NMRShiftDB is an open source collection of chemical structures and their associated NMR shift assignments. The database is generated as a result of contributions by the public and currently contains 19,958 structures with 214,136 assigned carbon chemical shifts. Turns out, it is also a GREAT resource for evaluating the accuracy of NMR predictions.
Several weeks ago, Wolfgang Robien performed a quality check of the NMRShiftDB by comparing the experimental values posted in this database with the CSEARCH prediction algorithm. This algorithm is currently in use in NMRPredict, a commercial product provided by Modgraph Consultants Ltd.
By sharing the results of his study online, we were then able to compare the performance of these algorithms directly with the prediction algorithms within ACD/CNMR Predictor.
The details can be found in the document at the bottom of this entry but the conclusions are very easy to make. Using what we believe is an unbiased, statistically relevant dataset with sufficient structural diversity, ACD/CNMR Predictor vastly outperforms the prediction accuracy of the CSEARCH algorithm. The average deviation in ACD/CNMR predictor was 1.59 ppm compared to an average deviation of 2.22 ppm in CSEARCH.
The document also highlights a separate validation study we performed that considers the degree of overlap between the structures in the training set of ACD/CNMR Predictor with the validation set of NMRShiftDB. This study provides a true measure of the performance of ACD/CNMR Predictor for novel chemical shifts. A similar study of this nature was not conducted by Robien (at least not publicized to date), so we are unaware of the degree of overlap or the accuracy of his predictions on novel chemical shifts.
Download the PDF document here. (Updated July 5th, 2005)
Stay tuned, read the document, feel free to comment below, there is much to discuss around this…
EDIT: This conversation has continued in the following entries (in order):