Schincalactones A and B, Two 5/5/6/11/3 Fused Schinortriterpenoids with a 13-Membered Carbon Ring System from Schisandra incarnata.

Two novel schinortriterpenoids (SNTs), schincalactones A (1) and B (2), featuring a unique 5/5/6/11/3 ring system, together with schincalide B (3), were isolated from Schisandra incarnata. Their structures were elucidated by detailed spectroscopic analysis, and the absolute configurations of 1 and 3 were confirmed by single-crystal X-ray diffraction. Compounds 1 and 2 possess a 13-membered carbon ring and are the first examples in the SNT family. Plausible biosynthetic pathways of 1-3 were postulated.