All other HMBC correlations support the deduced structure (Fig. 1). Compound 1 was thus identified as a new guaiane sesquiterpenoid, zedoaraldehyde.
The relative configuration of C-4 was defined as shown according to the similarity of the NMR data and same biosynthetic pathway with the previously isolated compound zedoardiol (11) from the same plant material, the relative configuration of which was established using X-ray single-crystal diffraction (Zhang et al., 2014).