Extended Data Figure 3: NMR spectra of the natural product lugdunin.

The two diastereomeric and interconvertible forms of lugdunin (see imine intermediate, Extended Data Fig. 4d) show distinctive sets of NMR signals with consistent patterns, which were assigned by two-dimensional NMR methods (COSY, HMBC, HSQC-DEPT, ROESY and TOCSY) and corroborated the thiazolidine heterocycle as a special feature of lugdunin. Chemical shifts (δ) are shown in p.p.m. a, ¹H NMR spectrum (600 MHz) of lugdunin in DMSO-d6 at 308 K. b, ¹³C NMR spectrum (150 MHz) of lugdunin in DMSO-d6 at 308 K. Atom numbering refers to full spectral assignment shown in Extended Data Table 1. c, Expansion of HMBC spectrum (heteronuclear multiple bond correlation) shows distinct correlations between the amino acid α-proton and the carbonyl C-atom of the respective amino acid. d, Expansion of ROESY spectrum (rotation frame nuclear Overhauser effect spectroscopy) shows short-ranged correlations through space between α-protons and amino acid amide protons. e, Taken together, HMBC (green arrows) and ROESY (double headed blue arrows) correlations allowed for a full sequential walk along the peptide backbone, which readily confirmed the amino acid sequence of both lugdunin diastereomers (the sequential walk is exemplarily shown for one diastereomer).