4.7. NMR Analysis of Drimane Sesquiterpenoids

The structures of compounds 1 to 4 were elucidated by 1D and 2D NMR. The ¹H- and ¹³C-NMR spectra were recorded in CDCl₃ solution in 5 mm tubes at RT on a Bruker Avance III 600 MHz spectrometer (Bruker Biospin GmbH, Rheinstetten, Germany) at 600.13 (¹H) and 150.61 (¹³C) MHz, with the deuterium signal of the solvent as the lock and TMS (for ¹H) or the solvent (for ¹³C) as internal standard. All spectra (¹H, ¹³C, gs-H, H–COSY, edited HSQC, and gs-HMBC) were acquired and processed with the standard Bruker software (TopSpin 4.x, Bruker, Germany).