Rating Structures by Agreement with NMR Data
| | | VerifyIt | | | | |

The NMRanalyst VerifyIt module explains the consistency between the NMR data and a proposed molecular structure. VerifyIt rates the consistency based on (1) the observed vs. expected numbers of proton and carbon resonances, (2) the observed vs. expected numbers of methyl- and methoxy-groups, (3) the observed vs. predicted proton and carbon shifts, and (4) the spectral purity rating.

Besides generating a consistency rating, VerifyIt also determines whether a proposed structure explains the observed NMR data better than the millions of structures in the FindIt structure database. VerifyIt reports a placement for the proposed structure relative to all the FindIt structures with regard to how well the structure matches the NMR data. If the candidate structure obtains the place one, which means that it agrees with the specified NMR data better than any of the 8 million FindIt structures, it is a good indication that the candidate structure is likely the correct one.

VerifyIt can assign detected chemical shifts to a proposed structure. To carry out the assignment, the carbon and carbon-bonded proton shifts are predicted for the specified structure. Each predicted shift is then replaced by the closest matching observed shift. As the heteroatom-bonded proton shifts are not predicted, any detected heteroatom-bonded proton shifts are unlikely to match predicted carbon-bonded proton shifts and are simply ignored. Proton-proton couplings complicate the interpretation of multiplets in a proton spectrum. The median frequency of the proton resonance cluster is taken as the observed proton shift value and is assigned based on the closest match to a predicted proton shift. The following figures display the assigned carbon-bonded proton (top) and carbon (bottom) shifts for the taxol structure from the analysis of the 1D proton and carbon spectra of the taxol dataset.

Automated VerifyIt Proton Assignments:

Proton Assignments

Automated VerifyIt Carbon Assignments:

Carbon Assignments

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