An analysis strategy based on the concerted application of several two-dimensional NMR experiments, such as gCOSY, 1D and 2D TOCSY, gHSQC, gHMBC and gHSQC-TOCSY for 1 provided unequivocal confirmation of the structure. The proton connectivities were identified from the COSY and 1D/2D TOCSY spectra; the gHETCOR and gHSQC correlations were used to confirm the proton bearing carbons (CH?s) and gHMBC cross peaks was used to define the locations of the quaternary carbons. The assigned 1H and 13C NMR data are listed on the structure formula. The spin-spin coupling constants between protons of the A-D rings were deduced from the calculated spectra (see Table).
Additionally, the gradient selected gHSQC-TOCSY spectra were obtained at different mixing times (36 and 80 msec) to identify the spin system. In other words, this experiment gave simultaneously assignment of 1H and 13C chemical shifts for each ring (A-D).
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C. Eugene Bennett
Department of Chemistry
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West Virginia University
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