Summary of DFT calculations coupled with current statistical and/or artificial neural network (ANN) methods to assist experimental NMR data in identifying diastereomeric structures

Glycosylated and Succinylated Macrocyclic Lactones with Amyloid-β-Aggregation-Regulating Activity from a Marine Bacillus sp.

“…When it is limited to deduce the configurations of organic compounds by application of NMR spectroscopic analysis and chemical derivatization methods, quantum mechanics-based computational approaches, including the advanced probabilistic methods including CP3 and DP4 calculations, can be utilized [ 21 ]. DP4 calculations were then applied to establish the absolute configuration for the remaining chiral centers of C-4, C-5, and C-21 [ 22 ].…”

Nuclear Magnetic Resonance

“…18 Sarotti et al 19 reported on further development of DP4þ method in order to design an universal and customized method used in combination with GIAO NMR results. Nazarski 20 reported on the identification of diastereomeric structures from NMR spectra using statistical and/or artificial neural network (ANN) methods. An improved statistical approach for conformational analysis from carbon-13 chemical shifts was proposed by Cotos-Ya ´n ˜ez et al 21 Colherinhas 22,23 updated atomic charge parameters of aliphatic as well as hydroxylic, sulfur-containing and amidic 24 amino acids in order to improve the performance of molecular modeling via MD þ DFT-GIAO-NMR calculations.…”

Structural Revision of the Stemona Alkaloids Tuberostemonine O, Dehydrocroomines A and B, and Dehydrocroomine

“…In conclusion, the reported structures of four Stemona alkaloids, namely, tuberostemonine O, dehydrocroomines A and B, and dehydrocroomine, were revised by means of a combination of spectroscopic analysis, NMR chemical shift calculations, and X-ray crystallography, which, together with recently reported cases, highlights a critical need to not only reevaluate previously proposed structures without solid proof but also pay greater attention to elucidating the structures of new members of this alkaloid family. As demonstrated in numerous studies, − including the present work, NMR calculations coupled with sophisticated mathematical analyses, such as DP4+, constitute a powerful and reliable approach to solve structural problems. In the pursuit of structural correctness for stereochemically complex small molecules such as Stemona alkaloids, proper and in-depth implementation of this computational tool is highly recommended, especially when classic X-ray crystallography is not feasible.…”