Throughout organic chemistry, and especially in natural products
(NPs), where new bioactive metabolites are frequently isolated
in minute, oen sub-milligram quantities, nuclear magnetic resonance (NMR) has become the primary tool for structure determination. Typically, practitioners “extract” the structural information from NMR spectra that were generated via Fourier Transformation (FT) of free induction decays (FIDs),which represent the actual (raw) spectroscopic data from the excited nuclear spins in the NMR experiment (“spin choreography”). The deduction of structural information entails not only human interpretation and viewpoints (Fig. 1), but commonly also involves a significant loss of information (e.g., signal phase, peak shape, and signal multiplicity in tabulated representations), which leads to the inability to reprocess the spectra ab initio and/or employ computational tools to derive additional information from the same experimental data. For example, extracting the complete information contained in the FID of the most basic and sensitive NMR experiment, 1D 1H NMR, can avoid the ubiquitous nondescript designation of “multiplet” and exemplifies the concept of exploiting raw NMR data for additional information (e.g., Section 3 Structure Revision). The importance of extracting all of the information contained in an experimental data set is exemplified by the simple analogy presented in (Section 1.2 Dimensionality and Completeness).
This community-driven review calls for a re-examination of NMR-based structural analysis of NPs and represents the logical next step in the NMR Raw Data Initiative that commenced in 2016. 1 The seven major rationales used to organize this text evolve from the urgent need for raw NMR data dissemination and are explained in Section 2 Introduction to the Organization of this Review. This led to the separation of the material into sections that cover chemical structure (Sections 3–5), analytical methodology (Sections 4–7), followed by applications and future perspectives (Sections 8–10) of raw NMR data. Located at the heart of the intent to promote the free dissemination of raw NMR data, Section 10 Conclusions & Outlook should be of particular interest to scientists increasing the use of NMR in NP research.