NMRanalyst Sample Application
Structure Elucidation Without 1D Carbon Spectrum
1D Proton Spectrum
|Most likely structure (out of 4 possible ones) by agreement with carbon chemical shift prediction|
Verbenol is a monoterpenoid pheromone.
The verbenol datasets were our first application of using indirect detection spectra. We used to base structure elucidations on a 1D carbon and a 2D INADEQUATE spectrum. Indirect detection methods gain an order of magnitude in sensitivity. But we continued to use the 1D carbon spectrum which is the least sensitive spectrum by now. Eliminating it completes our goal of indirect detection. Several insights result:
It greatly simplifies the structure elucidation when all spectra are acquired with consistent referencing (not the case for this sample). The next best approach is to use the 1D carbon spectrum to adjust the carbon referencing of all spectra. Here it was necessary to use the exhaustive HSQC and HMBC F1 mapping results for referencing corrections. This is tedious and acquiring datasets with consistent referencing is preferable.
Strong ridges at the TMS (0 ppm) and the three methyl carbon frequencies show in the regular HMBC. Adjustment of the single "Ridge" parameter excludes ridge misinterpretations as shown. It would be preferable to acquire this spectrum with Pulse Field Gradient support to simplify the spectral analysis.
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