Tetrasargltones A and B, Fully Helically Polymerized Lindenane Sesquiterpenoid Tetramers from Sarcandra glabra

Tetrasargltones A and B (1 and 2, respectively), representing the first examples of lindenane sesquiterpenoid (LS) tetramers, were isolated from Sarcandra glabra. Their structures were fully elucidated via HR-MS and NMR, with their authenticity further confirmed by X-ray diffraction. Structurally, 1 and 2 possess two unprecedented fully helically polymerized carbon skeletons, which are formed through plausible sequential Diels–Alder cycloadditions at different sites of the triene LS precursor. Biologically, 1 and 2 exhibit cytotoxic activity against five cancer cell lines, with 2 showing the best activity in HCT116 cells (IC50 = 2.51 ± 0.13 μM) and exerting its cytotoxic effects through NF-κB pathway inhibition.