The development of new drugs calls for large collections of diverse molecules with considerable complexity. Ring distortion of natural products provides an efficient and facile approach to access new architectures with intriguing biological activities, by harnessing their inherent complexity. In this study, such a strategy has been explored on an abundant C₁₉-diterpenoid alkaloid, deltaline, enabling the synthesis of 32 new derivatives bearing a broad spectrum of unique scaffolds. Extensive spectroscopic studies including X-ray crystallographic analyses strongly supported the structures of the obtained novel skeletons, which present comparable opportunities with the great contributions made by nature for discovery of new lead compounds.

Three new C₂₀-diterpenoid alkaloids, along with twenty-two known alkaloids, were isolated from the whole herbs of Delphinium tatsienense. The new alkaloids include a vakognavine-type C₂₀-diterpenoid alkaloid, designated as tatsienenseine A (1), and two hetisine-type C₂₀-diterpenoid alkaloids, designated as tatsienenseines B (2) and C (3). Their structures were elucidated by IR, HR-ESI-MS, 1D- and 2D-NMR analyses.

Three new diterpenoid alkaloids, along with eleven known alkaloids, were isolated from the whole herbs of Delphinium yunnanense. The new alkaloids include a rearranged-type C₁₉-diterpenoid alkaloid, named yunnanenseine A (1), and two hetisine-type C₂₀-diterpenoid alkaloids, named yunnanenseine B and C (2 and 3, resp.). Their structures were elucidated by detailed NMR-spectroscopic studies.

Further phytochemical investigation of the roots of Aconitum hemsleyanum var. circinatum resulted in the isolation of three new aconitine-type C₁₉-diterpenoid alkaloids, hemsleyanines E–G (1–3, resp.). The structures of these new alkaloids were elucidated on the basis of spectral data including 2D-NMR.

Further investigation on the roots of Aconitum piepunense led to the isolation of a novel bis-diterpenoid alkaloid designated as piepunine (1). Its structure was established by extensive interpretation of its 1D- and 2D-NMR data, high-resolution ESI-MS, and IR spectra. Piepunine represents the first example of an atisine–denudatine-type bis-diterpenoid alkaloids.

Trichocarpinine (1), the first hetidine–hetisine type bisditerpenoid alkaloid, was isolated from the whole herbs of Aconitum tanguticum var. trichocarpum. Its structure was determined by a combination of spectroscopic techniques, including HR-ESI-MS and 1D- and 2D-NMR experiments. Its plausible biogenetic pathway was proposed as well (Scheme).

Four new myrsinol diterpenes, proliferins A–D (1–4, resp.) were isolated from the EtOH extracts of the roots of Euphorbia prolifera, along with four known compounds, euphorprolitherin B (5), euphorprolitherin D (6), SPr5 (7), and 14-desoxo-3-O-propionyl-5,15-di-O-acetyl-7-O-nicotinoylmyrsinol-14β-acetate (8). Their structures were established on the basis of spectroscopic methods, including HR-ESI-MS, and 1D- and 2D-NMR techniques. The cytotoxicity of compounds 1, 3, and 4 against cancer cells was evaluated, with compound 1 being active against A2780 cancer cells.