Spiroschincarins A–E: Five Spirocyclic Nortriterpenoids from the Fruit of Schisandra incarnata

Spiroschincarins A–E (1–5), five novel spirocyclic schinortriterpenoids featuring a unique 1-oxaspiro[6.6]tridecane motif, were isolated from the fruit of Schisandra incarnata. Their structures with absolute configurations were determined by extensive spectroscopic analyses, single-crystal X-ray diffractions, and experimental ECD (electronic circular dichroism). A hypothetical biogenetic pathway of 1–5 was postulated.