which are included for comparison. 

NMR spectroscopy on nuclei in 2-aminopyrans, in many cases, fail to report shifts with a reference, or are assigned inaccurately (86H(24)935). Some examples of chemical shifts and references are given below the data for pyran 19 have been proven by the COSY technique (02X953). One paper (85MI2) was devoted to a comparative analysis of the spectra of pyrans 16, 17, as well as of those of a 2,6-dimethyl-4H-pyran analog. 

Figure 2.45 (282) shows the 2D-NOE spectrum of aphanamol-I. The proton assignments were accomplished by the COSY technique. The 2D-NOE method was then used to determine the conformation of the molecule. The cross-peak 4-11 indicates the 5- and 7-membered rings are cis-linked cross-peak 3-5 shows the isopropyl group to have a yff-configuration and the 8)8-11 peak suggests that the 7-membered ring adopts the conformation shown. 

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