Further examples of therapeutically relevant "larger" peptides are cyclopeptides, which have gained prominence as potential leads evolving from natural products-based drug discovery programs. Ecumicin is a tridecapeptide from a Nonomuraea spec. actinomycete with a promising bactericidal activity and new mechanism of action targeting Mycobacterium tuberculosis proteostasis via the ClpC1 chaperone protein. The HNMR spectrum of this 1,599 amu molecule was fully assigned to the level of lines (and underlying transitions) in 2016 . This knowledge was used to deduce the structures of five new congeners (nor-and deoxy-analogues) via HNMR spectroscopy only, as samples were very limited at the time. These structures were subsequently verified by full 2D NMR using micro-cryoprobe NMR analysis at 750 MHz . These examples have in common that QM-based spectroscopic data interpretation not only enables the full understanding of the NMR spectra, but also demonstrates the distinct nature and modularity of the spectral features (Figures and). Collectively, these examples also highlight the feasibility of achieving this level of understanding with higher-amu compounds, thereby covering the important range up to ~2,000 amu of drug molecules and toxins.