Pseudolaridimers A and B, hetero-cycloartane-labdane Diels-Alder adducts from the cone of Pseudolarix amabilis.

Pseudolaridimers A (1) and B (2), two unprecedented heterodimers formed via a [4 + 2] Diels-Alder cycloaddition between a cycloartane triterpenoid unit and a labdane diterpenoid unit, were isolated from the cones of Pseudolarix amabilis. Their structures were established by extensive analysis of HRESIMS and NMR spectra. The absolute configuration of 1 was determined by single crystal X-ray diffraction (CuK(α)) of its methyl esterified derivative. Pseudolaridimer A (1) showed strong cytotoxicity against HCT116, ZR-75-30, and HL-60 human tumor cell lines, with IC(50) values 9.62, 7.84, 8.29 μg/mL, respectively. Pseudolaridimer B (2) only exhibited potent inhibition against the HL-60 cell line with an IC(50) value of 7.50 μg/mL.